Emerging and Re-emerging Infections — MCQs
Nipah virus is transmitted by
Which one of the following is an emerging viral disease?
Which of the following is the most common vector of zoonotic diseases?
Drug of choice in methicillin-resistant Staphylococcus aureus is:
Following are examples of human "dead end" diseases except -
An elderly man who had been in several military conflicts during the early 1980s and received blood transfusions for injuries recently consulted his physician for a diagnosis of cryoglobulinemia and glomerulonephritis. Additional testing revealed that he was infected with a virus transmitted through blood. Which virus was involved in this infection?
A 16-year-old girl presents with a painfully enlarged lymph node in her right axilla and low grade fever. Peripheral blood counts are within normal limits. The lymph node is biopsied, and numerous granulomas filled with neutrophils and necrotic debris are observed. Which of the following organisms could produce this disease?
Which of the following statements about Kyasanur Forest Disease is false?
After a renal transplant, what is the most common opportunistic infection?
A 25-year-old man with 3 weeks of fever presented with tricuspid valve vegetation. The patient is an intravenous drug abuser. The most common cause of endocarditis in this patient is:
Emerging and Re-emerging Infections Indian Medical PG Practice Questions and MCQs
Question 1: Nipah virus is transmitted by
- A. Pigs
- B. Cattle
- C. Fruit bats (Correct Answer)
- D. Mosquitoes
Explanation: ***Fruit bats*** - **Fruit bats**, particularly those of the *Pteropus* genus (flying foxes), are the **natural reservoir** for Nipah virus. - The virus is shed in their **urine**, **feces**, and **saliva**, which can then contaminate fruit and other food sources. *Pigs* - **Pigs** can act as **intermediate hosts** and amplify the Nipah virus, transmitting it to humans. - However, they are not the natural reservoir; they become infected by consuming contaminated plant products or interacting with infected bats. *Cattle* - While other livestock, such as **horses** and **goats**, have been shown to be susceptible to Nipah virus infection, **cattle are not typically primary transmitters** to humans. - Their role in Nipah virus epidemiology is generally considered minor compared to bats and pigs. *Mosquitoes* - Nipah virus is **not transmitted by mosquitoes** or other insect vectors. - It is primarily spread through direct contact with infected animals or their bodily fluids, or through contaminated food.
Question 2: Which one of the following is an emerging viral disease?
- A. SARS (Correct Answer)
- B. Measles
- C. Chicken pox
- D. Rabies
Explanation: ***SARS*** - **SARS (Severe Acute Respiratory Syndrome)** emerged in 2002-2003 and caused a global outbreak, making it a classic example of an **emerging viral disease**. - Emerging viral diseases are those that have recently appeared in a population or whose incidence has increased rapidly in recent times. *Measles* - Measles is an **established and re-emerging disease**, meaning it has been present for a long time but has seen resurgence due to factors like declining vaccination rates. - It is caused by the **measles virus (MeV)**, a paramyxovirus, and has been a known human pathogen for centuries. *Chicken pox* - Chickenpox, caused by the **varicella-zoster virus (VZV)**, is a common and well-known childhood disease that has been endemic for a long time. - While it can be severe, it is not considered an emerging disease as its presence and characteristics have been established for many years. *Rabies* - Rabies, caused by the **rabies virus**, is a highly fatal disease primarily transmitted through animal bites and has been recognized globally for centuries. - Although it remains a significant public health concern, it is an **ancient and well-established zoonotic disease**, not an emerging one.
Question 3: Which of the following is the most common vector of zoonotic diseases?
