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| Introduction |
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| Epidemiology is the study of how often diseases occur
in different groups of people and why. The findings of
epidemiological studies can be used to plan programmes
for control of diseases; plan programmes for the treatment
of diseases; and to measure the effectiveness of the control
programmes. |
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| Clinical medicine looks at diseases in individuals.
Whereas, epidemiology studies diseases in defined communities.
Communities could be defined by common characteristics.
This common characteristic might be a shared profession
(for e.g. sex work) or area of residence (e.g. the entire
population of a state) or some other characteristic that
could define a community. Such communities, which are
identified for epidemiologic study, are called target
populations. |
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| When a target population is defined, the study further
identifies an appropriate subset of the target population.
This group is called study population and study sample
is drawn from the study population. |
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| Well-conducted epidemiological studies have kept a track
on how the HIV/AIDS epidemic is progressing in different
parts of the world. Epidemiological techniques also permit
different methods of forecasting the possible scenarios
in the future. Methodologically, sound forecasts permit
countries and programme-developers to be prepared well
in advance. |
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| Epidemiological studies can also narrow
down the cause of diseases and work in collaboration with
other branches of investigative medicine and unravel the
factor/s causing the disease. |
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| A high level of scientific rigour needs to go into the
design and conduct of epidemiologic studies. Such well-conducted
studies are of immense use in public health planning.
Scientific Epidemiology was born when John Snow through
systematic documentation of data, identified drinking
polluted water from one water pump as the cause of a cholera
outbreak in London and terminated the epidemic by blocking
water use from that particular water pump (1854). |
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| Significance
of Epidemiology in HIV/AIDS |
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| 1. Epidemiological Studies can be used
to assess the Total Number of HIV/AIDS Cases in a Country
(prevalence) |
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| Assessment of the total number of HIV/AIDS cases in
a country is important from many points of view. |
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- The assessment of HIV/AIDS cases in a country can
be used to bring 'visibility' to an invisible epidemic.
The findings can be used to convince policy makers
about the current status of the problem and the implications
of the current status for the future.
- Periodic assessments of the total number of HIV/AIDS
cases can be used to create forecasts of likely scenarios
for the future. This can help the policy makers and
programme development sectors to be prepared for the
emerging scenario.
- Assessment of HIV/AIDS cases can give a rough indicator
about the efficacy of the HIV control programmes.
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| 2. Epidemiological Studies can be used
to assess the New Cases Occurring During Defined Periods
of Time (Incidence) |
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| Incidence studies in HIV are complex to conduct. However,
incidence studies have been done using a variety of methodologies.
Incidence studies give a clear assessment of the new cases
happening over a defined period of time. Further, these
studies give a better indication of the efficacy of HIV
prevention programmes. |
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| 3. Epidemiological Techniques can be used
to Mount Surveillance Measures on the Epidemic. |
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| All well-managed HIV control programmes have set up
sensitive surveillance systems. These systems give periodic
information on a variety of indicators, which track different
aspects of the epidemic. |
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4. Epidemiological Techniques can Measure
the Efficacy of Drugs and Vaccines being
Developed |
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| Since the drug and vaccine development is an evolving
phenomenon, they need to be tested out in well-designed
and conducted trials. |
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| GLOBAL EPIDEMIOLOGY OF HIV/AIDS (SOURCE: UNAIDS - Joint
United Nations Programme on HIV/AIDS, "AIDS Epidemic Update
December 2000" and "Report on the global HIV/AIDS epidemic
June 2005". |
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| People Living With
HIV |
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| According to estimates from the Joint United Nations Programme on HIV/AIDS (UNAIDS) 40.3 million in total out of which adults are 38.0 million, women living with HIV are 17.5 millionand 2.3 million children were living with HIV at the end of 2005. |
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| Number of People Infected during 2005,
and the Number of Deaths |
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| During 2005, about 4.9 million people in total out of which 4.2 millions are adults and and 700,000 children became infected with the Human Immunodeficiency Virus (HIV), which causes AIDS. The year also saw 3.1 million deaths in total out of which 2.6 million are adults and 570,000 are childrens from HIV/AIDS- a high number despite antiretroviral therapy which staved off AIDS and AIDS deaths in the richer countries. |
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| Deaths among those already infected will continue to
increase for some years even if prevention programmes
manage to cut the number of new infections to zero. However,
with the HIV-positive population still expanding, the
annual number of AIDS deaths can be expected to increase
for many years. |
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| Young People and Children with HIV/AIDS and the AIDS Orphans |
