pollution

Indoor air pollution and health
Scope of the problem

More than half of the world’s population rely on dung, wood, crop waste or coal to meet their most basic energy needs. Cooking and heating with such solid fuels on open fires or stoves without chimneys leads to indoor air pollution. This indoor smoke contains a range of health-damaging pollutants including small soot or dust particles that are able to penetrate deep into the lungs. In poorly ventilated dwellings, indoor smoke can exceed acceptable levels for small particles in outdoor air 100-fold. Exposure is particularly high among women and children, who spend the most time near the domestic hearth. Every year, indoor air pollution is responsible for the death of 1.6 million people - that's one death every 20 seconds.

The use of polluting fuels thus poses a major burden on the health of poor families in developing countries. The dependence on such fuels is both a cause and a result of poverty as poor households often do not have the resources to obtain cleaner, more efficient fuels and appliances. Reliance on simple household fuels and appliances can compromise health and thus hold back economic development, creating a vicious cycle of poverty.

According to the 2004 assessment of the International Energy Agency, the number of people relying on biomass fuels such as wood, dung and agricultural residues, for cooking and heating will continue to rise. In sub-Saharan Africa, the reliance on biomass fuels appears to be growing as a result of population growth and the unavailability of, or increases in the price of, alternatives such as kerosene and liquid petroleum gas. Despite the magnitude of this growing problem, the health impacts of exposure to indoor air pollution have yet to become a central focus of research, development aid and policy-making.
The health impact: A major killer

The World Health Organization (WHO) has assessed the contribution of a range of risk factors to the burden of disease and revealed indoor air pollution as the 8th most important risk factor and responsible for 2.7% of the global burden of disease . Globally, indoor air pollution from solid fuel use is responsible for 1.6 million deaths due to pneumonia, chronic respiratory disease and lung cancer, with the overall disease burden (in Disability-Adjusted Life Years or DALYs, a measure combining years of life lost due to disability and death) exceeding the burden from outdoor air pollution five fold. In high-mortality developing countries, indoor smoke is responsible for an estimated 3.7% of the overall disease burden, making it the most lethal killer after malnutrition, unsafe sex and lack of safe water and sanitation.

Indoor air pollution has been associated with a wide range of health outcomes, and the evidence for these associations has been classified as strong, moderate or tentative in a recent systematic review. Included in the above assessment were only those health outcomes for which the evidence for indoor air pollution as a cause was classified as strong. There is consistent evidence that exposure to indoor air pollution increases the risk of pneumonia among children under five years, and chronic respiratory disease and lung cancer (in relation to coal use) among adults over 30 years old. The evidence for a link with lung cancer from exposure to biomass smoke, and for a link with asthma, cataracts and tuberculosis was considered moderate. On the basis of the limited available studies, there is tentative evidence for an association between indoor air pollution and adverse pregnancy outcomes, in particular low birth weight, or ischaemic heart disease and nasopharyngeal and laryngeal cancers.

While the precise mechanism of how exposure causes disease is still unclear, it is known that small particles and several of the other pollutants contained in indoor smoke cause inflammation of the airways and lungs and impair the immune response. Carbon monoxide also results in systemic effects by reducing the oxygen-carrying capacity of the blood.
Pneumonia and other acute lower respiratory infections

Globally, pneumonia and other acute lower respiratory infections represent the single most important cause of death in children under five years. Exposure to indoor air pollution more than doubles the risk of pneumonia and is thus responsible for more than 900 000 of the 2 million annual deaths from pneumonia.
Chronic obstructive pulmonary disease

Women exposed to indoor smoke are three times as likely to suffer from chronic obstructive pulmonary disease (COPD), such as chronic bronchitis, than women who cook and heat with electricity, gas and other cleaner fuels. Among men, exposure to this neglected risk factor nearly doubles the risk of chronic respiratory disease. Consequently, indoor air pollution is responsible for approximately 700 000 out of the 2.7 million global deaths due to COPD.
Lung cancer

Coal use is widespread in China and cooking on open fires or simple stoves can cause lung cancer in women. Exposure to smoke from coal fires doubles the risk of lung cancer, in particular among women who tend to smoke less than men in most developing countries. Every year, more than one million people die from lung cancer globally, and indoor air pollution is responsible for approximately 1.5% of these deaths.
Disproportionate impacts on children and women

Household energy practices vary widely around the world, as does the resultant death toll due to indoor air pollution. While more than two-thirds of indoor smoke deaths from acute lower respiratory infections in children occur in WHO's African and South East Asian Regions, over 50% of the COPD deaths due to indoor air pollution occur in the Western Pacific region.

