Emerging and Re-emerging Infections — MCQs

Q: A novel coronavirus outbreak is detected with high transmissibility but variable mortality across age groups. Phylogenetic analysis shows 80% similarity with SARS-CoV. To predict pandemic potential, which epidemiological parameter would be most critical to evaluate first?

Basic reproduction number (R0) and serial interval. ***Basic reproduction number (R0) and serial interval*** - The **Basic reproduction number (R0)** indicates the number of secondary infections generated by one case; an **R0 > 1** is the primary indicator of sustained transmission and pandemic potential. - The **serial interval** (time between symptom onset in successive cases) combined with **R0** allows modeling the **growth rate** of the outbreak to determine how quickly it will spread. *Cross-immunity from previous coronavirus infections* - While **cross-reactive T-cells** or antibodies can influence disease severity, they do not dictate the intrinsic **transmissibility** or early epidemic growth kinetics as directly as R0. - Assessing **herd immunity** or cross-protection is a secondary step after establishing that the pathogen has a high baseline **attack rate**. *Viral load in asymptomatic individuals only* - Monitoring **viral kinetics** in asymptomatic patients is important, but focusing **only** on this group misses the overall transmission dynamics of the entire population. - **Symptomatic transmission** often contributes significantly to the spread of respiratory viruses like SARS-like coronaviruses, making subset-only analysis insufficient for **pandemic prediction**. *Case fatality rate alone* - The **Case Fatality Rate (CFR)** measures the **virulence** or severity of the pathogen but serves as a poor predictor of how widely the virus will spread across borders. - High-mortality viruses often have lower **pandemic potential** if they kill the host too quickly to allow for wide-scale **asymptomatic or pre-symptomatic transmission**.

Q: A hospital reports increasing cases of healthcare-associated infections with Candida auris. Despite standard antifungal prophylaxis, the outbreak continues. Laboratory testing shows resistance to fluconazole and amphotericin B. What characteristic of this organism explains its epidemic potential?

Ability to form biofilms and persist on hospital surfaces. ***Ability to form biofilms and persist on hospital surfaces*** - **Candida auris** is uniquely known for its ability to form dense **biofilms**, which contribute significantly to its high level of resistance against standard **disinfectants** and **antifungals**. - Its epidemic potential is driven by its ability to persist for **weeks on environmental surfaces** and colonize the **skin of patients**, facilitating rapid **nosocomial transmission**. *Ability to survive only in human host* - Unlike many other Candida species, C. auris is highly resilient in the **extracellular environment** and can survive on **inanimate objects** like bedrails and clinical equipment. - This **environmental stability** is precisely why it causes large-scale outbreaks in healthcare settings compared to species that primarily exist as human commensals. *High virulence factors and toxin production* - While C. auris is an opportunistic pathogen, its primary threat lies in its **multidrug resistance** and **persistence** rather than the production of potent toxins. - Its **virulence** is comparable to or slightly less than **Candida albicans**, but its ability to evade treatment and control measures makes it more dangerous in hospital settings. *Rapid sporulation in aerobic environment* - **Candida auris** is a **yeast** and does not undergo **sporulation**; it reproduces via **budding**. - **Spore formation** is a characteristic of various **bacteria** (like Clostridioides difficile) or **molds**, but it is not the mechanism for yeast survival or spread in this context.

Q: A cluster of pneumonia cases is reported from a city with high mortality rate. Sputum cultures show gram-negative coccobacilli resistant to multiple antibiotics including carbapenems. Gene sequencing reveals blaNDM-1. What is the most critical factor contributing to this emerging resistance?