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| Around half of all people who acquire HIV become infected before they turn 25 and typically die of the life-threatening illnesses called "AIDS" before their 35th birthday. This age factor makes AIDS uniquely threatening to children. According to the estimation of UNICEF,by the end of 2003, the epidemic had left behind around 24,200 AIDS orphans, defined as those having lost their mother or both parents before reaching the age of 15. |
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| In 2005, an estimated 700,000 children aged 15 or younger became infected with HIV. Over 90 percent were babies born to HIV-positive women, who acquired the virus at birth or through their mother's breast milk. Of these, almost nine-tenths were in sub-Saharan Africa. Africa's lead in mother-to-child transmission of HIV was firmer than ever despite new evidence that HIV ultimately impairs women's fertility: once infected, a woman can be expected to bear 20 percent fewer children than she otherwise would. |
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| HIV/AIDS around the
World |
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| The overwhelming majority of people with HIV, some 95 percent of the global total, live in the developing world. That proportion is set to grow even further as infection rates continue to rise in countries where poverty, poor health systems and limited resources for prevention and care fuel the spread of the virus. |
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| High-income Countries |
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| It is estimated that 0.3 million are living with HIV in these countries according to UNAIDS 2005. Overall, HIV prevalence has risen slightly in both regions, mainly because anti retroviral therapy is keeping HIV positive people alive longer. |
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| Sub-Saharan Africa |
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| In Africa, south of the Sahara desert, an estimated 3.2 million adults and children became newly infected with HIV during the year 2005, bringing the total number of people in the region living with HIV/AIDS to 25.8 million by the end of the year 2005. The number of people in total who became infected during the year 2005, was more than the year 2003 which was a total of 24.9 million. Declines in adult national HIV prevalence appear to be underway in three sub-Saharan African countries: Kenya, Uganda and Zimbabwe.1 With the exception of Zimbabwe, countries of southern Africa show little evidence of declining epidemics. HIV prevalence levels remain exceptionally high (except for Angola), and might not yet have reached their peak in several countries—as the expanding epidemics in Mozambique and Swaziland suggest. |
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| For the moment, overall HIV prevalence, the regional total of people living with HIV or AIDS continues to rise because there are still more newly infected individuals joining it each year than there are people leaving it through death. However, as people infected years ago succumb to HIV related illnesses (average survival in the absence of anti retroviral therapy is estimated at around 8-10 years), mortality from AIDS is increasing. AIDS deaths in 2005 totalled 2.4 million, as compared with 2.3 million in 2004. In the coming years, unless there is far broader access to life prolonging therapy, and providing that new infections do not start rising again, the number of surviving HIV positive Africans can be expected to stabilise and finally shrink, as AIDS increasingly claims the lives of those infected long ago. |
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| African women are considerably more likely - at least 1.2 times - to be infected with HIV than men. Among young people aged 15–24 years, an estimated 4.6% [4.2–5.5%] of women and 1.7% [1.3–2.2%] of men were living with HIV in 2005. There are a number of reasons why female prevalence is higher than male in this region, including the greater efficiency of male-to-female HIV transmission through sex and the younger age at initial infection for women. |
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| Eastern Europe and Central Asia |
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| The estimated number of adults and children living with HIV or AIDS in Eastern Europe and Central Asia was 1.6 million at the end of 2005. Some 270,000 people were newly infected with HIV in 2005. AIDS related deaths claimed an estimated 62,000 lives in 2005 alone as compared to 36,000 AIDS related deaths in the year 2003. |
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| Worst affected are the Russian Federation, Ukraine, and the BAltic States, and most recent epidemics are now evident in Kyrgystan and Uzbekistan. The actual number of total infections is much higher: an estimated 860 000 people (420 000–1 400 000) were living with HIV in the Russian Federation at the end of 2003 (UNAIDS, 2004). |
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| Asia |
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| About 8.3 million people in Asia are living with HIV in the year 2005, bringing to an estimated 1.1 million of people newly infected with the virus. A further 520,000 people are estimated to have died due to AIDS-related diseases in 2005. National adult HIV prevalence is 0.4 percent in the majority of the region's countries. However, the figure can be deceptive. There are signals of serious HIV outbreaks among certain populations of these countries and the large populations can translate into a large number of people living with the virus. |
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| Risky behaviour—often more than one form—continues to sustain serious AIDS epidemics in Asia. At the heart of many of Asia’s epidemics lies the interplay between injecting drug use and unprotected sex, much of it commercial. Yet prevention strategies still rarely re. ect the fact that such combinations of risk-taking exist in virtually every country in the region. As a result, many of the epidemics in Asia are in transition—including in those countries where the spread of HIV to date has been contained. |
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| North Africa and the Middle East |
