HIV transmission and epidemiology US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for HIV transmission and epidemiology. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
HIV transmission and epidemiology US Medical PG Question 1: A 2300-g (5-lb 1-oz) male newborn is delivered to a 29-year-old primigravid woman. The mother has HIV and received triple antiretroviral therapy during pregnancy. Her HIV viral load was 678 copies/mL 1 week prior to delivery. Labor was uncomplicated. Apgar scores are 7 and 8 at 1 and 5 minutes respectively. Physical examination of the newborn shows no abnormalities. Which of the following is the most appropriate next step in management of this infant?
- A. Administer lamivudine and nevirapine
- B. Administer zidovudine, lamivudine and nevirapine (Correct Answer)
- C. Administer nevirapine
- D. Administer zidovudine
- E. HIV antibody testing
HIV transmission and epidemiology Explanation: ***Administer zidovudine, lamivudine and nevirapine***
- The mother has a **viral load of 678 copies/mL**, which falls into the **intermediate-risk category** (50-999 copies/mL) for HIV transmission.
- Current guidelines recommend **combination antiretroviral prophylaxis** (zidovudine + lamivudine + nevirapine) for infants born to mothers with viral loads in this range, typically given for 2 weeks followed by zidovudine alone to complete 4-6 weeks.
- This enhanced regimen provides better protection than monotherapy when maternal viral suppression is suboptimal.
*Administer zidovudine*
- Zidovudine monotherapy is reserved for **low-risk infants** whose mothers have viral loads **<50 copies/mL** at delivery with documented adherence to ART during pregnancy.
- With a maternal viral load of 678 copies/mL, monotherapy alone is **insufficient** and would not meet current standard of care for HIV prophylaxis.
*Administer lamivudine and nevirapine*
- This regimen omits **zidovudine**, which remains the **backbone of neonatal HIV prophylaxis** and should always be included.
- Using only lamivudine and nevirapine without zidovudine is not consistent with established guidelines.
*Administer nevirapine*
- Nevirapine monotherapy is **not adequate** for HIV prophylaxis in developed countries with access to combination therapy.
- While nevirapine may be used as a single dose in resource-limited settings, it should be part of a multi-drug regimen when other agents are available.
*HIV antibody testing*
- HIV antibody testing in newborns will detect **maternal antibodies** that crossed the placenta and cannot determine the infant's true infection status at birth.
- While HIV diagnostic testing using **PCR or viral load assays** will be performed at 14-21 days, 1-2 months, and 4-6 months of age, **antiretroviral prophylaxis must be initiated immediately** after birth to prevent transmission.
HIV transmission and epidemiology US Medical PG Question 2: A research group designed a study to investigate the epidemiology of syphilis in the United States. The investigators examined per capita income and rates of syphilis in New York City, Los Angeles, Chicago, and Houston. Data on city-wide syphilis rates was provided by each city's health agency. The investigators ultimately found that the number of new cases of syphilis was higher in low-income neighborhoods. This study is best described as which of the following?
- A. Double-blind clinical trial
- B. Prospective cohort study
- C. Case-control study
- D. Case series
- E. Ecological study (Correct Answer)
HIV transmission and epidemiology Explanation: ***Ecological study***
- This study design examines the relationship between **exposure** (per capita income) and **outcome** (syphilis rates) at the **population level** (cities, neighborhoods) rather than at the individual level.
- It uses **aggregate data** from health agencies to identify patterns and correlations, which is characteristic of an ecological study.
*Double-blind clinical trial*
- A double-blind clinical trial is a type of **interventional study** where neither the participants nor the researchers know who is receiving the treatment versus placebo.
- This study is **observational** and does not involve any intervention or blinding.
*Prospective cohort study*
- A prospective cohort study follows **individuals over time** to see who develops a disease based on their exposure status.
- This study does not follow individuals; instead, it looks at **population-level data** at a single point or period.
*Case-control study*
- A case-control study compares individuals with a disease (**cases**) to individuals without the disease (**controls**) and retrospectively looks for differences in their past exposures.
- This study does not identify individual cases and controls or look back at individual exposures.
*Case series*
- A case series describes the characteristics of a group of patients with a particular disease or exposure.
- This study analyzes **population-level income and disease rates**, not detailed clinical information on individual cases.
