HIV

1. FUNDAMENTALS OF HIV AND AIDS By Apollo Musa EHS

2. Outline • Brief History, Epidemiology and Transmission of HIV • HIV Infection and Disease Progression • National Policies, Guidelines; Legal and Ethical Issues

3. BRIEF HISTORY, EPIDEMIOLOGY AND TRANSMISSION OF HIV • Why? :- to impart knowledge on the natural history, epidemiology, modes of HIV transmission, impact and legal and ethical implications of the HIV epidemic

4. Objectives Be able to:- • Outline the history of the HIV pandemic since the reported index cases • Describe the epidemiology of HIV at the global, regional and national level • Describe modes of HIV transmission and key risk factors • Discuss transmission of HIV and the known HIV types and subtypes • Describe the impact of HIV and AIDS in the community • Describe the legal and ethical implications of the HIV epidemic and national response

5. A Brief History of the HIV Pandemic • In 1981, young doctors in the United States of America recognized a previously unknown syndrome in a group of men having sex with men (MSMs). • The syndrome was characterized by Pneumocystis Carinii pneumonia, Kaposi’s sarcoma and generalized immune deficiency. • After two years of painstaking work, in 1983, researchers identified the cause of the syndrome as a retrovirus, Human immunodeficiency virus. • Before scientists came to an agreement on this new name, the causative virus was previously referred to as Lymphadenopathy associated virus (LAV), AIDS associated retrovirus (ARV) and human T-lymphotrophic virus III (HTLV-III). • In 1986, the Human Immunodeficiency Virus (HIV) was accepted as the international designation for the acquired immunodeficiency syndrome causing retrovirus.

6. A Brief History of the HIV Pandemic….. • The origin of HIV has remained steeped in controversy and several theories have put forward to explain its source. • It is postulated by some that HIV originated from a mutation of the simian immunodeficiency virus (SIV) found in primates in the tropical forests of the Congo in Central Africa. • This new virus then jumped species into man through unintended contamination of raw wounds during slaughter of the primates for food by the local communities. • This new virus then spread through the exchange of contaminated body fluids among humans.

7. HIV Epidemiology • Since the first cases of AIDS were reported in the USA in the Centres for Disease Control and Prevention (CDC)’s Morbidity and Mortality Report of 5th June 1981, HIV spread rapidly throughout out the world. It has touched countries and populations far and wide.

8. The Global Picture • Globally, HIV has left enormous devastation in its wake. AIDS is now the fourth biggest cause of death worldwide. • Many countries and communities have suffered untold losses in human resources and reduced economic productivity as a consequence. • It is estimated that there are about 33.2 million people living with HIV (PLHIV) throughout the world today. Cumulatively about 25 million people have died of AIDS worldwide since 1981, with an estimated 3.1million deaths occurring in 2010 alone. • Majority of those infected in the developed world are in the key populations (especially men having sex with men and intravenous drug users) and the developing countries mostly individuals in heterosexual relations. • Incidence throughout the world is estimated at 5 million.

9. HIV in Sub-Saharan Africa • The sub-Saharan African region is the hardest hit, with about 70% of the global number of PHIV living here. • There are currently about 23 million PLHIV in the region. • The region contributes nearly the same proportion of the 3.1 million deaths and 5 million new infections globally. • There about 12 million children orphaned by AIDS in sub-Saharan Africa and the number is expected to rise, in the absence of more accessible care and treatment for the infected, as the pandemic matures. • The HIV pandemic in SSA has a feminine character, with about 60% of all PLHIV being women. • South Africa has the largest absolute number of PLHIV in SSA, with an estimated 5 million; and Botswana with the highest HIV prevalence at 38%. Countries in Southern Africa have the highest relative HIV prevalence in SSA; and Uganda in the East African region has the highest prevalence at 6.4% (UNGASS, 2010).

10. HIV in Kenya • After index case reported in 1984, Kenya experienced a rapid spread of HIV throughout the country. The epidemic peaked in (year...) with the prevalence estimated at 14.7% at the time. • The policy makers and statisticians in the country back then, did question the national prevalence data and the methodology used to estimate the numbers. • The country was at the time using ANC surveillance data to undertake the estimation and it became abundantly clear that this cohort had a risk of HIV infection higher than the general population. • The pregnancy that sent the women in the cohort to the clinics for the ANC services was an indication they had had unprotected sex, and which predisposed them to risk of HIV infection. • This compelling insight did drive the country to, in addition, adopt population based surveys to estimate the national HIV prevalence. As expected with this new broadened approach, the first Kenya demographic survey and health survey (KDHS, 2003), which had an HIV indicator, put the national prevalence at 6.7%.

