The HIV AIDS Survelliance

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Prevalence of the Worldwide Epidemic

The estimated number of persons living with HIV worldwide in 2007 was 33.2 million, a reduction of 16% compared with the estimate published in 2006, 39.5 million (UNAIDS/WHO 2006). The single biggest reason for this reduction was the extensive surveillance completed in India which resulted in a major revision of that country's estimates. (Source: UNAIDS/WHO 2007)

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Every day, over 6,800 persons become infected with HIV.

Every day, over 5,700 persons die from AIDS, mostly because of lack of access to HIV prevention and treatment services.

Prevalence in Sub-Saharan Africa

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Sub-Saharan Africa continues to bear the brunt of the global epidemic with an infection prevalence of over 30% in some countries.

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68% of all people with HIV live in sub-Saharan Africa, with its epicenter in southern Africa.

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76% of all AIDS deaths in 2007 occurred in sub-Saharan Africa.

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61% of people living with HIV in sub-Saharan Africa are women.

Declines in national HIV prevalence are being observed in some sub-Saharan African countries, but such trends are currently neither strong nor widespread enough to diminish the epidemics¶ overall impact in this region. (Source: UNAIDS/WHO 2007)

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Within the region, southern Africa is the worst affected. National adult HIV prevalence exceeded 15% in eight southern Africa countries (Botswana, Lesotho, Mozambique, Namibia, South Africa, Swaziland, Zambia and Zimbabwe) in 2005.

Prevalence in the Caribbean

The Caribbean is the second-most affected region in the world. In the Caribbean,
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Some 230,000 people were living with HIV in 2007. An estimated 11,000 people died of AIDS-related illnesses. In addition 17,000 people were newly infected with HIV.

HIV prevalence is highest in the Dominican Republic and Haiti, which together account for nearly three quarters of all people living with HIV in the Caribbean. (Source: UNAIDS/WHO 2007)

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AIDS remains one of the leading causes of death in the Caribbean among people aged 25 to 44 years old. Prevalence in Asia: Decreasing Prevalence in Thailand

In Thailand, the number of new infections has fallen from a peak of 140,000 a year in 1991 to 21,000 in 2003. Thailand's epidemic has been changing over the years. There is evidence that HIV is now spreading largely among the spouses and partners of clients of female sex workers (FSWs) and among marginalized sections of the population, such as injecting drug users (IDUs). (Source: UNAIDS/WHO 2007)

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In 2007, an estimated 4.9 million people were living with HIV in Asia,

including the 440,000 people newly infected in the past year. Approximately 300,000 died from AIDS-related illnesses in 2007.

Thailand has made substantial progress in the fight against HIV/AIDS. It is one of the very first countries to achieve the sixth Millennium Development Goal, which is to begin to reverse the spread of HIV/AIDS by 2015. Factors that Affect HIV/AIDS Prevalence

Worldwide, a wide variety of factors account for the prevalence of HIV, including:
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High prevalence of sexually transmitted infections (STIs) Limited access to STI management Limited access to, or social non-acceptance of, condoms War and civil disturbance Cultural/ethnic practices Women¶s low status Low literacy rates Increasing urbanization, migration, and mobilization Low level of political commitment Exposure to blood from unsafe medical practices and/or traditional practices

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The main factor driving the HIV/AIDS epidemic in Africa is heterosexual sex.

The two main factors driving the HIV/AIDS epidemic in Asia are injection drug use and commercial sex. Basic HIV Facts and Surveillance Data

In determining the potential HIV surveillance needs and use of surveillance data, it is important to understand some basic facts about the biology, transmission, natural history, and prevention of HIV. As sero-surveillance relies upon biological specimens, it is important to know the biology and routes of transmission. By understanding the natural history we can describe ways to capture HIV infection information at different stages of disease. By understanding prevention, care, and treatment we can better design surveillance to assess the impact of these interventions. Biology: The Virus

Since AIDS was first recognized in 1981, extensive research has shown that HIV is the virus that causes AIDS. HIV is a retrovirus, a family of viruses that carry their genetic information on a single strand of RNA. HIV infects a number of different cells in the body. Most important are two classes of white blood cells that are involved with protecting the body against infection:
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CD4 lymphocytes Macrophages

As the number of these cells is depleted because of the virus, patients become immunodeficient, meaning their immune systems are insufficient to ward off infections. They develop opportunistic infections and certain cancers. Biology: HIV Types

Two major types of HIV have been recognized: HIV-1 and HIV-2.