HIV transmission and epidemiology US Medical PG Question 3: A 27-year-old G2P1 woman is diagnosed with an HIV infection after undergoing routine prenatal blood work testing. Her estimated gestational age by first-trimester ultrasound is 12 weeks. Her CD4 count is 150 cells/mm^3 and her viral load is 126,000 copies/mL. She denies experiencing any symptoms of HIV infection. Which of the following is appropriate management of this patient's pregnancy?
- A. HAART (Correct Answer)
- B. Breastfeeding
- C. Vaginal delivery
- D. HAART after delivery
- E. Avoidance of antibiotic prophylaxis
HIV transmission and epidemiology Explanation: ***HAART***
- **Highly active antiretroviral therapy (HAART)** is recommended immediately for pregnant women with HIV, regardless of CD4 count or viral load, to reduce maternofetal transmission.
- Starting HAART early in pregnancy significantly lowers the **viral load**, protecting the fetus from HIV infection.
*Breastfeeding*
- **Breastfeeding** is contraindicated in HIV-positive mothers in developed countries because it carries a risk of HIV transmission to the infant.
- Formula feeding is recommended to prevent **postnatal HIV transmission**.
*Vaginal delivery*
- A **vaginal delivery** may be considered if the viral load is undetectable or very low (<1,000 copies/mL) at the time of delivery.
- Given this patient's **high viral load** (126,000 copies/mL), a scheduled cesarean section would be indicated to minimize the risk of perinatal transmission.
*HAART after delivery*
- Delaying **HAART until after delivery** would increase the risk of maternofetal HIV transmission during pregnancy and delivery.
- Prompt initiation of HAART is crucial for both maternal health and **fetal protection**.
*Avoidance of antibiotic prophylaxis*
- **Antibiotic prophylaxis** is commonly used in combination with antiretroviral agents to prevent opportunistic infections, especially when the **CD4 count is low** (<200 cells/mm³).
- Given a CD4 count of 150 cells/mm³, prophylaxis against opportunistic infections like **Pneumocystis jirovecii pneumonia** might be indicated, making avoidance inappropriate.
HIV transmission and epidemiology US Medical PG Question 4: A 17-year-old girl comes to the urgent care center after testing negative for HIV. She recently had sexual intercourse for the first time and had used a condom with her long-term boyfriend. She has no personal history of serious illness and no history of sexually transmitted infections. However, the patient is still worried about the possibility she has HIV despite the negative HIV test. She states that the package insert of the HIV test shows that of 100 patients who are found to be HIV-positive on PCR, 91 tested positive via the HIV test. Later in the day, a 23-year-old woman with a history of genitourinary chlamydia infection also comes to the urgent care center after testing negative for HIV. She states that she recently had unprotected intercourse with “someone who might have HIV.” If the test is conducted a second time on the 23-year-old patient, how will its performance compare to a second test conducted on the 17-year-old patient?
- A. Decreased positive predictive value
- B. Increased validity
- C. Increased sensitivity
- D. Decreased negative predictive value (Correct Answer)
- E. Increased specificity
HIV transmission and epidemiology Explanation: ***Decreased negative predictive value***
- The 23-year-old patient has a higher **pre-test probability** of HIV due to unprotected intercourse with a high-risk partner and a history of STIs, which increases the likelihood of HIV exposure and acquisition.
- A higher pre-test probability for a disease will **decrease the negative predictive value** of a test while increasing its positive predictive value, even if the test's sensitivity and specificity remain constant.
*Decreased positive predictive value*
- A higher **pre-test probability** (like in the 23-year-old patient) actually **increases the positive predictive value** of a diagnostic test, given the same sensitivity and specificity.
- The positive predictive value reflects the probability that a positive test result correctly identifies someone with the disease.
*Increased validity*
- **Validity** refers to how well a test measures what it is supposed to measure (accuracy), and it is not expected to change based on the individual patient's risk factors.
- The intrinsic properties of the test (sensitivity and specificity) determine its validity, not the prevalence of the disease or the patient's pre-test probability.
*Increased sensitivity*
- **Sensitivity** is a fixed characteristic of the test itself, defined as the proportion of true positives correctly identified by the test.
- A patient's individual risk factors or pre-test probability do not alter the inherent sensitivity of the HIV test.