- A. Sand fly
- B. Ticks
- C. Mosquito (Correct Answer)
- D. Mite
Explanation: ***Mosquito*** - Mosquitoes are responsible for transmitting a vast number of **zoonotic diseases** affecting millions globally, including **malaria**, dengue, Zika, and **West Nile virus**. - Their widespread distribution and ability to feed on various hosts, including humans and animals, make them highly efficient **vectors**. *Sand fly* - Sand flies are known vectors for diseases like **leishmaniasis**, but their reach and impact are not as extensive as mosquitoes. - Leishmaniasis primarily affects specific geographic regions and isn't as globally prevalent as mosquito-borne illnesses. *Ticks* - Ticks transmit several important zoonotic diseases such as **Lyme disease**, Rocky Mountain spotted fever, and ehrlichiosis. - While significant, the global burden of tick-borne diseases is generally less than that of mosquito-borne diseases. *Mite* - Mites can transmit diseases like **scrub typhus** (via chiggers) and are associated with scabies, which is an infestation rather than a direct disease transmission. - Their role as vectors for major zoonotic diseases is comparatively limited.
Question 4: Drug of choice in methicillin-resistant Staphylococcus aureus is:
- A. Vancomycin (Correct Answer)
- B. Ampicillin
- C. Ceftriaxone
- D. Ceftazidime
Explanation: ***Vancomycin*** - **Vancomycin** is a **glycopeptide antibiotic** that kills bacteria by inhibiting peptidoglycan synthesis in the bacterial cell wall. - It is considered the **drug of choice** for serious **methicillin-resistant Staphylococcus aureus (MRSA)** infections due to its consistent activity against these resistant strains. *Ampicillin* - **Ampicillin** is a **penicillin-class antibiotic** that inhibits bacterial cell wall synthesis. - It is **ineffective against MRSA** because MRSA strains produce an **altered penicillin-binding protein (PBP2a)** that has low affinity for beta-lactam antibiotics, rendering penicillin-class drugs ineffective. *Ceftriaxone* - **Ceftriaxone** is a **third-generation cephalosporin**, which also inhibits bacterial cell wall synthesis. - Like penicillins, cephalosporins are **generally ineffective against MRSA** due to the presence of altered penicillin-binding proteins (PBP2a) in MRSA. *Ceftazidime* - **Ceftazidime** is another **third-generation cephalosporin** primarily used for its activity against **Pseudomonas aeruginosa**. - It is **not effective against MRSA**, as MRSA expresses PBP2a, rendering it resistant to most beta-lactam antibiotics, including ceftazidime.
Question 5: Following are examples of human "dead end" diseases except -
- A. Hydatid disease
- B. Japanese encephalitis
- C. Leishmaniasis
- D. Bubonic plague (Correct Answer)
Explanation: ***Bubonic plague (Plague)*** - The question refers to **plague in general**, which includes multiple clinical forms. - While **bubonic plague** (the most common form) is transmitted via **flea bites** from infected rodents and humans are typically dead-end hosts for this form, **pneumonic plague** (secondary complication or primary infection) allows **human-to-human transmission** via respiratory droplets. - This makes plague the **exception** among the listed diseases, as humans can serve as a source of infection to others in the pneumonic form, unlike true dead-end host situations. *Japanese encephalitis* - Humans are **dead-end hosts** for Japanese encephalitis virus. - Infected humans do not develop sufficient **viremia** to infect feeding mosquitoes. - The virus maintains its cycle between **Culex mosquitoes**, **pigs** (amplifying hosts), and **wading birds**, with humans being incidental hosts. *Hydatid disease* - Humans are **definitive dead-end hosts** for *Echinococcus granulosus* (causing cystic echinococcosis/hydatid disease). - The normal life cycle requires **definitive hosts** (dogs, canids) and **intermediate hosts** (sheep, cattle). - Humans develop **hydatid cysts** but cannot transmit the infection further as the parasite cannot complete its life cycle in humans. *Leishmaniasis* - In most forms of leishmaniasis, humans are considered **dead-end or accidental hosts**, particularly in **zoonotic cutaneous leishmaniasis** where animal reservoirs (rodents, dogs) maintain transmission. - However, in **anthroponotic visceral leishmaniasis** (*Leishmania donovani* in the Indian subcontinent), humans can serve as reservoir hosts. - For the purpose of this question, leishmaniasis is generally classified with dead-end diseases as the majority of leishmaniasis forms have zoonotic cycles where humans are incidental hosts with limited onward transmission.