In most societies, women are in charge of cooking and - depending on the demands of the local cuisine - they spend between three and seven hours per day near the stove, preparing food. 59% of all indoor air pollution-attributable deaths thus fall on females. Young children are often carried on their mother's back or kept close to the warm hearth. Consequently, infants spend many hours breathing indoor smoke during their first year of life when their developing airways make them particularly vulnerable to hazardous pollutants. As a result, 56% of all indoor air pollution-attributable deaths occur in children under five years of age.

In addition to the health burden, fuel collection can impose a serious time burden on women and children. Alleviating this work will free women's time for productive endeavours and child care, and can boost children's school attendance and time for homework.
Millennium Development Goals are guiding international action

Tackling indoor air pollution in the context of household energy is linked to achieving the Millennium Development Goals, in particular to reducing child mortality (Goal 4), to promoting gender equality and empowering women (Goal 3), to opening up opportunities for income generation and eradicating extreme poverty (Goal 1), and to ensuring environmental sustainability (Goal 7). WHO reports the "proportion of the population using solid fuels for cooking" as an indicator for assessing progress towards the integration of the principles of sustainable development into country policies and programmes. Yet, the central role of household energy is not currently reflected in the political responses to achieve the Millennium Development Goals.

Measures to reduce indoor air pollution and associated health effects range from switching to cleaner alternatives, such as gas, electricity or solar energy, to improved stoves or hoods that vent health-damaging pollutants to the outside, to behavioural changes. There is an urgent need to investigate which interventions work and how they can be implemented in a successful, sustainable and financially viable way.
What WHO is doing

WHO, as the global public health agency, is advocating for the integration of health in international and national energy policies and programmes. WHO collects and evaluates the evidence for the impact of household energy on health and for the effectiveness of interventions in reducing the health burden on children, women and other vulnerable groups. WHO's programme on household energy and health rests on four pillars:

* Documenting the health burden of indoor air pollution and household energy: WHO will provide a regular update of the links between household energy and health and, where feasible, offer support to key research undertakings.
* Evaluating the effectiveness of technical solutions and their implementation: Developing simple tools for monitoring the effectiveness of interventions in improving health and building the capacity to conduct such evaluations will help generate much needed information from ongoing small- and large-scale projects. This information will provide the basis for the development of a catalogue of options that review both the effectiveness of interventions, and lessons learnt in relation to their implementation.
* Acting as the global advocate for health as a central component of international and national energy policies: Ultimately, policy-makers will want to know whether it pays off to invest in large-scale operations to reduce indoor air pollution. In terms of health, a recent cost-effectiveness analysis of different interventions suggests that improved stoves and switching to kerosene and gas represent cost-effective solutions. In addition, WHO is working on a cost-benefit analysis of interventions that - beyond health - will take into account all the benefits associated with improved household energy practices.
* Monitoring changes in household energy habits over time: Information about the energy habits of poor, mostly rural households is scarce and WHO has the responsibility to work towards progress in this area and to report, on a yearly basis, the Millennium Development Goal Indicator 29 "percentage of population using solid fuels".

Key partners include the Partnership for Clean Indoor Air, the United Nations Environment Programme, the United Nations Development Programme and the World Bank as well as many research institutions and non-governmental agencies around the world. WHO is already actively taking part in projects in several developing countries, including the most sophisticated scientific indoor air pollution study to date undertaken in Guatemala, and work in China, Lao People's Democratic Republic, Mongolia, Nepal, Kenya and Sudan. In the future, work will focus even more on those countries and populations most in need.