*Increased specificity*
- **Specificity** is also a fixed characteristic of the test, representing the proportion of true negatives correctly identified.
- The test's specificity does not change based on the prevalence of HIV in the population or the patient's individual risk for the disease.
HIV transmission and epidemiology US Medical PG Question 5: A 29-year-old woman tests positive for HIV during pregnancy screening. She is concerned about transmission to her baby. Which of the following interventions most significantly reduces the risk of vertical transmission?
- A. Avoiding breastfeeding only
- B. Cesarean delivery only
- C. Antiretroviral therapy during pregnancy and labor (Correct Answer)
- D. Maternal immunization
HIV transmission and epidemiology Explanation: ***Antiretroviral therapy during pregnancy and labor***
- **Antiretroviral therapy (ART)** significantly reduces the **viral load** in the mother, thereby minimizing the risk of HIV transmission to the fetus during pregnancy and childbirth.
- When combined with other strategies like **cesarean section** and **avoidance of breastfeeding** in developed countries, ART can reduce vertical transmission rates to less than 1%.
*Avoiding breastfeeding only*
- While **avoiding breastfeeding** is a crucial intervention, especially in settings where safe alternatives are available, it addresses only one mode of transmission (postnatal).
- It does not prevent **in-utero** or **intrapartum transmission**, which are primary routes of vertical transmission if the viral load is high.
*Cesarean delivery only*
- **Cesarean delivery** can reduce the risk of transmission by avoiding exposure to maternal blood and secretions during vaginal delivery.
- However, it is most effective when the maternal **viral load is high** and is often combined with ART for maximum efficacy; it's less effective without ART.
*Maternal immunization*
- **Maternal immunization** involves administering vaccines to the mother to protect against specific infections, primarily bacterial or viral diseases like influenza or tetanus.
- It has **no direct impact** on the risk of HIV transmission, as there is currently no vaccine available for HIV.
HIV transmission and epidemiology US Medical PG Question 6: A 24-year-old newly immigrated mother arrives to the clinic to discuss breastfeeding options for her newborn child. Her medical history is unclear as she has recently arrived from Sub-Saharan Africa. You tell her that unfortunately she will not be able to breastfeed until further testing is performed. Which of the following infections is an absolute contraindication to breastfeeding?
- A. Human Immunodeficiency Virus (HIV) (Correct Answer)
- B. Latent tuberculosis
- C. Hepatitis B
- D. Hepatitis C
- E. All of the options
HIV transmission and epidemiology Explanation: ***Human Immunodeficiency Virus (HIV)***
- In developed countries where safe alternatives are available, **HIV-positive mothers** are advised against breastfeeding due to the risk of **vertical transmission** through breast milk.
- This is considered an **absolute contraindication** in settings where formula feeding is accessible and safe.
*Latent tuberculosis*
- **Latent tuberculosis** is not a contraindication to breastfeeding; mothers can breastfeed while receiving treatment.
- Active, untreated tuberculosis, however, generally requires temporary separation of mother and child until the mother is no longer infectious, but pumping and feeding expressed milk is often still an option.
*Hepatitis B*
- **Hepatitis B** infection in the mother is not a contraindication to breastfeeding, especially if the infant receives **hepatitis B vaccine** and **Hepatitis B Immune Globulin (HBIG)** at birth.
- Breastfeeding is considered safe and does not increase the risk of transmission to the infant.
*Hepatitis C*
- **Hepatitis C** is generally **not a contraindication** to breastfeeding, as studies have shown a very low risk of transmission through breast milk.
- Breastfeeding is supported unless the mother has **cracked or bleeding nipples**, which could potentially allow viral transmission.
*All of the options*
- This option is incorrect because **only HIV** is considered an absolute contraindication to breastfeeding in settings where safe alternatives are available.
- Latent TB, Hepatitis B, and Hepatitis C alone do not preclude breastfeeding.
HIV transmission and epidemiology US Medical PG Question 7: A 28-year-old woman G1P0 presents at 38 weeks of gestation for a standard prenatal visit. She endorses occasional mild lower back pain but otherwise remains asymptomatic. Her past medical history is significant for HIV for which she is treated with azidothymidine (AZT). Her vital signs and physical exam are unremarkable. Her current HIV viral titer level is 1,400 copies. If she were to go into labor today, what would be the next and most important step for the prevention of vertical HIV transmission to the newborn?