Question 6: An elderly man who had been in several military conflicts during the early 1980s and received blood transfusions for injuries recently consulted his physician for a diagnosis of cryoglobulinemia and glomerulonephritis. Additional testing revealed that he was infected with a virus transmitted through blood. Which virus was involved in this infection?
- A. Hepatitis A Virus (HAV)
- B. Hepatitis B Virus (HBV)
- C. Hepatitis C Virus (HCV) (Correct Answer)
- D. Hepatitis D Virus (HDV)
Explanation: ***Hepatitis C Virus (HCV)*** - HCV infection is a common cause of **mixed cryoglobulinemia** and can lead to **glomerulonephritis**, particularly membranoproliferative glomerulonephritis. - Before widespread screening of the blood supply, HCV was a significant risk from **blood transfusions**, especially for individuals who received them in the early 1980s [1]. *Hepatitis A Virus (HAV)* - HAV is primarily transmitted via the **fecal-oral route** and does not typically cause chronic infection or lead to cryoglobulinemia or glomerulonephritis. - It causes **acute, self-limiting hepatitis** and is not associated with blood transfusions in the context described. *Hepatitis B Virus (HBV)* - While HBV can be transmitted through blood and can cause glomerulonephritis (e.g., membranous nephropathy), it is less commonly associated with **cryoglobulinemia** in comparison to HCV. - The constellation of cryoglobulinemia and glomerulonephritis, especially with a history of transfusions in the 1980s, points more strongly to HCV. *Hepatitis D Virus (HDV)* - HDV is a **defective virus** that requires co-infection with HBV to replicate. - While it can cause severe liver disease, it is not primarily associated with **cryoglobulinemia** or glomerulonephritis as a direct cause, but rather exacerbates HBV-related complications.
Question 7: A 16-year-old girl presents with a painfully enlarged lymph node in her right axilla and low grade fever. Peripheral blood counts are within normal limits. The lymph node is biopsied, and numerous granulomas filled with neutrophils and necrotic debris are observed. Which of the following organisms could produce this disease?
- A. Bartonella henselae (Correct Answer)
- B. Chlamydia psittaci
- C. Coxiella burnetii
- D. Borrelia burgdorferi
Explanation: ***Bartonella henselae*** - This organism causes **cat scratch disease (CSD)**, which typically presents with **lymphadenopathy** (often in the axilla) following a cat scratch or bite. - The characteristic histological finding in CSD is **suppurative granulomas** (granulomas with central necrosis and neutrophils), or **stellate microabscesses**, in the affected lymph nodes. *Chlamydia psittaci* - This bacterium causes **psittacosis**, primarily a respiratory illness (pneumonia) acquired from birds. - While it can cause systemic symptoms like **fever**, it is not typically associated with localized, painful suppurative lymphadenopathy or granulomas in the axilla. *Coxiella burnetii* - This organism is the causative agent of **Q fever**, which can present as an acute febrile illness, pneumonia, or hepatitis, often from exposure to infected farm animals. - It does not typically cause localized painful lymphadenopathy with suppurative granulomas in the axilla. *Borrelia burgdorferi* - This bacterium causes **Lyme disease**, characterized by an expanding erythematous rash (erythema migrans), followed by joint, cardiac, and neurological manifestations. - Primary findings do not include suppurative granulomas in lymph nodes, although general lymphadenopathy can occur.
Question 8: Which of the following statements about Kyasanur Forest Disease is false?