11. HIV in Kenya….. • The 2007 Kenya AIDS Indicator Survey (KAIS, 2007) put the country’s HIV prevalence at 7.1%; and the KDHS (2008) confirmed this. From this data, it is estimated that there are about 1.3 million Kenyans in the age bracket 15 – 64 years old who are PLHIV. Further, there are about 100, 000 Kenyans who get HIV infected, and half this number of PLHIV who die, every year (UNGASS, 2010). • The epidemic in Kenya, however, remains heterogeneous in its distribution with lower rates generally observed in rural communities compared to urban centres, but this is rising. The Kenyan epidemic has a feminine character with 60% of PLHIV being women. • The KAIS report indicated that a higher proportion of those infected in the 15- 64 year age category are women (8.7%Vs 5.6%). There are about 1.6 women infected for every man. • And in the age bracket between 15- 24 years, women are four times more likely to be HIV infected than their male counterparts (6.1% Vs1.5%) due to age-mixing; a phenomenon driven by the recognized culture of young women who tend to date older men.

12. HIV in Kenya……… • The young girls’ inability to negotiate for safer sex tends to put them at greater risk of HIV infection. In the 15 -64 age category, the female to male HIV prevalence is 8.2% Vs 5.5% in the rural areas, and 10.8% Vs 6.2% in the urban areas. The HIV prevalence among men in the rural areas is however increasing (KAIS, 2007). • Nearly two thirds of the 15 – 64 year olds who are PLHIV are in a union (married or cohabiting). Further, the KAIS report (2007) indicates that about ten percent (10%) of the monogamous married couples and 14% of the polygamous ones have one or more of the partners infected. • HIV prevalence among Kenyans who have multiple sexual partners is higher than for their monogamous counterparts (11% Vs 7%). Further analysis did show that, the HIV prevalence among the polygamous males was 15.9% in 2007 (KAIS, 2007), and that among the divorced and/or widowed women was also high at 17 – 21%.

13. HIV in Kenya………….. • A higher proportion of Kenyans between 30 – 34 years are currently infected with HIV than any other age category in the country. • The HIV prevalence rates also exhibit significant regional and rural/urban variations, with the average urban rate at about 9% and the rural at 7% among those in the15-64 year olds (KAIS, 2007). • In absolute numbers, nearly 70% of the 1.4 million people living with HIV are in the rural areas.

14. Modes of HIV transmission • HIV is transmitted when an uninfected individual comes into contacted with body fluids and/or tissues of a PLHIV. • The key modes of HIV transmission include: • unprotected sexual contact with an infected individual, • through contact and/or transfusion of contaminated blood to an uninfected individual and • from mother to child.

15. Sexual contact • Sexual transmission of HIV through the sexual route is responsible for over 80% of those infected in Kenya. • Any unprotected penetrative sex, be it vaginal or anal, in the absence of correct and consistent (male or female) condom has some risk of HIV infection if any of the partners is infected. • The risk an individual is exposed of getting HIV infected through the sexual route is largely dependent on their sexual practices and preferences. • Penetrative anal sex is associated with a threefold higher risk of HIV infection for the ‘receiving person’, if the penetrating sexual partner is infected, than with vaginal sexual intercourse. • The reason for this is most likely because of the associated breach of the mucosal barrier of the rectal area due to inherently lower lubricated related friction during intercourse allowing for easier transmission of virus, if the sexual partner is infected.

16. Sexual contact……. • Women are at higher risk of getting if they have unprotected vaginal sexual intercourse with a male PLHIV; and the converse is not true. A woman is at a higher risk of HIV infection in this context because of several factors including biological, and especially the fact that her vagina has a large surface area for the virus to gain entry and that she gets highly infectious semen deposited into her • A man is less likely to get HIV infected if he has vaginal sexual intercourse with an infected woman. Unless he has injuries on his penile shaft, as would be the case in the presence of other sexually transmitted diseases like genital herpes, or if he is not circumcised. If the skin of the penis is intact, the most likely route of viral entry is the urethra. The urethra has a relatively smaller surface area exposed, and when the man has been aroused it is bathed in seminal fluid conferring some additional protection.