The epidemiology of HIV subtype distribution and evolution worldwide are critical for several reasons:
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For vaccine development To trace transmission among individuals and track the spread of the virus through countries

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The greatest diversity of HIV strains has

been found in sub-Saharan Africa, which also has been the region most severely affected by the epidemic. How HIV Is Transmitted

Both HIV-1 and HIV-2 are transmitted in the same ways:
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The predominant route of transmission is through unprotected heterosexual intercourse or homosexual intercourse between men. HIV is also transmitted through blood, blood products, and donated organs (also referred to as parenteral transmission). HIV may be transmitted from an infected mother to her fetus or infant during pregnancy, delivery or when breastfeeding (also referred to as perinatal transmission).

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There are no documented cases of sexual transmission between women.

A number of factors increase the risk of becoming infected with HIV through sexual intercourse. These fall into two broad categories:
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Level of exposure Transmission-related factors

Level of exposure refers to the number of sexual partners and the risk of having an infected partner. Transmission-related factors include the viral load of the infected patient, type of intercourse, the coexistence of sexually transmitted infections (STIs), and failure to use prevention methods such as condoms

Type of intercourse Anal intercourse is riskier than vaginal intercourse, and vaginal intercourse is substantially riskier than oral intercourseViral load

The amount of HIV in the circulating blood. Also known as µviral burden¶ or µviral dose.
Natural History

AIDS is the late stage of HIV infection. AIDS is characterized by a severely weakened immune system that can no longer ward off life-threatening infections and cancers. The risk for AIDS is related to the length of HIV infection. The vast majority of HIV-infected individuals will eventually develop AIDS.
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Prior to the introduction and uptake of antiretroviral (ARV) therapy, the average time from HIV infection to onset of clinical AIDS in North American patients was 10 years. Duration between infection and onset of AIDS in sub-Saharan Africa is estimated to be one year shorter than in North America.

Prevention of Sexual Transmission

The best long-term solution for controlling the HIV/AIDS epidemic is a low-cost, highly effective vaccine, but one will not be available in the near future. Therefore, the best options remain changes in behavior and a handful of prevention technologies. The goal of prevention is to decrease the risk for HIV transmission from infected to uninfected individuals. The basic approach to prevention involves:

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Decreasing the risk of being exposed by avoiding sexual intercourse with an infected person Decreasing the risk of transmission, if exposed

The most basic approach to prevention, other than abstinence, is to:
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Delay age of sexual debut Decrease the number of sexual partners Consistently use male or female condoms Undergo voluntary testing and counseling to know your HIV status Identify and appropriately treat STIs

Prevention of Blood-Borne Transmission

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In some parts of Asia, the principal means of blood-borne transmission has been people who share needles and syringes when injecting illegal drugs.

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In Indonesia, around nine out of every 10 injectors said they had used a needle that had been previously used by someone else.

A short-course antiretroviral regimen given to the mother and the newborn baby can substantially reduce the risk of perinatal transmission of HIV during pregnancy and childbirth. HIV-positive mothers can avoid the risk of transmission through infected breast milk by using breast milk substitutes. However, significant health risks are associated with this practice:
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Malnutrition

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Exposure to other infections

For this reason, WHO/UNICEF/UNAIDS have developed several documents that address HIV and breastfeeding. Click here for a summary of their recommendations.

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Perinatal transmission, or HIV transmission during pregnancy, childbirth and breastfeeding, accounts for 10% of HIV transmission in sub-Saharan Africa.

Perinatal transmission accounts for very few cases of HIV/AIDS in Asia.

Treatment: Antiretroviral Drugs

Antiretroviral drugs are used to treat HIV infection. In the past, the high cost of these drugs made them rarely used in most developing countries. Several agencies are now making funds available for antiretroviral and other therapies. These organizations include the Global Fund to Fight AIDS, Tuberculosis and Malaria, the World Bank Multi-sectoral AIDS Plan (MAP) and the United States President¶s Emergency Plan for AIDS Relief (PEPFAR). There are three classes of antiretroviral drugs:
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Nucleoside reverse transcriptase inhibitors (NRTIs) Non-nucleoside reverse transcriptase inhibitors (nNRTIs) Protease inhibitors (PIs)

WHO recommends the following antiretroviral therapy strategy:
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First line drugs: 2 NRTI + 1 NNRTI Second line drugs: 2 NRTI + PI

Surveillance is an important tool to monitor drug resistance in populations on treatment.
Treatment: Preventing & Treating Opportunistic Infections

In addition to antiretroviral drugs, the treatment of HIV infection includes diagnosis, prophylaxis, and treatment of selected opportunistic infections.
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Anti-tuberculosis (TB) drugs extend the lives of patients with both HIV and TB. Cotrimoxazole prophylaxis has been used successfully to prevent the onset of opportunistic infections in HIV-positive patients in sub-Saharan Africa. Vaccines are available for some potential opportunistic infections, such as pneumococcal disease.

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