- A. Transmitted by bite of infective ticks
- B. Incubation period of 3 to 8 days
- C. Caused by Flavivirus
- D. Man to man transmission is seen (Correct Answer)
Explanation: ***Man to man transmission is seen*** - Kyasanur Forest Disease is primarily an **enzootic cycle** involving monkeys, rodents, and ticks; there is **no evidence of direct person-to-person transmission**. - While humans can become infected, they are considered **dead-end hosts** and do not typically transmit the virus to other humans. *Caused by Flavivirus* - **Kyasanur Forest Disease virus (KFDV)** is indeed an **RNA virus** belonging to the genus Flavivirus and the family Flaviviridae. - This classification is accurate and important for understanding its biological characteristics. *Transmitted by bite of infective ticks* - The primary vector for KFDV transmission to humans and animals is the **hard tick, Haemaphysalis spinigera**, which becomes infected after feeding on infected monkeys or other small mammals. - **Tick bites** are the main mode of transmission; direct contact with infected animals can also lead to infection. *Incubation period of 3 to 8 days* - The typical incubation period for Kyasanur Forest Disease in humans is indeed **3 to 8 days** after exposure to the virus, though it can range from 3 to 10 days. - This relatively short incubation period leads to rapid onset of symptoms once infected.
Question 9: After a renal transplant, what is the most common opportunistic infection?
- A. Varicella Zoster Virus (VZV)
- B. Coxsackie Virus
- C. Epstein-Barr Virus (EBV)
- D. Cytomegalovirus (CMV) (Correct Answer)
Explanation: ***Cytomegalovirus (CMV)*** - **CMV** is the most common opportunistic infection after renal transplantation, particularly in the first 6 months due to immunosuppression [1]. - It can cause a range of clinical syndromes, including **fever**, **leukopenia**, **gastroenteritis**, **pneumonitis**, and **hepatitis**, and can also have indirect effects that increase the risk of graft rejection. *Varicella Zoster Virus (VZV)* - While VZV can cause opportunistic infections in transplant recipients (e.g., **shingles**), it is less common than CMV [1]. - VZV typically occurs later post-transplant and is characterized by a **vesicular rash** in a dermatomal distribution. *Coxsackie Virus* - **Coxsackie virus** infections are less frequently reported as significant opportunistic infections in renal transplant recipients compared to other viral pathogens. - They are generally associated with hand-foot-and-mouth disease, herpangina, or myocarditis, which are not the most common post-transplant complications. *Epstein-Barr Virus (EBV)* - **EBV** can cause post-transplant lymphoproliferative disorder (PTLD), which is a serious complication, but EBV infection itself is not the most common opportunistic infection overall [1]. - PTLD is more common in the first year after transplant and often presents with **lymphadenopathy**, **fever**, or **graft dysfunction**.
Question 10: A 25-year-old man with 3 weeks of fever presented with tricuspid valve vegetation. The patient is an intravenous drug abuser. The most common cause of endocarditis in this patient is:
- A. Strep. viridans
- B. Pseudomonas
- C. Candida albicans
- D. Staph. aureus (Correct Answer)
Explanation: ***Staph. aureus*** - **Intravenous drug abuse (IVDA)** is a major risk factor for infective endocarditis, and *Staphylococcus aureus* is the most common causative organism, [1] particularly affecting the **tricuspid valve** on the right side of the heart. [2] - *S. aureus* can colonize the skin and needles used in IVDA, directly introducing bacteria into the bloodstream and to the heart valves. [1][3] *Strep. viridans* - *Streptococcus viridans* (viridans streptococci) is a common cause of native valve endocarditis, often following **dental procedures** or due to poor dental hygiene. [1] - It typically affects the **left-sided heart valves** (mitral or aortic) rather than the tricuspid valve, and is less commonly associated with IVDA. *Pseudomonas* - *Pseudomonas aeruginosa* can cause endocarditis, especially in IVDA patients or those with prosthetic valves, but it is **less common** than *Staphylococcus aureus* in this population. - While possible, it's not the *most common* cause specified in the question. *Candida albicans* - *Candida albicans* endocarditis is largely associated with **immunocompromised patients**, those with prosthetic valves, or prolonged use of broad-spectrum antibiotics, [4] not typically healthy IV drug abusers. - Fungal endocarditis is generally **rare** compared to bacterial endocarditis.
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