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Human Immunodeficiency virus Human Immunodeficiency Virus (HIV) is the causes of AIDS. HIV has a tendency to infect and attack the CD4 cells (T helper cells)that are important to modulate the immune system. Hence infection with this virus suppress the immune system. As a consequence, these patients will be affected from not only from virulent pathogens but also from opportunistic pathogens that does not cause serious disease in Immunocompetent persons. Furthermore the immune system is important to control replication of abnormal cells like cancerous cells, but in HIV infected individuals, this control mechanism is not fully functional and there is a high tendency to develop malignant disorders. In the last decade, Infection with HIV has become the number one causes of mortality in some of the Sub-Sahara Africa countries.
Transmission
Incubation period The immunological window period is between 6 weeks to 3 months. The immunological widow period is the time between infection and the time when the antibody level become detectable by ELISA or EIA. Some patients may develop some symptoms during primary infection. In the first three months of infection, patients may present with a condition known as AIDS associated illness. On the contrary a few patients do not develop any clinical problems for more than 12 years. Once infection occur, eradication of the virus is not possible even with the potent Highly Active AntiRetroviral Therapy (HAART) regimen.
Clinical presentations
Seroconversion illness (primary infection) Ø Fever. Ø Skin rash Ø Mild generalised lymphadenopathy Ø Mild aseptic meningitis.
Progressive Generalized lymphadenopathy Ø Lymphadenopathy in more than one site (other than inguinal region)
Symptomatic patients Ø Lympadenopathy Ø Shingles Ø Pneumococcal pneumonia Ø Candidacies
AIDS defining illness ü Opportunistic infections ü Opportunistic malignancy ü Constitutional symptoms ü Diarrhoea for more than 1 month ü Weight loss over 10 % in 6 months ü Night sweet
Investigation
Diagnostic tests
Symptomatic patients Blood sample should be taken and send to the virology lab.There should be at least two positive results to diagnose HIV infection. The two tests should be different in the methods or quality of the antigen they use. HIV antibody negative results will exclude HIV infection.
Seroconversion illness samples
Serum from patient with seroconversion illness may occasionally give a false negative result but if the test is repeated after 5-7 days there is a high chance to demonstrate seroconversion. Molecular tests is useful. HIV Proviral DNA PCR is very sensitive. (HIV RNA PCR test used for monitoring viral load is not validated for this purpose).
Recent exposure Patient with recent exposure should have serological and molecular tests. Serum for HIV antibody and Blood in EDTA for HIV Proviral DNA at 6,12 and 24 weeks of exposure should be send to virology or microbiology laboratory.
Infants and neonates In infants- Blood in EDTA for HIV proviral DNA or HIV RNA PCR. Or Serum for P24 in setting where there is no facility for molecular test. - In infants absence of antibody after 6 months may exclude HIV infection.
In countries with limited resources, P24 antigen test still can be used to supplement antibody test.
Appropriate test for Infants and children (PDF)
Treatment
Treatment with antiviral- Highly Active AntiRetroviral Therapy (HAART) regimen is the best treatment option. Triple drugs are used to treat patients. Two NRTIs, and one NNRTI or PI are used in combination. Viral load and CD4 cell count is used to monitor response to therapy. At present viral load is done every 3 month while on therapy. Tests that may be used to identify adverse side effects. They should be done before starting therapy and at least every 3 months. Ø Full blood count Ø Glucose and cholesterol level. Ø Liver and renal function tests should be carried out regularly.
Patients who does not responds to therapy should be tested for resistance. Response can be defined as a decline in Viral load or an increase in CD 4 cell counts. Clinical response can be defined as a positive progress in the patient conditions and wellbeing.
Indications for starting antiretroviral therapy Ø Patients presenting with AIDS defining illness or Ø Patients with CD 4 cell counts below 200 cell /ml Patients presenting with seroconversion illness or patients with CD4 counts between 200 and 350 may benefit from HAART. All pregnant women should be offered screening test for HIV and if they found to be positive prophylaxis therapy should be started during the second trimester to reduce the rate of vertical transmission.
Indication for prophylaxis for opportunistic infection ü CD4 cell counts below 50- ?? CMV prophylaxis (Gancyclovir) ü CD4 cell counts below 100- Prophylaxis for Mycobacterium Avium Complex ü CD4 cell count below 200- prophylaxis for PCP.
Vaccines that are considered to be safe and useful for HIV infected individual Ø Hepatitis B vaccine Ø Pneumococcal vaccine Ø Annual influenza vaccine
HIV infected children should have MMR if they are not severely immunocompromised.
Prevention
Health education is considered to be the most important tool to prevent transmission. Screening should be carried out by all blood banks or transfusion centres. Countries with high prevalence rate should use screened blood with certain precautions as infection in some individual may not be detected as in immunological window period, and there is a significant risk of transmission. For this reason blood transfusion should be the last resort to increase the haemoglobulin level or blood volume. Caesarean section and anti-retroviral therapy has significantly made a difference in transmission of HIV from Mother to child in developed countries. Breast feeding should be avoided if possible whether it is in developing or developed countries if the mother is found to be HIV positive.
Post-exposure prophylaxis with Anti-retroviral Therapy significantly reduces transmission.
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Date this page is updated: 04/03/2007 23:13:30 www. virologynotebook.co.uk
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