Question
A male patient aged 35 years came to STD outpatient department with a history of exposure and is complaining of intractable diarrhea of one month duration with loss of weight and prolonged fever. Answer the following:
- (a) Mention the probable diagnosis 1 mark(s)
- (b) Describe the morphology of the virus causing the disease 2 mark(s)
- (c) How will you proceed with laboratory diagnosis in this case 3 mark(s)
- (d) Discuss the other modes of transmission 2 mark(s)
- (e) How the disease can be prevented 2 mark(s)
Answer
a) Probable diagnosis: AIDS (HIV infection) — intractable chronic diarrhoea, weight loss, and prolonged fever in a patient with a relevant STD-clinic exposure history is classical of advanced HIV disease.
b) Morphology of HIV HIV is a spherical, enveloped retrovirus (family Retroviridae, genus Lentivirus), approximately 100–120 nm in diameter. The outer lipid envelope (derived from the host cell membrane) is studded with glycoprotein spikes — gp120 (outer, mediates CD4 receptor binding) and gp41 (transmembrane, mediates membrane fusion). Beneath the envelope lies the matrix protein (p17). The conical capsid (core), formed by p24 protein, encloses two copies of single-stranded, positive-sense RNA genome, along with the essential viral enzymes reverse transcriptase, integrase, and protease, required for the retroviral replication cycle.
c) Laboratory diagnosis
- Screening: ELISA for HIV antibody (4th-generation assays also detect p24 antigen, narrowing the window period).
- Rapid tests: point-of-care immunochromatographic rapid antibody tests.
- Confirmatory test: Western blot (detects antibody against specific viral proteins — gp41, gp120/160, p24) or a supplemental testing algorithm per national guidelines.
- CD4 count: flow cytometry, to assess degree of immunosuppression and guide staging/prophylaxis.
- Viral load: quantitative HIV RNA PCR, for monitoring disease progression and antiretroviral treatment response.
d) Other modes of transmission Besides sexual contact (the predominant route in this patient’s exposure history), HIV is transmitted parenterally (blood/blood products, contaminated needles/injecting drug use, needle-stick injury) and via vertical/perinatal transmission (mother-to-child — in utero, during delivery, or via breastfeeding).
e) Prevention Safe sexual practices (condom use, partner reduction); screening of blood/blood products before transfusion; safe injection practices and needle-exchange programmes for people who inject drugs; prevention of mother-to-child transmission (antiretroviral therapy during pregnancy/delivery/breastfeeding, avoiding breastfeeding where safe alternatives exist); post-exposure prophylaxis after high-risk exposure; pre-exposure prophylaxis (PrEP) for high-risk individuals; and health education/awareness programmes.