For more information contact:
WHO Media centre
Telephone: +41 22 791 2222
E-mail: mediainquiries@who.int

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HIV updates

Global AIDS epidemic continues to grow
New data also show HIV prevention programmes getting better results if focused on reaching people most at risk and adapted to changing national epidemics

GENEVA, 21 NOVEMBER 2006 -- The global AIDS epidemic continues to grow and there is concerning evidence that some countries are seeing a resurgence in new HIV infection rates which were previously stable or declining. However, declines in infection rates are also being observed in some countries, as well as positive trends in young people's sexual behaviours.

Report in English
:: Full report [pdf 2.21Mb]
:: Acknowledgements [pdf 220kb]
:: Global summary [pdf 99kb]
:: Introduction [pdf 295kb]
:: Sub-Saharan Africa [pdf 261kb]
:: Asia [pdf 384kb]
:: Eastern Europe and Central Asia [pdf 236kb]
:: Caribbean [pdf 92kb]
:: Latin America [pdf 92kb]
:: North America, Western and Central Europe [pdf 148kb]
:: Middle East and North Africa [pdf 67kb]
:: Oceania [pdf 67kb]
:: Maps [pdf 448kb]

Report in languages
:: French [pdf 2.80Mb]
:: Russian [pdf 2.84Mb]
:: Spanish [pdf 2.61Mb]

Press release in languages
:: Full story

Fact sheets in English
:: Global numbers [pdf 48kb]
:: Sub-Saharan Africa [pdf 51kb]
:: Asia [pdf 51kb]
:: Caribbean [pdf 50kb]
:: Eastern Europe and Central Asia [pdf 44kb]
:: Latin America [pdf 51kb]
:: Middle East and North Africa [pdf 47kb]
:: North America, Western and Central Europe [pdf 49kb]
:: Oceania [pdf 47kb]
:: Backgrounder on methodology [pdf 101kb]
:: Slides and graphs [pdf 204kb]

Fact sheets in languages
:: French [zip 2.45Mb]
:: Russian [zip 4.10Mb]
:: Spanish [zip 2.37Mb]

Related links
:: Play podcast - duration 00:03:14 [mp3 1.95Mb]
:: Global Fund press release

According to the latest figures published today in the UNAIDS/WHO 2006 AIDS Epidemic Update, an estimated 39.5 million people are living with HIV. There were 4.3 million new infections in 2006 with 2.8 million (65%) of these occurring in sub-Saharan Africa and important increases in Eastern Europe and Central Asia, where there are some indications that infection rates have risen by more than 50% since 2004. In 2006, 2.9 million people died of AIDS-related illnesses.

New data suggest that where HIV prevention programmes have not been sustained and/or adapted as epidemics have changed—infection rates in some countries are staying the same or going back up.

In North America and Western Europe, HIV prevention programmes have often not been sustained and the number of new infections has remained the same. Similarly in low- and middle-income countries, there are only a few examples of countries that have actually reduced new infections. And some countries that had showed earlier successes in reducing new infections, such as Uganda, have either slowed or are now experiencing increasing infection rates.

“This is worrying—as we know increased HIV prevention programmes in these countries have shown progress in the past—Uganda being a prime example. This means that countries are not moving at the same speed as their epidemics,” said UNAIDS Executive Director Dr Peter Piot. “We need to greatly intensify life-saving prevention efforts while we expand HIV treatment programmes.”

HIV prevention works but needs to be focused and sustained

New data from the report show that increased HIV prevention programmes that are focused and adapted to reach those most at risk of HIV infection are making inroads.

Positive trends in young people's sexual behaviours—increased use of condoms, delay of sexual debut, and fewer sexual partners—have taken place over the past decade in many countries with generalized epidemics. Declines in HIV prevalence among young people between 2000 and 2005 are evident in Botswana, Burundi, Côte d’Ivoire, Kenya, Malawi, Rwanda, Tanzania and Zimbabwe.

In other countries, even limited resources are showing high returns when investments are focused on the needs of people most likely to be exposed to HIV. In China, there are some examples of focused programmes for sex workers that have seen marked increases in condom use and decreases in rates of sexually transmitted infections, and programmes with injecting drug users are also showing progress in some regions. And in Portugal, HIV diagnoses among drug injectors were almost one third (31%) lower in 2005, compared with 2001, following the implementation of special prevention programmes focused on HIV and drug use.