17. Sexual contact………. • Recent studies in South Africa (2005), in Uganda and Kenya (2006) have shown that male circumcision is protective. • It does reduce the risk of HIV infection via the heterosexual route by about 60%. When a man gets circumcised, the foreskin is removed leaving the penis exposed and this allows the skin to get dry and thicken, providing greater protection. • It is important to remember that circumcision is just one factor, and that its protection/benefit may be dramatically reduced if one gets involved in frequent and high risk behavior, or does not take appropriate precautions such as embracing the correct and consistent use of condoms.

18. IV Drug Use • Intravenous drug use is common among some of the key populations especially in the developed world, accounting for about 5 – 10% of all HIV infections worldwide. • The practice is however fast taking root in the developing countries including among some of groups of people in urban centres in Kenya. • Interdiction of drug hauls, including heroin, by the Kenyan police is on the increase. • Those who abuse drugs tend to ‘shoot’ in groups and share needles, increasing significantly their own risk of infection if any person in the group is a PLHIV.

19. IV Drug Use…… • Data has shown that about 50% of IV drug users in Mombasa and 53% in Nairobi were HIV infected in 2005. • This clearly demonstrates that IV drug use is increasingly becoming an important route of HIV infection in Kenya, and may increase the risk HIV in the general population. • Blood-letting procedures, such as traditional male circumcision, if done with shared and poorly/un-sterilized instruments can increase the risk of HIV infection among the initiated youth.

20. Occupational Exposure to HIV infected Material/ specimens • The risk of occupational exposure to HIV infected body fluids is common particularly for health providers serving in high prevalence and resource poor settings where protective gear and infection control procedures are wanting. • Contamination of the mucous membrane or needle stick injuries during a procedure on an HIV patient or material can lead to infection. • Studies in the USA have put the risk of HIV infection at about 0.1% for a single mucous membrane exposure and 0.32% in the event of a needle stick injury.

21. Occupational Exposure to HIV infected Material/ specimens…………. • The risk of infection is higher for health providers, as stated earlier, are serving in areas where HIV prevalence is high, there is poor access to protective clothing and gloves, and where fewer eligible patients are on treatment. • Poor access to anti-retrovirals for the eligible patients is associated with high viral load and therefore accidental exposure of the health providers to the body fluids of PLHIV could lead to HIV infection. • Those accidentally exposed to potentially infectious body fluids from patients they are attending to should go on Post Exposure Prophylaxis (PEP) immediately or within two hours to ensure they get the full benefit.

22. Blood Transfusion • Worldwide, blood transfusion is blamed for about 3 to 5% of all HIV infections. Any persons who gets transfused with a unit of HIV contaminated blood will get infected, and especially if the viral load is high. • The individuals who infected through blood transfusion have rapid disease progression and often to AIDS earlier than those who get HIV through other modes of transmission. • The risk of HIV infection through this route of transmission has, especially for individuals getting transfusion in recognized health facilities, because screening of blood for HIV and Hepatitis has been scaled up over the last ten years in Kenya.

23. Mother to Child Transmission of HIV • Worldwide, the risk of HIV transmission from mother to child varies from 13 to 40%. In 2003, it was estimated that mother to child transmission of HIV in Kenya was about 30% according to the Kenya Demographic and Health Survey (KDHS, 2003). • While the estimated relative risk has declines significantly as more pregnant women seek antenatal care services and access skilled delivery, about 22% (or about 22,000 children) of the total incidence of HIV in Kenya is due to mother to child transmission (UNGASS, 2010). • The child’s risk of infection varies including with when the mother got infected (if she got infected before or during pregnancy) and her general health, and therefore her prevailing viral load; the mode of delivery; the absence or presence of elongated labour; and whether or not the child is breast-fed.

24. Mother to Child Transmission of HIV • About 60% of the children currently living with the virus got it from their mothers during delivery. A child’s risk of HIV infection is increased by presence of extended labor which often results in membrane rapture and release of the amniotic fluid. • This rapture of the protective membrane allows direct contact of the baby with its mother’s potentially highly infectious blood and vaginal secretions. • Any injuries the child may suffer during its forced exit may results in contamination of the wounds with potentially infectious blood and vaginal secretions, significantly increasing their risk of infection.

