One Of The Major Human Health Threats Biology Essay

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AIDS (Acquired Immune Deficiency Syndrome) is one of the major human health threat which is caused by HIV (human Immunodeficiency Virus). Humans are the only host for HIV. There are two genetic types of HIV which are known as HIV-1 and HIV-2. According to social worker professor Poindexter, the majority of infection is caused by HIV-1 in world wide, whereas HIV-2 is most common in West Africa. HIV-1 is one of the deadliest viruses that are accounted for taking millions of lives world wide. However the highest impact is recorded in underdeveloped nations of Sub-Saharan Africa. I was born and raised in Ethiopia, which is located in the Easter part of Africa. In Ethiopia HIV is one of the major public concerns among the population. Several studies and researches have done to understand the virus and to find out treatment and prevention methods. Based on the result of several scientific research and studies, this paper mainly focuses on HIV-1 classification, structure, life cycle, disease, treatment, and public health impact.

Based on Baltimore classification method HIV (Human Immunodeficiency Virus) is classified under class VI in a member of Genus lentivirus. Viruses classified in this genus have characteristics of long period of incubation and long duration illness (Card et al., 41). HIV is a retrovirus with distinctive structural and fictional characteristics. HIV is an enveloped virus which has a diameter of 1/10000 of a millimeter (Card et al., 26).The envelope is composed of lipid, and it is acquired from the host cell of plasma membrane. The viral genes are surrounded by an icosahedral or conical capsid which is composed viral proteins. Social scientist, Dr, Card explained that the bullet shaped capsid surrounds two identical single stranded and positive sense RNA genome per virion. The genome RNA is converted into double stranded DNA using reverse transcriptase. This genome of RNA encodes for three structural genes (gag, pol, and env) and six regulatory proteins (tat, rev, vif, vpr, and vpu) respectively. The information contained in structural genes are used to make structural proteins for new viruses. For example, structural gene of env encodes envelope protein called gp160, which is broken down by a viral enzyme to form gp 120 and gp 41. These two glycoprotein gp120 and gp41 play a major role in the viral replication cycle during attachment and exiting the cell (Card et al., 28). Dr. Card explained that membrane associated matrix and capsid protein, and also enzymes such as reverse transcriptase, Rnase H and integrase are encoded by gene gag. The six regulatory genes encodes for protein that control the information needed to infect a target cell. For instance, nef gene encodes protein that is necessary for the virus to replicate, and the vpu encodes protein that promotes the new virus to bud off from the infected cell.

The main target of HIV is the infected person immune system. The immune system function based on the white blood cell known as lymphocytes to defend the body against foreign substance (poindexter, 8). The two types of lymphocytes called B and T lymphocytes circulate in the blood and lymphatic fluids. When the foreign particles enter into the body, the B lymphocyte generates antibodies to bind with the foreign particles. This binding allows other cells of the immune system to attack the foreign particle. Based on professor Poindexter, the T-cells are responsible for cell- mediated immunity which plays role in identifying the infected body and alert the immune system for attack (Poindexter, 8). HIV uses a CD4 or also knows as a helper cell as a receptor. The helper cells are subtype of T-cell that stimulates the immune response when the antigen binds to its surface called CD4 cells.

A member of retroviruses such as HIV has a unique replication cycle and function. The first step is the attachment in which the virus protein gp120 binds to the CD4+ receptors. A social worker, Dr. Card explained that during attachment the co-receptors CCR5 and CXC4 provide conformational change in gp120 by promoting further binding with the CD4+ cells. This confirmation allows viral gp41 to unfold and insert its hydrophobic terminus into the host cell membrane. When the gp41 folds back into the cell, it allows the virus to pull down to the cell and diffuse its membrane. Once the virus enters into the cell, it uncoated the capsid and release two RNA strands and three very important enzymes known as reverse transcriptase, integrease, and protease (Card et al., 28). There are two important domain found in reverse transcriptase. These are ribonuclease H active site and the polymerase active site. The single stranded RNA is transcribed to RNA-DNA double helix in the polymerase active site. Then the ribonuclease H-active site finishes the remaining DNA strand by forming double stranded DNA helix (Card et al., 28). After the transcription step the virus uses integrase which cleaves dineucleotide from each 3' end of the DNA and creates two sticky ends. Based on Dr, Card description, this viral dsDNA transfer into the nucleus and integrate it with the host genome. This is the most important step for the virus because; it can replicate itself using the host DNA as a factory. The host cell transcribes the viral DNA into mRNA which travels into the cytoplasm where building blocks of viral protein are synthesized. The next crucial step is done by protease which cleaves longer protein into smaller core protein. At this point the viral RNA strands and replication enzymes assemble around the core protein forming the capsid (Card et al., 29). This immature virus is not infectious, however when the virus leaves the cell it gets its envelope from the host and viral proteins and become mature and ready to infect other cells. The virus infection progress in three different stages which are primary or acute infection, asymptomatic and symptomatic disease progression (AIDS).