Horizontal gene transfer through plasmids. ***Horizontal gene transfer through plasmids*** - The **blaNDM-1** gene (New Delhi Metallo-beta-lactamase) is typically carried on highly mobile **plasmids**, enabling rapid dissemination between different bacterial species. - This mechanism is the most critical driver for the **global spread** of carbapenem resistance, often carrying multiple other resistance genes simultaneously. *Point mutations in chromosomal DNA* - While mutations can cause resistance to some drugs (like fluoroquinolones), they are **vertical** and generally slower than the rapid cluster outbreaks caused by **horizontal transfer**. - The **blaNDM-1** gene is an acquired genetic sequence, not a result of a singular point mutation in common **gram-negative coccobacilli** chromosomes. *Decreased porin expression* - Porin loss can lead to **carbapenem resistance** by preventing drug entry into the periplasm, often seen in *Pseudomonas* or *Klebsiella*. - However, this is a **structural modification** that usually works in synergy with enzymes rather than being the primary factor defined by the **blaNDM-1** gene. *Efflux pump mechanisms only* - Efflux pumps actively transport various antibiotics out of the cell, contributing to **multidrug resistance (MDR)**. - While they contribute to the phenotype, the question specifically identifies **blaNDM-1**, which is a **metallo-beta-lactamase enzyme** that enzymaticallly degrades the antibiotic, not a pump mechanism.

Q: A 42-year-old man presents with fever, severe joint pains in small joints of hands and feet, and maculopapular rash for 5 days. He returned from Caribbean islands 10 days ago. RT-PCR confirms alphavirus infection. What is the most appropriate management?

Supportive care with NSAIDs and rest. ***Supportive care with NSAIDs and rest*** - The patient presents with classic symptoms of **Chikungunya fever**, an **alphavirus** infection characterized by high fever, **maculopapular rash**, and severe, often debilitating polyarthralgia. - There is no specific **antiviral therapy** for Chikungunya; management relies on **supportive care** including **NSAIDs**, hydration, and rest to manage pain and inflammation. *Start oseltamivir therapy* - **Oseltamivir** is a neuraminidase inhibitor used specifically for the treatment and prophylaxis of **Influenza A and B**. - It has no clinical utility or mechanism of action against **alphaviruses** like Chikungunya. *Start ribavirin immediately* - **Ribavirin** is a broad-spectrum antiviral used for conditions like **Hepatitis C** or **Lassa fever**, but it is not indicated for Chikungunya. - Clinical studies have not demonstrated a significant therapeutic benefit for using **ribavirin** in acute **alphavirus** infections. *Intravenous immunoglobulin* - **IVIG** is typically reserved for severe **immunomodulatory diseases** or specific complications like Guillain-Barré syndrome. - It is not a standard or recommended treatment for the acute phase of **Chikungunya fever** and does not replace standard supportive measures.

Q: A 35-year-old farmer from Kerala presents with high-grade fever, myalgia, and altered sensorium. He has a history of contact with infected pigs. CSF examination shows lymphocytic pleocytosis. Which organism is most likely responsible?

Nipah virus. ***Nipah virus*** - The clinical triad of **encephalitis**, proximity to **Kerala**, and history of **contact with infected pigs** is classic for Nipah virus outbreaks in India. - It characteristically presents with **high-grade fever**, **altered sensorium**, and high mortality rates, often involving **lymphocytic pleocytosis** on CSF analysis. *Herpes simplex virus* - While it is a common cause of sporadic **encephalitis**, it typically targets the **temporal lobes** and is not historically linked to pig contact. - It lacks the specific **epidemiological association** with travel to or residence in Kerala pig-farming clusters. *West Nile virus* - This virus is transmitted via **Culex mosquito** bites rather than direct contact with livestock like pigs. - While it can cause neurological symptoms, it more frequently presents with **generalized weakness** or **flaccid paralysis** rather than the rapid encephalitic progression seen here. *Japanese encephalitis virus* - Although associated with pigs as amplifying hosts, JE is more commonly linked to **rice paddy** cultivation where mosquitoes breed. - JE typically presents with **thalamic involvement** on imaging and is less likely than Nipah in the context of recent high-profile Kerala outbreaks.

Q: Why has multidrug-resistant tuberculosis (MDR-TB) re-emerged as a major public health concern?