25. Risk Factors that Increase an Individual’s vulnerability to HIV infection and/or transmission Biological Factors • Biological factors can increase an individual’s risk of HIV infection and/or transmission. These include infectiousness of the host of the virus, susceptibility of the potential recipient, and viral properties. Infectiousness of host • High viral load during the initial stage of infection and at the stages of the disease increase the risk of HIV transmission. High levels of virus in semen and genital secretions, as well as genital ulcers, menstruation, and trauma during sexual contact increase the risk of transmission. Breastfeeding by a HIV-positive mother increases their risk of passing on the virus to their young children through vertical transmission.

26. Risk Factors that Increase an Individual’s vulnerability to HIV infection and/or transmission… Susceptibility of recipient • Inflammation or disruption of the genital or rectal mucosa increases the risk of HIV infection if sexual partners engage in unprotected intercourse. Lack of circumcision in men having unprotected penetrative sexual intercourse with PLHIV female partners increase s his risk of HIV acquisition. • Male circumcision reduces risk of HIV infection from heterosexual encounter if other factors are held constant). Unprotected heterosexual intercourse during menstruation increases a woman’s risk of infection, and so does the presence of an ulcerative or non-ulcerative sexually transmitted disease around her genitals.

27. Risk Factors that Increase an Individual’s vulnerability to HIV infection and/or transmission… Viral properties • A mutant virus and/or resistant strain resulting from either the prevailing environmental conditions and/or sub-optimal exposure to antiretrovirals may be more virulent. Socioeconomic factors • Some of the socioeconomic factors known to heighten the risk of infection include social mobility that is accelerating with increasing globalization. More people are travelling and working away from home. • The HIV pandemic and epidemic do follow the routes of trade and commerce. For example, truck drivers who follow these trade routes may get infected after having unprotected sexual intercourse with sex workers, and transmit the virus to their wives, who in turn pass it along to their infants in utero- or through breast milk.

28. HIV subtypes • There are two types of HIV, namely HIV-1 and HIV-2. Worldwide, the predominant virus is HIV-1, and which is both more infectious than HIV-2 and those that it infects succumb to AIDS in about 12 years unless they are put on effective treatment. • Transmission of both types of virus is the same: via unprotected sexual contact with an infected individual, through contact and/or transfusion of contaminated blood, and from mother to child. • They both appear to cause clinically indistinguishable syndrome as the diseases progresses after infection However, HIV-2 is transmitted less easily, and the period between initial infection and illness is longer than the cases is for HIV-1.

29. HIV subtypes…… • Because of its high rate of replication, HIV-1 mutates rapidly, and therefore there are about 10 known genetically distinct subtypes (mutants) of HIV-1 within the major group (Group M). • The known subtypes are alphabetically named - A to J. In addition, Group O (the Outliers) has a distinct group of very heterogeneous viruses.

30. HIV subtypes…… • These subtypes are unevenly distributed throughout the world as highlighted below: • Subtype B: is found mostly in the Americas, Japan, Australia, the Caribbean, and Europe • Subtypes A and D: predominantly found in sub-Saharan Africa • Subtype C: largely found in South Africa and India • Subtype E: more common in the Central African Republic, Thailand, and other countries of Southeast Asia • Subtypes F (Brazil and Romania), G, and H (Russia and Central Africa), I (Cyprus), and O (Cameroon) and are associated with very low prevalence • All the subtypes are present in Africa, but with subtype B being less prevalent.

31. Case Study # 1 - Impact of the HIV Epidemic on the Health Sector in Kenya • It is a known fact that HIV has had a significant impact on the Health Sector in Kenya. • As part of group work, seek out relevant sources of information (national reports, policies and strategic plans)

32. Assignment • Write a short essay on Legal and ethical Issues associated with HIV epidemic and the National HIV response. • This assignment is to be handed in during the next session.

33. HIV INFECTION AND DISEASE PROGRESSION • Why? • To enable students to learn and understand the effects of HIV at different stages post infection.

34. Objectives • Describe the normal immune system. • Describe major components, the HIV life cycle and Immunology • Outline the WHO and CDC classification of HIV infection • Outline the phases of HIV infection • Discuss the effects of HIV on the immune system.

35. Introduction to the Immune System • The immune system protects the body by recognizing antigens or invading bacteria and viruses; and mounting a reaction towards them to protect the body from danger. • When the immune system is weakened or destroyed by a virus such as HIV, the body is vulnerable to opportunistic infections. • The immune system consists of lymphoid organs and tissues, including the bone marrow, thymus gland, lymph nodes, spleen, tonsils, adenoids, appendix, blood and lymphatic vessels

36. The HIV Lifecycle and Immunology • The Human Immunodeficiency Virus (HIV) is a retrovirus belonging to the family of lentiviruses. • Retroviruses have the ability to use their RNA and host DNA to make viral DNA and are known for their long incubation periods. • Like other retroviruses, HIV infects the human body, has a long incubation period (clinical latency), and ultimately causes the signs and symptoms of AIDS. • HIV causes severe damage to the immune system and eventually destroys it. • It accomplishes this by utilizing the DNA of CD4+ cell to replicate itself. In that process, the virus destroys the CD4+ cell.