Acute infection is the first stage of HIV disease. When the virus first enters the body it infects the CD4 cells and replicate in the lymph nodes with in two or three days. Study shows that 87% of infected persons develop flu-like symptoms within two to four weeks (Poindexter, 9). The symptoms occur in this stage are a high fever, joint and muscle pain, chills, headaches, night sweats, rashes, and swollen glands (Poindexter, 10). During this stage, the infected person is highly infectious because there is a high amount of HIV present in the genital fluids (Card et al., 31) However, majority of infected people do not realize they are infected with HIV. The reason behind for this is the immune system does not produce antibodies to fight the virus as soon as the virus enters the body. According to Poindexter study, the immune system produces antibodies after 6-12 weeks of infection. Therefore if a person takes HIV test before the antibodies are produced by the immune system, it is most likely possible to get a false negative result.

The next stage the HIV+ person is going to enter is asymptomatic period. At this stage the infected person sheds the virus, and there are no signs or symptoms of HIV infection. For this reason, this period is also called clinical latency (Card et al., 31). The period of time the person shows symptoms varies between individual based on their overall health and immune system functioning. Based on Card study, the average time of latency is 7 to 8 years. However, now showing symptoms during this period does not mean the person is healthy. During this stage the virus is actively multiplying, infecting and killing the immune system cells slowly (Card et al., 31). During this period the number of CD4+ cells starts to decline over time. Due to the decreasing number of CD4+ cells, the infected person may shows some mild symptoms such as swollen lymph nodes, fatigue, weight loss, frequent fever and sweats and also frequent or persistent yeast infections (Card et al., 45)

The last stage called symptomatic period, HIV+ people experience more sever symptoms which include opportunistic infections and diseases (Poindexter, 10). At this stage the virus multiplies rapidly and large quantities of the virus enter the bloodstream. Due to this reason there are no enough healthy CD4+ cells to defend the body against the virus. Therefore HIV+ people start to develop opportunistic infections and become an AIDS patient. Opportunistic infections are diseases that are caused by bacteria, funguses or viruses. According to Poindexter explanation, opportunistic infections do not cause diseases to people with healthy immune system, however it can cause sever diseases to HIV+ people with a CD4+ cell count of less than 200 (Poindexter, 10). People who become an AIDS patient develop symptoms includes Pneumonia, Kaposi’s Sacroma (a kind of cancer), HIV wasting syndrome (extreme weight loss), HIV encephalopathy (AIDS dementia) and yeast infections of the trachea, bronchi and esophagus.

Today there is no adequate treatment exists for eradication of the AIDS virus from those already infected with HIV. However, several antiretroviral drugs are available to keep the amount of HIV in the body at a low level. It is very challenging to make effective drugs that cure AIDS disease. This is because viruses belong to retroviruses mutates quickly; therefore there is a high chance to become resistant to the drug. For this reason, HAART (Highly Active Antiretroviral Therapy) is recommended by Doctors which require taking a combination of three or more antiretroviral drug (Card et al., 9). The drugs are mainly target to inhibit viral enzyme activity. According to researcher Poindexter, The most frequent prescribed treatments are grouped into three classes which are nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs) (Poindexter, 18). For example, NRTIs treatment based drugs are specifically produce to block the enzyme reverse transcriptase from transcribing the single RNA stranded genome of the virus into DNA strand. Therefore the next step of viral replication can be prevented. Some examples of brand names of NRTIs include Retrovir, Epivir and Emtriva. The use of antiretroviral drugs has dramatically reduced the HIV transmission from mother to baby vertically. According to Poindexter, there is a 20% to 30% chance of transmitting HIV from mother to baby without treatment. However, if pregnant women take antiretroviral drugs during pregnancy, performs a cesarean sections during delivery and provide medication to the new born, there will be less than 2% vertical HIV transmission (Poindexter, 18). There are several side effects come along with this drug such as abdominal pain, nausea and diarrhea. Professor Poindexter also describes the other anti-HIV treatment called Protease inhibitors (PIs) target the inhibition of viral enzyme called protease. Protease enzyme works at a later stage of viral cycle where it cleaves the viral protein to become mature enough to infect other cells. Therefore inhibiting this enzyme will make the virus non infectious. Some brand names of PIs include Aptivus, Novir and Viracept. This drug also causes side effects such as diarrhea, nausea, digestive tract disorder, and also increases triglyceride levels which lead to diabetes (Poindexter, 19)