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| The notion that this region has sidestepped the global HIV epidemic is not borne out by the latest estimates, which indicate that 67,000 people acquired HIV in 2005 alone, bringing to 510,000 the total number of people living with HIV/AIDS in the Middle East and North Africa. Around 58,000 people died of AIDS related diseases in 2003. There is the potential for a considerable rise in the number of HIV infections in this region. |
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| Although HIV surveillance remains weak in this region, more comprehensive information is available in some countries (including Algeria, Libya, Morocco, Somalia, and Sudan). Available evidence reveals trends of increasing HIV infections (especially in younger age groups) in such countries as Algeria, Libya, Morocco and Somalia. The main mode of HIV transmission in this region is unprotected sexual contact, although injecting drug use is becoming an increasingly important factor (and is the predominant mode of infection in at least two countries, Iran and Libya). |
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| Latin America and the Caribbean |
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| About 1.8 million people are now living with HIV in Latin America and about 300,000 in Caribbean. At least 24,000 people died of AIDS-related diseases in 2005 in Caribbean and about 66,000 died in Latin America. |
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| Primarily due to their large populations, the South American countries of Argentina, Brazil and Colombia are home to the biggest epidemics in between men, and men and women) and injecting drug use, with the role of sex between men in HIV transmission a more prominent factor than is commonly acknowledged. In nearly all the Latin American countries, the highest levels of HIV infection are being found among men who have sex with men. |
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| Whereas the Caribbean’s status shows the second-most affected region in the world masks substantial differences in the extent and intensity of its epidemics. Estimated national adult HIV prevalence surpasses 1% in Barbados, Dominican Republic, Jamaica and Suriname, 2% in the Bahamas, Guyana and Trinidad and Tobago, and exceeds 3% in Haiti. In Cuba, on the other hand, prevalence is yet to reach 0.2%. |
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| North America, Western and Central |
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| The number of people living with HIV in North America, Western and Central Europe rose to 1.9 million [1.3–2.6 million] in 2005, with approximately 65 000 people having acquired HIV in the past year. Wide availability of antiretroviral therapy has helped keep AIDS deaths comparatively low, at about 30 000. |
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| There were an estimated 1.04 million–1.2 million HIV cases in the USA at the end of 2003. The increase re. ects the fact that people with HIV are living longer due to antiretroviral treatment, as well as the failure to adapt and sustain the prevention successes achieved during the epidemic’s first 10–15 years. |
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| Oceania |
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| An estimated 74 000 people [45 000–120 000] in Oceania are living with HIV. Although less than 4000 [<10 000] people are believed to have died of AIDS in 2005, about 8200 [2400–25 000] are thought to have become newly infected with HIV. Among young people 15–24 years of age, an estimated 1.2% of women [0.6–2.4%] and 0.4% of men [0.2–0.8%] were living with HIV in 2005. |
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| More than 90% of the 11 200 HIV infections reported across the 21 Paci. c Islands countries and territories by end-2004 were recorded in Papua New Guinea where an AIDS epidemic is now in full swing. Since 1997, HIV diagnoses have increased by about 30% each year in Papua New Guinea; approximately 10 000 HIV cases had been diagnosed by the end of 2004, but the actual number of people living with HIV could be . ve times as high (National AIDS Council PNG and National Department of Health, 2004). The country’s HIV surveillance system reveals a prevalence of 2% among pregnant women attending antenatal clinics in Goroka in 2003 (compared with 0.9% in 2002), 2.5% in Lae and 1.4% in the capital of Port Moresby. |
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| The Future |
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| What is needed on a massive national and international
level is to: |
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- end the stifling silence that continues to surround
HIV in many countries,
- explode myths and misconceptions that translate
into dangerous sexual practices,
- expand prevention initiatives such as condom promotion
that can reduce sexual transmission,
- create conditions in which young children have the
knowledge and the emotional and financial support
to grow up free of HIV, and
- devote real money to providing care for those infected
with HIV and support to their families.
- Promote gender equality and address gender norms and relations to reduce the vulnerability of women and girls, involving men and boys in this effort.
- Promote programmes targeted at HIV prevention needs of key affected groups and populations.
- Review and reform legal frameworks to remove barriers to effective, evidence based HIV prevention, combat stigma and discrimination and protect the rights of people living with HIV or vulnerable or at risk to HIV.
- Ensure that sufficient investments are made in the research and development of, and advocacy for, new prevention technologies.
- Involve people living with HIV in the design, implementation and evaluation of prevention strategies, addressing the distinct prevention needs.
- Ensure that human rights are promoted, protected and respected and that measures are taken to eliminate discrimination and combat stigma.
- Support the mobilization of community based responses throughout the continuum of prevention, care and treatment.
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| A trail of successful responses has already been blazed by a small number of dedicated communities and governments. The challenge for everyone is to adapt and massively expand successful approaches that make it harder for the virus to spread, and that make it easier for those affected to live full and rewarding lives. |
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