Addressing the challenges: Know your epidemic

In many countries, HIV prevention programmes are not reaching the people most at risk of infection, such as young people, women and girls, men who have sex with men, sex workers and their clients, injecting drug users, and ethnic and cultural minorities. The report outlines how the issue of women and girls within the AIDS epidemic needs continued and increased attention. In sub-Saharan Africa for example, women continue to be more likely than men to be infected with HIV and in most countries in the region they are also more likely to be the ones caring for people infected with HIV.

According to the report, there is increasing evidence of HIV outbreaks among men who have sex with men in Cambodia, China, India, Nepal, Pakistan, Thailand and Viet Nam as well as across Latin America but most national AIDS programmes fail to address the specific needs of these people. New data also show that HIV prevention programmes are failing to address the overlap between injecting drug use and sex work within the epidemics of Latin America, Eastern Europe and particularly Asia.

"It is imperative that we continue to increase investment in both HIV prevention and treatment services to reduce unnecessary deaths and illness from this disease,” said WHO Acting Director-General, Dr Anders Nordström. “In sub-Saharan Africa, the worst affected region, life expectancy at birth is now just 47 years, which is 30 years less than most high-income countries."

The AIDS Epidemic Update underlines how weak HIV surveillance in several regions including Latin America, the Caribbean, the Middle East, and North Africa often means that people at highest risk—men who have sex with men, sex workers, and injecting drug users—are not adequately reached through HIV prevention and treatment strategies because not enough is known about their particular situations and realities.

The report also highlights that levels of knowledge of safe sex and HIV remain low in many countries, as well as perception of personal risk. Even in countries where the epidemic has a very high impact, such as Swaziland and South Africa, a large proportion of the population do not believe they are at risk of becoming infected.

“Knowing your epidemic and understanding the drivers of the epidemic such as inequality between men and women and homophobia is absolutely fundamental to the long-term response to AIDS. Action must not only be increased dramatically, but must also be strategic, focused and sustainable to ensure that the money reaches those who need it most,” said Dr Piot.

The annual AIDS Epidemic Update reports on the latest developments in the global AIDS epidemic. With maps and regional estimates, the 2006 edition provides the most recent estimates on the epidemic’s scope and human toll and explores new trends in the epidemic’s evolution. The report is available at www.unaids.org

UNAIDS, the Joint United Nations Programme on HIV/AIDS, brings together the efforts and resources of ten UN system organizations to the global AIDS response. Cosponsors include UNHCR, UNICEF, WFP, UNDP, UNFPA, UNODC, ILO, UNESCO, WHO and the World Bank. Based in Geneva, the UNAIDS Secretariat works on the ground in more than 75 countries worldwide.

As the directing and coordinating authority on international health work, the World Health Organization (WHO) takes the lead within the UN system in the global health sector response to HIV/AIDS. WHO provides technical, evidence-based support to Member States to help strengthen health systems to provide a comprehensive and sustainable response to HIV/AIDS including treatment, care, support and prevention services through the health sector.
http://www.who.int/hiv/mediacentre/news62/en/index.html

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Welcome 4G

4G is an initialism of the term Fourth-Generation Communications System. A 4G system will provide an end-to-end IP solution where voice, data and streamed multimedia can be served to users on an "Anytime, Anywhere" basis at higher data rates than previous generations. No formal definition is set as to what 4G is, but the objectives that are predicted for 4G can be summarized as follows:

4G will be a fully IP-based integrated system of systems and network of networks achieved after the convergence of wired and wireless networks as well as computer, consumer electronics, communication technology, and several other convergences that will be capable of providing 100 Mbit/s and 1 Gbit/s, respectively, in outdoor and indoor environments with end-to-end quality of service and high security, offering any kind of services anytime, anywhere, at affordable cost and one billing.[1]
Contents
* 1 Objectives
* 2 Wireless System Evolution
* 3 Components
o 3.1 Access schemes
o 3.2 IPv6
o 3.3 Advanced Antenna Systems
o 3.4 Software-Defined Radio (SDR)
* 4 Developments
* 5 Applications
* 6 Pre-4G Wireless Standards
* 7 References
* 8 See also
* 9 References