37. The HIV Life Cycle The HIV lifecycle can be divided into six phases: binding and entry, reverse transcription, integration, replication, viral assembly, and budding as elaborated below: Binding (attachment) and entry • The HIV envelope proteins, gp120 and gp41, bind to receptors and co-receptors on the outside of the CD4+ cell. • The joining of the proteins and the receptors results in the fusion of the HIV membrane with the CD4+ cell membrane thereby allowing viral penetration of the CD4+ cell to occur. • During this process, CD4+ cell enzymes interact with the core of the HIV and stimulate the release of viral RNA into the cytoplasm of the CD4+ cell as well as the release of the viral enzymes, namely the i) reverse transcriptase, ii) integrase, and iii) protease. Reverse transcription • The HIV- RNA must be converted to a viral DNA strand before it can be incorporated into the DNA of the CD4+ cell. • This incorporation is required for the virus to multiply. • The conversion of HIV- RNA to viral DNA is known as the process of reverse transcription and is mediated by the HIV enzyme, reverse transcriptase. • The result is the production of a single strand of DNA from the viral RNA. • The single strand of this new DNA then undergoes replication into double-stranded HIV-DNA.

38. The HIV Life Cycle………….. Integration • Once reverse transcription has occurred, the viral DNA can now enter the nucleus of the CD4+ cell. The viral enzyme, integrase, then inserts the viral DNA into the CD4+ cell’s DNA. This process is known as integration. The CD4+ cell has now been changed into a “machine” used to produce more HIV. Replication • After successful integration of the viral DNA (called a provirus), the host cell is now latently infected with HIV. When the immune cell becomes activated, the provirus instructs the cellular machinery to produce the necessary components of HIV. • From the viral DNA, two strands of RNA are constructed: i) one strand is translated into HIV subunits such as protease, reverse transcriptase, integrase and structural proteins; and ii) the second strand becomes the genetic material for the new viral particles.

39. The HIV Life Cycle………….. Viral Assembly • All the components, or subunits, necessary to infect other CD4+ cells are available, but cannot do so until they have been assembled into new viruses. • During this process, the HIV protease enzyme cuts the produced long HIV proteins into smaller functional units which then get reassembled to form new virions. • The virions are now ready to infect other human cells. Budding • The HIV proteins, viral RNA, and all other components needed to make a new virus, are pushed close to the CD4+ cell membrane where they are assembled into new viruses. • The new virus particles push through the cell wall by budding. Many viruses can push through the wall of one CD4+ cell. • These new viruses leave the CD4+ cell and enter into circulation ready to infect other CD4+ cells.

40. WHO Classification System for HIV-Infected Adults and Adolescents The WHO has provided specific criteria for the classification of manifestations of HIV infection. This classification has been used to grade the disease progression and inform the time to start ART.

43. The Phases of HIV Disease Progression Generally, four phases of HIV disease are recognized. These are i) the acute phase, ii) the asymptomatic phase, iii) the symptomatic phase, and iv) the late symptomatic phase. Acute phase (initial infection) • As soon as HIV enters the body, it replicates rapidly. • This rapid replication requires energy from the host’s body. • The virus relies entirely on the host for survival and will access from the host whatever is required for its multiplication and survival. • The HIV infection may have a rapid onset, leading to hypermetabolism with catabolism. • Although some PLHIV may not have any symptoms at this stage, the host’s energy and nutrient requirements increase significantly, and therefore their food intake ideally should increase accordingly. • This period varies from 1 to 6 weeks.

44. Acute phase (initial infection)………….. • After the first six (sometimes up to 12) weeks, levels of the virus decrease, as the body produces antibodies to fight it (sero-conversion). • The body needs additional energy to cope with the infection and begins to hydrolyse its fat stores and muscle. • The hydrolysed muscle is used to repair the cellular and damaged tissue. • If the additional energy and nutrients needed are not provided to the body in earnest, the host loses weight and gradually develops malnutrition that weakens the immune system making the host vulnerable to opportunistic infections. • Without symptoms, as often is the case, the stage of initial infection with HIV goes un recognized and diagnosed.