Poor treatment compliance and inadequate drug regimens. ***Poor treatment compliance and inadequate drug regimens*** - **MDR-TB** (resistance to at least **isoniazid** and **rifampicin**) primarily arises when patients do not complete their long-term treatment or take medications irregularly. - These factors exert **selective pressure** on the bacterial population, allowing resistant mutants to survive and multiply, leading to the failure of standard **DOTS** protocols. *Increased virulence of Mycobacterium tuberculosis strains* - While some strains like the **Beijing lineage** are highly transmissible, emergence of resistance is driven by **selective drug pressure** rather than inherent virulence. - Increased virulence affects the severity of the disease but does not fundamentally cause the **genetic mutations** associated with drug resistance. *Changes in bacterial cell wall structure* - While the **mycolic acid** layer provides a natural barrier to many antibiotics, **acquired resistance** in TB is typically due to specific **chromosomal mutations** (e.g., *katG* or *rpoB* genes). - Structural changes are generally a result of the resistance mechanism (like thickened cell walls in some variants) rather than the primary cause of the **MDR-TB epidemic**. *Development of new bacterial toxins* - *Mycobacterium tuberculosis* does not traditionally rely on **classic exotoxins** or **endotoxins** to cause disease or resist medications. - Resistance is a metabolic and genetic adaptation to **bactericidal agents**, and toxin production plays no known role in the resistance to **isoniazid** or **rifampicin**.

Q: What is the primary vector responsible for Chikungunya fever transmission?

Aedes aegypti and Aedes albopictus. ***Aedes aegypti and Aedes albopictus*** - These mosquitoes are the primary vectors for **Chikungunya virus**, an **alphavirus** transmitted through the bite of infected females. - Both species are also well-known for transmitting other **arboviruses** such as **Dengue**, **Zika**, and **Yellow fever**. *Anopheles mosquito* - This vector is the primary transmission route for **Plasmodium** species, which cause **Malaria**. - Unlike Aedes, Anopheles species typically bite during the **night** or during **crepuscular** hours. *Culex mosquito* - This mosquito is most notably the vector for **Japanese Encephalitis** and **West Nile virus**. - It is also the primary vector for **lymphatic filariasis** caused by **Wuchereria bancrofti** in many regions. *Mansonia mosquito* - Mansonia species are primarily recognized as the vectors for **Brugian filariasis** (**Brugia malayi**). - They are characterized by their larvae's ability to attach to the roots of **aquatic plants** to obtain oxygen.

Q: Which virus is responsible for causing Nipah virus infection, an emerging zoonotic disease with high mortality rate?

Paramyxovirus. ***Paramyxovirus*** - **Nipah virus** belongs to the family **Paramyxoviridae** and the genus **Henipavirus**, characterized by a single-stranded RNA genome. - It is a **zoonotic pathogen** primarily transmitted by **Pteropus fruit bats**, causing severe respiratory illness and fatal encephalitis. *Bunyavirus* - This family includes pathogens like **Hantavirus** and **Crimean-Congo hemorrhagic fever virus**, which are typically vector-borne or rodent-borne. - Unlike Nipah, most Bunyaviruses possess a **segmented genome** comprising three circular RNA segments. *Filovirus* - This family consists of viruses like **Ebola** and **Marburg**, which primarily cause severe **viral hemorrhagic fever**. - While both are highly lethal, Filoviruses have a distinct **filamentous structure** and are not classified under the Henipavirus genus. *Arenavirus* - This family includes the **Lassa fever virus** and is generally associated with chronic infections in **rodents**. - Arenaviruses are characterized by a **ribosome-containing** virion appearance and are not taxonomically related to the Henipavirus responsible for Nipah.

Emerging and Re-emerging Infections — MCQs

A state reports increased incidence of scrub typhus with unusual antibiotic resistance patterns. Molecular analysis reveals genetic recombination between different Orientia tsutsugamushi strains. Considering One Health approach, which integrated strategy would be most effective for long-term control?

A novel coronavirus outbreak is detected with high transmissibility but variable mortality across age groups. Phylogenetic analysis shows 80% similarity with SARS-CoV. To predict pandemic potential, which epidemiological parameter would be most critical to evaluate first?

A hospital reports increasing cases of healthcare-associated infections with Candida auris. Despite standard antifungal prophylaxis, the outbreak continues. Laboratory testing shows resistance to fluconazole and amphotericin B. What characteristic of this organism explains its epidemic potential?