Objectives
4G is being developed to accommodate the quality of service (QoS) and rate requirements set by forthcoming applications like wireless broadband access, Multimedia Messaging Service, video chat, mobile TV, High definition TV content, DVB, minimal service like voice and data, and other streaming services for "anytime-anywhere". The 4G working group has defined the following as objectives of the 4G wireless communication standard:

* A spectrally efficient system (in bits/s/Hz and bit/s/Hz/site)[2],
* High network capacity: more simultaneous users per cell[3],
* A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R[1],
* A data rate of at least 100 Mbit/s between any two points in the world[1],
* Smooth handoff across heterogeneous networks[4],
* Seamless connectivity and global roaming across multiple networks[5],
* High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc)[5]
* Interoperability with existing wireless standards[6], and
* An all IP, packet switched network[5].

In summary, the 4G system should dynamically share and utilise network resources to meet the minimal requirements of all the 4G enabled users

Wireless System Evolution
First generation: Almost all of the systems from this generation were analog systems where voice was considered to be the main traffic. These systems could often be listened to by third parties. some of the standards are NMT, AMPS, Hicap, CDPD, Mobitex, DataTac

Second generation: All the standards belonging to this generation are commercial centric and they are digital in form. Around 60% of the current market is dominated by European standards. The second generation standards are GSM, iDEN, D-AMPS, IS-95, PDC, CSD, PHS, GPRS, HSCSD, and WiDEN.

Third generation: To meet the growing demands in the number of subscribers (increase in network capacity), rates required for high speed data transfer and multimedia applications, 3G standards started evolving. The systems in this standard are basically a linear enhancement of 2G systems. They are based on two parallel backbone infrastructures, one consisting of circuit switched nodes, and one of packet oriented nodes. The ITU defines a specific set of air interface technologies as third generation, as part of the IMT-2000 initiative. Currently, transition is happening from 2G to 3G systems. As a part of this transition, lot of technologies are being standardized. From 2G to 3G: 2.75G - EDGE and EGPRS, 3G - CDMA 2000,W-CDMA or UMTS (3GSM), FOMA, 1xEV-DO/IS-856, TD-SCDMA, GAN/UMA. Similarly from 3G to 4G: 3.5G - HSDPA, HSUPA, Super3G - HSOPA/LTE

Fourth generation: According to the 4G working groups, the infrastructure and the terminals of 4G will have almost all the standards from 2G to 4G implemented. Even though the legacy systems are in place to be adopted in 4G for the existing legacy users, going forward the infrastructure will however only be packet based, all-IP. Also, some proposals suggests to have an open platform where the new innovations and evolutions can fit. The technologies which are being called as 4G though not officially are as follows: WiMax, WiBro, 3GPP Long Term Evolution and 3GPP2 Ultra Mobile Broadband.

Components

Access schemes
As the wireless standards evolved, the access techniques used also exhibited increase in efficiency, capacity and scalability. The first generation wireless standards used plain TDMA and FDMA. In the wireless channels, TDMA proved to be less efficient in handling the high data rate channels as it requires large guard periods to alleviate the multipath impact. Similarly, FDMA consumed more bandwidth for guard to avoid inter carrier interference. So in second generation systems, one set of standard used the combination of FDMA and TDMA and the other set introduced a new access scheme called CDMA. Usage of CDMA increased the system capacity and also placed a soft limit on it rather than the hard limit. Date rate is also increased as this access scheme is efficient enough to handle the multipath channel. This enabled the third generation systems to used CDMA as the access scheme IS-2000, UMTS, HSXPA, 1xEV-DO, TD-CDMA and TD-SCDMA. The only issue with the CDMA is that it suffers from poor spectrum flexibility and scalability.