- A. Urge the patient to have a cesarean section delivery (Correct Answer)
- B. Add nevirapine to the patient’s AZT
- C. Treat the newborn with AZT following delivery
- D. Increase AZT dose
- E. Avoid breastfeeding
HIV transmission and epidemiology Explanation: ***Urge the patient to have a cesarean section delivery***
- A **high viral load** (>1000 copies/mL) at 38 weeks gestation is an indication for a **scheduled cesarean section** to reduce the risk of vertical HIV transmission.
- This approach minimizes the infant's exposure to maternal blood and genital secretions during vaginal delivery.
*Add nevirapine to the patient’s AZT*
- While adding a second antiretroviral (ARV) medication is generally beneficial in HIV treatment, a single dose of **nevirapine** given to the mother in labor is typically used when **highly active antiretroviral therapy (HAART)** has not been given prenatally or with unknown viral load status.
- The primary intervention for a known high viral load near term is delivery mode modification.
*Treat the newborn with AZT following delivery*
- This is a standard and essential component of **post-exposure prophylaxis (PEP)** for all infants born to HIV-positive mothers, regardless of maternal viral load or delivery route.
- However, it is a post-delivery intervention and not the **next and most important step** for prevention *at the time of labor* with a high viral load.
*Increase AZT dose*
- Increasing the dose of a single ARV medication like **AZT** alone is unlikely to rapidly suppress a viral load of 1,400 copies/mL sufficiently to mitigate transmission risks during labor, and could lead to toxicity.
- Achieving viral suppression before labor is crucial, and if not achieved, a C-section is indicated.
*Avoid breastfeeding*
- **Avoiding breastfeeding** is a critical recommendation for HIV-positive mothers in developed countries to prevent **postnatal vertical transmission**.
- While important for overall prevention, it addresses transmission after birth and is not the immediate and most important step to prevent transmission *at the onset of labor* when a high viral load is present.
HIV transmission and epidemiology US Medical PG Question 8: A 28-year-old G1P0 woman at 16 weeks estimated gestational age presents for prenatal care. Routine prenatal screening tests are performed and reveal a positive HIV antibody test. The patient is extremely concerned about the possible transmission of HIV to her baby and wants to have the baby tested as soon as possible after delivery. Which of the following would be the most appropriate diagnostic test to address this patient’s concern?
- A. CD4+ T cell count
- B. Viral culture
- C. Polymerase chain reaction (PCR) for HIV RNA (Correct Answer)
- D. Antigen assay for p24
- E. EIA for HIV antibody
HIV transmission and epidemiology Explanation: ***Polymerase chain reaction (PCR) for HIV RNA***
- **PCR for HIV RNA** directly detects the viral genetic material, providing a definitive diagnosis of HIV infection in an infant.
- Unlike antibody tests, PCR can distinguish between passively acquired maternal antibodies and actual infant infection, making it suitable for newborns.
*CD4+ T cell count*
- **CD4+ T cell count** is used to monitor the progression of HIV infection and immunosuppression, not for initial diagnosis, especially in neonates.
- While it's an important marker for HIV disease, it does not confirm the presence of the virus itself in a newborn.
*Viral culture*
- **Viral culture** is a highly specific method for detecting HIV, but it is expensive, time-consuming, and technically demanding.
- It is not routinely used for rapid early diagnosis in neonates due to its practical limitations and the availability of faster, reliable alternatives like PCR.
*Antigen assay for p24*
- The **p24 antigen test** can detect early HIV infection in adults, but its sensitivity is lower in neonates compared to PCR, especially immediately after birth.
- It may not reliably detect infection in newborns due to low viral loads or the presence of maternal antibodies that complex the antigen.
*EIA for HIV antibody*
- An **EIA for HIV antibody** will detect maternal antibodies that have crossed the placenta, meaning it will be positive in nearly all infants born to HIV-positive mothers, regardless of the infant's infection status.
- This test cannot distinguish between passive maternal antibody transfer and true infant infection.