A cluster of pneumonia cases is reported from a city with high mortality rate. Sputum cultures show gram-negative coccobacilli resistant to multiple antibiotics including carbapenems. Gene sequencing reveals blaNDM-1. What is the most critical factor contributing to this emerging resistance?

A 42-year-old man presents with fever, severe joint pains in small joints of hands and feet, and maculopapular rash for 5 days. He returned from Caribbean islands 10 days ago. RT-PCR confirms alphavirus infection. What is the most appropriate management?

A 35-year-old farmer from Kerala presents with high-grade fever, myalgia, and altered sensorium. He has a history of contact with infected pigs. CSF examination shows lymphocytic pleocytosis. Which organism is most likely responsible?

How does the Ebola virus cause severe hemorrhagic manifestations in infected patients?

Why has multidrug-resistant tuberculosis (MDR-TB) re-emerged as a major public health concern?

What is the primary vector responsible for Chikungunya fever transmission?

Q10

Which virus is responsible for causing Nipah virus infection, an emerging zoonotic disease with high mortality rate?

Emerging and Re-emerging Infections Indian Medical PG Practice Questions and MCQs

Question 1: A state reports increased incidence of scrub typhus with unusual antibiotic resistance patterns. Molecular analysis reveals genetic recombination between different Orientia tsutsugamushi strains. Considering One Health approach, which integrated strategy would be most effective for long-term control?

A. Development of new antibiotics for resistant strains as sole measure
B. Environmental modification, rodent control, public education, and surveillance strengthening (Correct Answer)
C. Mass chemoprophylaxis with doxycycline during outbreak season only
D. Isolation of all suspected cases in specialized centers

Explanation: ***Environmental modification, rodent control, public education, and surveillance strengthening*** - The **One Health approach** emphasizes the interconnectedness of **humans, animals, and the environment** to control zoonotic diseases like **Scrub Typhus**. - This strategy targets the **chigger vector habitat** and the **rodent reservoir**, while ensuring early detection of **emerging antibiotic resistance** through robust surveillance. *Development of new antibiotics for resistant strains as sole measure* - Relying solely on drug development fails to address the **environmental and animal drivers** of the disease cycle, leading to further **recombination and resistance**. - Antibiotic monotherapy is a reactive measure rather than a sustainable **long-term prevention** strategy. *Mass chemoprophylaxis with doxycycline during outbreak season only* - Routine use of **chemoprophylaxis** in large populations can actually accelerate the development of **antibiotic resistance** in *Orientia tsutsugamushi*. - Seasonal prophylaxis provides only temporary protection and does not reduce the **mite index** or **rodent population** in the environment. *Isolation of all suspected cases in specialized centers* - **Scrub Typhus** is not transmitted through **person-to-person** contact, so isolation is not a medically indicated or effective control measure. - Focus should be on **vector prevention** and **early diagnosis** rather than patient quarantine.

Question 2: A novel coronavirus outbreak is detected with high transmissibility but variable mortality across age groups. Phylogenetic analysis shows 80% similarity with SARS-CoV. To predict pandemic potential, which epidemiological parameter would be most critical to evaluate first?

A. Cross-immunity from previous coronavirus infections
B. Basic reproduction number (R0) and serial interval (Correct Answer)
C. Viral load in asymptomatic individuals only
D. Case fatality rate alone

Explanation: ***Basic reproduction number (R0) and serial interval*** - The **Basic reproduction number (R0)** indicates the number of secondary infections generated by one case; an **R0 > 1** is the primary indicator of sustained transmission and pandemic potential. - The **serial interval** (time between symptom onset in successive cases) combined with **R0** allows modeling the **growth rate** of the outbreak to determine how quickly it will spread. *Cross-immunity from previous coronavirus infections* - While **cross-reactive T-cells** or antibodies can influence disease severity, they do not dictate the intrinsic **transmissibility** or early epidemic growth kinetics as directly as R0. - Assessing **herd immunity** or cross-protection is a secondary step after establishing that the pathogen has a high baseline **attack rate**. *Viral load in asymptomatic individuals only* - Monitoring **viral kinetics** in asymptomatic patients is important, but focusing **only** on this group misses the overall transmission dynamics of the entire population. - **Symptomatic transmission** often contributes significantly to the spread of respiratory viruses like SARS-like coronaviruses, making subset-only analysis insufficient for **pandemic prediction**. *Case fatality rate alone* - The **Case Fatality Rate (CFR)** measures the **virulence** or severity of the pathogen but serves as a poor predictor of how widely the virus will spread across borders. - High-mortality viruses often have lower **pandemic potential** if they kill the host too quickly to allow for wide-scale **asymptomatic or pre-symptomatic transmission**.