Recently, new access schemes like OFDMA, Single Carrier FDMA, Interleaved FDMA and MC-CDMA are gaining more importance for the next generation systems. WiMax is using OFDMA in the downlink and in the uplink. For the next generation UMTS, OFDMA is considered in the downlink. On the contrary, in the uplink IFDMA is considered since OFDMA contributes more to the PAPR related issues and results in nonlinear operation of amplifiers. IFDMA provides less power fluctuation and thus avoids amplifier issues. Similarly, MC-CDMA is in the proposal for IEEE 802.20 standard. These access schemes offer the same efficiencies as older technologies like CDMA. Apart from that, scalability and higher data rates can be achieved.

The other important advantage of the mentioned access techniques requires less complexity for equalization at the receiver. This is an added advantage especially in the MIMO environments since the spatial multiplexing transmission of MIMO systems inherently requires the high complexity equalization at the receiver.

In addition to improvements in these multiplexing systems, improved modulation techniques are being used. Whereas earlier standards largely used Phase-shift keying, more efficient systems such as 64QAM are being proposed for use with the 3GPP Long Term Evolution standards.

IPv6
Unlike 3G, which is based on two parallel infrastructures consisting of circuit switched and packet switched network nodes respectively, 4G will be based on packet switching only. This will require low-latency data transmission.

It is generally believed that 4th generation wireless networks will support a greater number of wireless devices that are directly addressable and routable. Therefore, in the context of 4G, IPv6 is an important network layer technology and standard that can support a large number of wireless-enabled devices. By increasing the number of IP addresses, IPv6 removes the need for Network Address Translation (NAT), a method of sharing a limited number of addresses among a larger group of devices.

In the context of 4G, IPv6 also enables a number of applications with better multi-cast, security, and route optimization capabilities. With the available address space and number of addressing bits in IPv6, many innovative coding schemes can be developed for 4G devices and applications that could aid deployment of 4G networks and services.

Advanced Antenna Systems
The performance of radio communications obviously depends on the advances of a antenna system. Recently, multiple antenna technologies are emerging to achieve the goal of 4G systems such as high rate, high reliability, and long range communications. In the early 90s, to cater the growing data rate needs of data communication, many transmission schemes were proposed. One technology, spatial multiplexing, gained importance for its bandwidth conservation and power efficiency. Spatial multiplexing involves deploying multiple antennas at the transmitter and at the receiver. Independent streams can then be transmitted simultaneously from all the antennas. This increases the data rate into multiple folds with the number equal to minimum of the number of transmit and receive antennas. This is called Multiple-input multiple-output communications (MIMO). Apart from this, the reliability in transmitting high speed data in the fading channel can be improved by using more antennas at the transmitter or at the receiver. This is called transmit or receive diversity. Both transmit/receive diversity and transmit spatial multiplexing are categorized into the space-time coding techniques, which does not necessary require the channel knowledge at the transmit. The other category is closed-loop multiple antenna technologies which use the channel knowledge at the transmitter.

[edit] Software-Defined Radio (SDR)

SDR is one form of open wireless architecture (OWA). Since 4G is a collection of wireless standards, the final form of a 4G device will constitute various standards. This can be efficiently realized using SDR technology, which is categorized to the area of the radio convergence.

Developments
The Japanese company NTT DoCoMo has been testing a 4G communication system prototype with 4x4 MIMO called VSF-OFCDM at 100 Mbit/s while moving, and 1 Gbit/s while stationary. NTT DoCoMo recently reached 5 Gbit/s with 12x12 MIMO while moving at 10 km/h,[7] and is planning on releasing the first commercial network in 2010.


An Irish fixed and wireless broadband company, Digiweb has announced that they have received a mobile communications license from the Irish Telecoms regulator, ComReg. This service will be issued the mobile code 088 in Ireland and will be used for the provision of 4G Mobile communications.[8] [9]