HIV transmission and epidemiology US Medical PG Question 9: A 27-year-old pregnant woman presents to an obstetrician at 35 weeks gestation reporting that she noted the presence of a mucus plug in her vaginal discharge this morning. The obstetrician performs an examination and confirms that she is in labor. She was diagnosed with HIV infection 1 year ago. Her current antiretroviral therapy includes abacavir, lamivudine, and nevirapine. Her last HIV RNA level was 2,000 copies/mL 3 weeks ago. Which of the following anti-retroviral drugs should be administered intravenously to the woman during labor?
- A. Enfuvirtide
- B. Nevirapine
- C. Abacavir
- D. Rilpivirine
- E. Zidovudine (Correct Answer)
HIV transmission and epidemiology Explanation: ***Zidovudine***
- Intravenous **zidovudine** is recommended during labor for HIV-positive pregnant women, especially when the viral load is **>1000 copies/mL**, to reduce the risk of **mother-to-child transmission (MTCT)**.
- This intervention significantly lowers the viral load in the maternal blood and reduces fetal exposure to the virus during delivery.
*Enfuvirtide*
- **Enfuvirtide** is a **fusion inhibitor** administered subcutaneously, not intravenously, and is reserved for treatment-experienced patients with multi-drug resistant HIV.
- It is not a standard recommendation for intrapartum prophylaxis against MTCT.
*Nevirapine*
- **Nevirapine** is an **NNRTI** that is typically given orally, and while it has been used for MTCT prophylaxis, intravenous administration is not standard for intrapartum use.
- The woman is already on oral nevirapine as part of her ART regimen.
*Abacavir*
- **Abacavir** is an **NRTI** given orally and is part of the patient's current ART regimen.
- It is not administered intravenously for intrapartum MTCT prophylaxis.
*Rilpivirine*
- **Rilpivirine** is an **NNRTI** that is taken orally and is not indicated for intravenous administration during labor to prevent MTCT.
- Its use is limited by potential drug interactions and efficacy in patients with high viral loads.
HIV transmission and epidemiology US Medical PG Question 10: A 39-year-old man presents with a 4-week history of painless, non-discharging lesions on his penis and scrotum. He was diagnosed with chronic myeloid leukemia two years ago and treated with imatinib. He currently takes no medications. He has a 20-pack-year smoking history and drinks 1-2 beers on weekends. He reports unprotected intercourse with a woman while traveling abroad 4 months ago. His temperature is 37°C, pulse is 85/min, and blood pressure is 128/82 mm Hg. Examination reveals three non-tender lesions, each approximately 1 cm in size, on his genitalia. There is no inguinal lymphadenopathy. Which of the following is the most likely causative organism?
- A. Haemophilus ducreyi
- B. Chlamydia trachomatis
- C. Treponema pallidum (Correct Answer)
- D. Herpes simplex virus
- E. Klebsiella granulomatis
HIV transmission and epidemiology Explanation: ***Treponema pallidum***
- The presentation of **painless, non-discharging genital lesions** (chancre) after unprotected intercourse 4 months prior is highly characteristic of **primary syphilis**, caused by *Treponema pallidum*.
- The absence of **inguinal lymphadenopathy** is not uncommon in early primary syphilis, and the patient's history of travel and unprotected sex increases the risk.
*Haemophilus ducreyi*
- This bacterium causes **chancroid**, which typically presents as **painful genital ulcers** with irregular borders and often significant **inguinal lymphadenopathy** (buboes).
- The patient's lesions are described as painless, ruling out chancroid.
*Chlamydia trachomatis*
- While certain serovars of *Chlamydia trachomatis* cause **lymphogranuloma venereum (LGV)**, initial lesions are usually small, transient, and often go unnoticed, followed by prominent and often painful **inguinal lymphadenopathy**.
- Other serovars cause nongonococcal urethritis or cervicitis, which do not typically present with the described painless ulcers.
*Herpes simplex virus*
- **Herpes simplex virus (HSV)** infection usually causes **painful, vesicular lesions** that can ulcerate and crust, often accompanied by prodromal symptoms like itching or tingling.
- The lesions in this case are described as painless and non-vesicular.
*Klebsiella granulomatis*
- This organism causes **granuloma inguinale (donovanosis)**, which is characterized by **painless, beefy-red, friable ulcers** that can be extensive and bleed easily.
- While painless, the description of "non-discharging lesions" and the typical appearance of syphilis differ from the classic "beefy red" appearance of donovanosis.
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