Question 3: A hospital reports increasing cases of healthcare-associated infections with Candida auris. Despite standard antifungal prophylaxis, the outbreak continues. Laboratory testing shows resistance to fluconazole and amphotericin B. What characteristic of this organism explains its epidemic potential?

A. Ability to form biofilms and persist on hospital surfaces (Correct Answer)
B. Ability to survive only in human host
C. High virulence factors and toxin production
D. Rapid sporulation in aerobic environment

Explanation: ***Ability to form biofilms and persist on hospital surfaces*** - **Candida auris** is uniquely known for its ability to form dense **biofilms**, which contribute significantly to its high level of resistance against standard **disinfectants** and **antifungals**. - Its epidemic potential is driven by its ability to persist for **weeks on environmental surfaces** and colonize the **skin of patients**, facilitating rapid **nosocomial transmission**. *Ability to survive only in human host* - Unlike many other Candida species, C. auris is highly resilient in the **extracellular environment** and can survive on **inanimate objects** like bedrails and clinical equipment. - This **environmental stability** is precisely why it causes large-scale outbreaks in healthcare settings compared to species that primarily exist as human commensals. *High virulence factors and toxin production* - While C. auris is an opportunistic pathogen, its primary threat lies in its **multidrug resistance** and **persistence** rather than the production of potent toxins. - Its **virulence** is comparable to or slightly less than **Candida albicans**, but its ability to evade treatment and control measures makes it more dangerous in hospital settings. *Rapid sporulation in aerobic environment* - **Candida auris** is a **yeast** and does not undergo **sporulation**; it reproduces via **budding**. - **Spore formation** is a characteristic of various **bacteria** (like Clostridioides difficile) or **molds**, but it is not the mechanism for yeast survival or spread in this context.

Question 4: A cluster of pneumonia cases is reported from a city with high mortality rate. Sputum cultures show gram-negative coccobacilli resistant to multiple antibiotics including carbapenems. Gene sequencing reveals blaNDM-1. What is the most critical factor contributing to this emerging resistance?

A. Point mutations in chromosomal DNA
B. Horizontal gene transfer through plasmids (Correct Answer)
C. Decreased porin expression
D. Efflux pump mechanisms only

Explanation: ***Horizontal gene transfer through plasmids*** - The **blaNDM-1** gene (New Delhi Metallo-beta-lactamase) is typically carried on highly mobile **plasmids**, enabling rapid dissemination between different bacterial species. - This mechanism is the most critical driver for the **global spread** of carbapenem resistance, often carrying multiple other resistance genes simultaneously. *Point mutations in chromosomal DNA* - While mutations can cause resistance to some drugs (like fluoroquinolones), they are **vertical** and generally slower than the rapid cluster outbreaks caused by **horizontal transfer**. - The **blaNDM-1** gene is an acquired genetic sequence, not a result of a singular point mutation in common **gram-negative coccobacilli** chromosomes. *Decreased porin expression* - Porin loss can lead to **carbapenem resistance** by preventing drug entry into the periplasm, often seen in *Pseudomonas* or *Klebsiella*. - However, this is a **structural modification** that usually works in synergy with enzymes rather than being the primary factor defined by the **blaNDM-1** gene. *Efflux pump mechanisms only* - Efflux pumps actively transport various antibiotics out of the cell, contributing to **multidrug resistance (MDR)**. - While they contribute to the phenotype, the question specifically identifies **blaNDM-1**, which is a **metallo-beta-lactamase enzyme** that enzymaticallly degrades the antibiotic, not a pump mechanism.