Pervasive networks are an amorphous and presently entirely hypothetical concept where the user can be simultaneously connected to several wireless access technologies and can seamlessly move between them (See handover, IEEE 802.21). These access technologies can be Wi-Fi, UMTS, EDGE, or any other future access technology. Included in this concept is also smart-radio (also known as cognitive radio technology) to efficiently manage spectrum use and transmission power as well as the use of mesh routing protocols to create a pervasive network.
Sprint plans to launch 4G services in trial markets by the end of 2007 with plans to deploy a network that reaches as many as 100 million people in 2008....
The German WiMAX operator Deutsche Breitband Dienste (DBD) has launched WiMAX services in Magdeburg and Dessau. The subscribers are offered two tariff plans. The first costing $12.99 per month offering 1 Mbit/s connection speed and 1 GB monthly traffic. The second plan has unlimited traffic, the speed increased to 2 Mbit/s for a $25.99 monthly fee. The subscribers are also charged $90.99 for the equipment and installation.[10] DBD received additional national licenses for WiMAX in December 2006 and have already launched the services in Berlin, Leipzig and Dresden.
American WiMAX services provider Clearwire made its debut on Nasdaq in New York on March 8, 2007. The IPO was underwritten by Merrill Lynch, Morgan Stanley and JP Morgan. Clearwire sold 24 million shares at a price of $25 per share. This adds $600 million in cash to Clearwire, and gives the company a market valuation of just over $3.9 billion.[11]

Applications
The killer application of 4G is not clear, though the improved bandwidths and data throughput offered by 4G networks should provide opportunities for previously impossible products and services to be released. Perhaps the "killer application" is simply to have mobile always on Internet, no walled garden and reasonable flat rate per month charge. Existing 2.5G/3G/3.5G phone operator based services are often expensive, and limited in application.
Already at rates of 15-30 Mbit/s, 4G should be able to provide users with streaming high-definition television. At rates of 100 Mbit/s, the content of a DVD, for example a movie, can be downloaded within about 5 minutes for offline access.

Fixed WiMax and Mobile WiMax are different systems, as of July 2007, all the deployed WiMax is "Fixed Wireless" and is thus not 4G.
# This page was last modified 09:25, 15 August 2007.
# All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.)
Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a US-registered 501(c)(3) tax-deductible nonprofit charity.

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DHF

Dengue/dengue haemorrhagic fever
- Impact of Dengue
- DengueNet
- Dengue activities
- Information resources

Dengue is the most common mosquito-borne viral disease of humans that in recent years has become a major international public health concern. Globally, 2.5 billion people live in areas where dengue viruses can be transmitted. The geographical spread of both the mosquito vectors and the viruses has led to the global resurgence of epidemic dengue fever and emergence of dengue hemorrhagic fever (dengue/DHF) in the past 25 years with the development of hyperendemicity in many urban centers of the tropics.

Transmitted by the main vector, the Aedes aegytpi mosquito, there are four distinct, but closely related, viruses that cause dengue. Recovery from infection by one provides lifelong immunity against that serotype but confers only partial and transient protection against subsequent infection by the other three. There is good evidence that sequential infection increases the risk of more serious disease resulting in DHF.

DHF was first recognized in the 1950s during the dengue epidemics in the Philippines and Thailand. By 1970 nine countries had experienced epidemic DHF and now, the number has increased more than fourfold and continues to rise. Today emerging DHF cases are causing increased dengue epidemics in the Americas, and in Asia, where all four dengue viruses are endemic, DHF has become a leading cause of hospitalization and death among children in several countries.

Currently vector control is the available method for the dengue and DHF prevention and control but research on dengue vaccines for public health use is in process. The global strategy for dengue /DHF prevention and control developed by WHO and the regional strategy formulation in the Americas, South-East Asia and the Western Pacific during the 1990s have facilitated identification of the main priorities: strengthening epidemiological surveillance through the implementation of DengueNet; accelerated training and the adoption of WHO standard clinical management guidelines for DHF; promoting behavioral change at individual, household and community levels to improve prevention and control; and accelerating research on vaccine development, host-pathogen interactions, and development of tools/interventions by including dengue in the disease portfolio of TDR (UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases) and IVR (WHO Initiative for Vaccine Research).