45. Asymptomatic phase • The length of the asymptomatic phase of the HIV disease varies and may reach several years, depending on the health and nutritional status of the host prior to infection. • The asymptomatic phase is marked by hyper-metabolism and increased energy needs.

46. Symptomatic phase • Initial symptoms associated with HIV disease start at the onset of opportunistic infections. • The PLHIV presents with common symptoms such as fever, night sweats, tuberculosis, and fungal infection of the mouth, chronic diarrhea, and weight loss. • The onset of opportunistic infections is a sign of a weakened immune system. • Negative nitrogen balance occurs early in acute infections because of decreased food intake and increased urinary protein loss. • Immunologic response to HIV infection activates cytokines, which causes fever and anorexia, thereby leading to increased energy expenditure and decreased caloric intake. The opportunistic infections further increase the nutritional needs of the host and continue to weaken the immune system, speeding up the progression of the HIV disease. • Early immune failureoccurs when the persistence of symptoms and opportunistic infections lead to increased energy needs, reduced food intake, malabsorption of nutrients, weight loss, and wasting. The increased incidence of and sustained presence of these conditions are AIDS defining.

47. Symptomatic phase……. • Immunologic response to HIV infection activates cytokines, which causes fever and anorexia, thereby leading to increased energy expenditure and decreased caloric intake. • The opportunistic infections further increase the nutritional needs of the host and continue to weaken the immune system, speeding up the progression of the HIV disease. • Early immune failureoccurs when the persistence of symptoms and opportunistic infections lead to increased energy needs, reduced food intake, mal-absorption of nutrients, weight loss, and wasting. • The increased incidence of and sustained presence of these conditions are AIDS defining.

48. Late symptomatic phase (full-blown AIDS) • The late phase of the HIV disease progression is marked by metabolic alteration, significant weight loss, and wasting. • Other characteristics include fast rising viral load, a decreased CD4+ count, pneumonia, Kaposi’s sarcoma, systemic fungal infection, bacterial infections, and cancer. • At this stage the HIV infected individual is classified as having full blown AIDS. Unless the PLHIV is started on ART, death may occur at any time during this state of the HIV disease. • During the late stage, the common signs and symptoms include the development of life threatening infections and malignancies such as pneumonia, systemic fungal infection, bacterial infection and Kaposi’ sarcoma.

49. Effects of HIV on the immune system Primary Infection or Acute Retroviral Syndrome (Clinical Category) • Primary infection refers to the period of time when HIV first enters the body. At the time of primary infection with HIV, a person’s blood has a very high viral load. • The number of copies of virus per millilitre of plasma or blood can exceed 1,000,000. • The newly infected adult often experiences an acute retroviral syndrome. • Signs and symptoms of acute retroviral syndrome include fever, myalgia (muscle pain), headache, nausea, vomiting, diarrhoea, night sweats, weight loss, and rash. • These signs and symptoms usually occur two to four weeks after infection, subside after a few days, and often are misdiagnosed as influenza or infectious mononucleosis. • During primary infection, the CD4+ count in the blood decreases remarkably. • The virus largely targets the CD4+ cells in the lymph nodes and the thymus during this time, making the HIV-infected person vulnerable to opportunistic infections and limiting the thymus’s ability to produce T-lymphocytes. • HIV antibody testing using an enzyme-linked immunosorbent assay (ELISA) or enzyme immunoassay (EIA) may yield positive results.

50. Effects of HIV on the immune system………. Seroconversion with relative recovery • Sero-conversion refers to the period or time at which the body of the newly infected individual has produced enough antibodies in response to this external challenge to test HIV positive using ELISA (or any antibody) screening method. • After infection, the body tries to mount an immune response to beat the virus and the expressed antibodies are a consequence of this attempt by the individual’s immune system to fight. • Different individuals produce antibodies at varying rates depending on the character of their immune system and perceived risk of the antigen it is exposed to. • Some individuals will sero-convert within two weeks of exposure but the majority will have done so by the end of six weeks. • With the current anti-body based HIV test kits, the window period has been stated as six week. It therefore takes about six weeks to identify those who HIV infected using the antibody test in six weeks. • This phase of the HIV disease progression is characterized by development of some immunity against HIV, followed by a rapid decline in viremia and slowing down of CD4 cell loss.