Despite the availability of drugs, there is an increasing population of HIV infected persons in Ethiopia. The reason behind this is that the limited access to the drugs due to its cost. In July 2003, the Ethiopia government introduces fee-based antiretroviral therapy. According to World Health fact sheet, individuals infected with HIV-1 are required to pay for their own HIV medication at a cost of US$28.00 which is an equal amount of $280.00birr (Ethiopian money). However, not only the cost of the drug is the reason for an increasing population of HIV infected persons. The lack of education about the effect of the drug is also plays a major role in HIV epidemic. The complex dosing schedules, drug interactions and toxicities along with drug compliance for taking life long is still a big challenge for taking the medications properly. There is no vaccine developed for HIV virus still now. The main strategy prevention of HIV/AIDS is using standard precautions including blood screening, not sharing sharp objects, standard precaution in using needle, safe sex and prevention of mother to child transmission.

AIDS is now recognized as the leading cause of adult morbidity and mortality in Ethiopia. According to World Health Organization report, there are several factors that speed up the impact of HIV epidemic such as poverty, food shortages, and socio-economic status. According to the data made by UNAIDS and the World Health Organization (WHO), from the total population of Ethiopia which is 88 million, it is estimated that 980,000 people are living with HIV/AIDS and 67,000 people died from the virus. Heterosexual contact is one of the major transmissions of HIV among young adults. Luck of knowledge about understanding the different rout of HIV transmission and preventing methods promote HIV epidemics in Ethiopia. Based on the data analysis, the prevalence of HIV/AIDS is higher among women (2.6%) compares to men (1.8%). The data also indicates, women who are sex workers are the most at risk by covering 25.3% of the total population living with HIV/AIDS. The main reasons that increase the vulnerability of HIV among women poverty, luck of access to education and also physical and sexual abuses by partners. According to the fact sheet of World Health Organization, 29% of people who live with HIV/AIDS received antiretroviral drug therapy. Among this people, only 8% HIV+ pregnant women received antiretroviral drug. This indicates there is a high risk of getting HIV+ new born babies through vertical transmission. Based on UNAIDS report, in 2009 approximately 72,945 children under the age of 15 were living with HIV. It is very common to see children who lost their parents with AIDS live under extreme emotional and physical stress. According to the UNAID report, among the total population 855,720 children under the age of 18 had lost at least one parent with AIDS. These children are forced to live on the street due to discrimination by the society.

HIV has greatly affects and costs so many lives in underdeveloped nations of sub-Saharan Africa. It has been the most challenging task for medical professional to find a cure for HIV/AIDS due to its rapid mutating behavior. HIV is very unique compares to other retroviral viruses. The bullet shaped capisd surrounds two identical single stranded RNA and enzymes such as transcriptase, protease, and integrase which are essential for the replication of virus. Without these three essential enzymes the steps of viral replication will be unsuccessful. Therefore most antiretroviral drugs are developed to inhibit the viral enzymatic activities such as NRT’s and PIs. However these retroviral drugs only work in minimizing the level of HIV in the body. A complete cure of HIV is not ye discovered. The HIV infection has three stages which are acute, asymptomatic and symptomatic or latent. In these three stages the virus progresses throughout time. In all three stages the infected person is contagious to other people. Despite the discovery of antiretroviral, HIV is still critical public health concern in Ethiopia. According to USAIDS report women are the most at risk of getting HIV compares to men. Based on the USAIDS data, children are also the main victim of HIV infection in Ethiopia due to vertical transmission route. The lack of knowledge about prevention and treatment is the main factor for the epidemic of HIV in Ethiopia.

Work Cited

Card, J., Amarillas, A.,Conner, A., Akers,D.,Solomon,J.,Diclemente,R. The completeHIV/AIDS Teaching Kit. Newyork: Springer publishing company, 2007. 8-45. Print.

"Countries offering free access to HIV treatment." world health organization fact sheet, 2005. Web. 4

Nov. 201. <>.

"HIV/AIDS HEALTH PROFILE." USAIDS ETHIOPIA from the american people, 2010. Web. 4 Nov. 2010. <>.

Poindexter, cynthia c. Hand book of HIV and social work. New Jersey: john wiley & sons inc, 2010. 7-18.