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Bird Flu

Key Facts About Avian Influenza (Bird Flu) and Avian Influenza A (H5N1) Virus
What You Should Know About Avian Flu
* Key Facts
* Infections in Humans
* Questions & Answers
* Current Situation

This fact sheet provides general information about avian influenza (bird flu) and information about one type of bird flu, called avian influenza A (H5N1), that has caused infections in birds and in humans. Also see Questions and Answers on the CDC website and Frequently Asked Questions (FAQs) on the World Health Organization (WHO) website.
Avian Influenza (Bird Flu)
Avian influenza in birds

Avian influenza is an infection caused by avian (bird) influenza (flu) viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.

Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions or with surfaces that are contaminated with secretions or excretions from infected birds. Domesticated birds may become infected with avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.

Infection with avian influenza viruses in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence. The “low pathogenic” form may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, the highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90-100% often within 48 hours.
Human infection with avian influenza viruses

There are many different subtypes of type A influenza viruses. These subtypes differ because of changes in certain proteins on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). There are 16 known HA subtypes and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds.

Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997. Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and has been limited, inefficient and unsustained.

“Human influenza virus” usually refers to those subtypes that spread widely among humans. There are only three known A subtypes of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among humans. It is likely that some genetic parts of current human influenza A viruses came from birds originally. Influenza A viruses are constantly changing, and they might adapt over time to infect and spread among humans.

During an outbreak of avian influenza among poultry, there is a possible risk to people who have contact with infected birds or surfaces that have been contaminated with secretions or excretions from infected birds.

Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress), and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the infection.
Studies done in laboratories suggest that some of the prescription medicines approved in the United States for human influenza viruses should work in treating avian influenza infection in humans. However, influenza viruses can become resistant to these drugs, so these medications may not always work. Additional studies are needed to demonstrate the effectiveness of these medicines.
Avian Influenza A (H5N1)

Influenza A (H5N1) virus – also called “H5N1 virus” – is an influenza A virus subtype that occurs mainly in birds, is highly contagious among birds, and can be deadly to them. H5N1 virus does not usually infect people, but infections with these viruses have occurred in humans. Most of these cases have resulted from people having direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces.
Avian influenza A (H5N1) outbreaks

For current information about avian influenza A (H5N1) outbreaks, see our Outbreaks page.
Human health risks during the H5N1 outbreak

Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 has caused the largest number of detected cases of severe disease and death in humans. However, it is possible that those cases in the most severely ill people are more likely to be diagnosed and reported, while milder cases go unreported. For the most current information about avian influenza and cumulative case numbers, see the World Health Organization (WHO) avian influenza website.

Of the human cases associated with the ongoing H5N1 outbreaks in poultry and wild birds in Asia and parts of Europe, the Near East and Africa, more than half of those people reported infected with the virus have died. Most cases have occurred in previously healthy children and young adults and have resulted from direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces. In general, H5N1 remains a very rare disease in people. The H5N1 virus does not infect humans easily, and if a person is infected, it is very difficult for the virus to spread to another person.

While there has been some human-to-human spread of H5N1, it has been limited, inefficient and unsustained. For example, in 2004 in Thailand, probable human-to-human spread in a family resulting from prolonged and very close contact between an ill child and her mother was reported. Most recently, in June 2006, WHO reported evidence of human-to-human spread in Indonesia. In this situation, 8 people in one family were infected. The first family member is thought to have become ill through contact with infected poultry. This person then infected six family members. One of those six people (a child) then infected another family member (his father). No further spread outside of the exposed family was documented or suspected.

Nonetheless, because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus one day could be able to infect humans and spread easily from one person to another. Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population. If H5N1 virus were to gain the capacity to spread easily from person to person, an influenza pandemic (worldwide outbreak of disease) could begin. For more information about influenza pandemics, see PandemicFlu.gov.

No one can predict when a pandemic might occur. However, experts from around the world are watching the H5N1 situation in Asia and Europe very closely and are preparing for the possibility that the virus may begin to spread more easily and widely from person to person.
Treatment and vaccination for H5N1 virus in humans

The H5N1 virus that has caused human illness and death in Asia is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza. Two other antiviral medications, oseltamavir and zanamavir, would probably work to treat influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.
For information about H5N1 vaccines, visit http://www.cdc.gov/flu/avian/gen-info/qa.htm.

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