Question 5: A 42-year-old man presents with fever, severe joint pains in small joints of hands and feet, and maculopapular rash for 5 days. He returned from Caribbean islands 10 days ago. RT-PCR confirms alphavirus infection. What is the most appropriate management?

A. Start oseltamivir therapy
B. Supportive care with NSAIDs and rest (Correct Answer)
C. Start ribavirin immediately
D. Intravenous immunoglobulin

Explanation: ***Supportive care with NSAIDs and rest*** - The patient presents with classic symptoms of **Chikungunya fever**, an **alphavirus** infection characterized by high fever, **maculopapular rash**, and severe, often debilitating polyarthralgia. - There is no specific **antiviral therapy** for Chikungunya; management relies on **supportive care** including **NSAIDs**, hydration, and rest to manage pain and inflammation. *Start oseltamivir therapy* - **Oseltamivir** is a neuraminidase inhibitor used specifically for the treatment and prophylaxis of **Influenza A and B**. - It has no clinical utility or mechanism of action against **alphaviruses** like Chikungunya. *Start ribavirin immediately* - **Ribavirin** is a broad-spectrum antiviral used for conditions like **Hepatitis C** or **Lassa fever**, but it is not indicated for Chikungunya. - Clinical studies have not demonstrated a significant therapeutic benefit for using **ribavirin** in acute **alphavirus** infections. *Intravenous immunoglobulin* - **IVIG** is typically reserved for severe **immunomodulatory diseases** or specific complications like Guillain-Barré syndrome. - It is not a standard or recommended treatment for the acute phase of **Chikungunya fever** and does not replace standard supportive measures.

Question 6: A 35-year-old farmer from Kerala presents with high-grade fever, myalgia, and altered sensorium. He has a history of contact with infected pigs. CSF examination shows lymphocytic pleocytosis. Which organism is most likely responsible?

A. Herpes simplex virus
B. Nipah virus (Correct Answer)
C. West Nile virus
D. Japanese encephalitis virus

Explanation: ***Nipah virus*** - The clinical triad of **encephalitis**, proximity to **Kerala**, and history of **contact with infected pigs** is classic for Nipah virus outbreaks in India. - It characteristically presents with **high-grade fever**, **altered sensorium**, and high mortality rates, often involving **lymphocytic pleocytosis** on CSF analysis. *Herpes simplex virus* - While it is a common cause of sporadic **encephalitis**, it typically targets the **temporal lobes** and is not historically linked to pig contact. - It lacks the specific **epidemiological association** with travel to or residence in Kerala pig-farming clusters. *West Nile virus* - This virus is transmitted via **Culex mosquito** bites rather than direct contact with livestock like pigs. - While it can cause neurological symptoms, it more frequently presents with **generalized weakness** or **flaccid paralysis** rather than the rapid encephalitic progression seen here. *Japanese encephalitis virus* - Although associated with pigs as amplifying hosts, JE is more commonly linked to **rice paddy** cultivation where mosquitoes breed. - JE typically presents with **thalamic involvement** on imaging and is less likely than Nipah in the context of recent high-profile Kerala outbreaks.

Question 7: How does the Ebola virus cause severe hemorrhagic manifestations in infected patients?

A. Direct cytopathic effect on hepatocytes only
B. Selective destruction of bone marrow
C. Inhibition of interferon response and targeting of endothelial cells with coagulation dysfunction (Correct Answer)
D. Autoimmune destruction of platelets

Explanation: ***Inhibition of interferon response and targeting of endothelial cells with coagulation dysfunction*** - Ebola virus proteins **VP24 and VP35** antagonize the host immune response by blocking **interferon production and signaling**, allowing rapid viral replication. - The virus infects **monocytes and macrophages**, triggering a massive release of **pro-inflammatory cytokines** and damaging **endothelial cells**, which leads to **Disseminated Intravascular Coagulation (DIC)** and severe hemorrhage. *Direct cytopathic effect on hepatocytes only* - While the virus does cause **hepatocyte necrosis** leading to impaired synthesis of clotting factors, it is not limited to this cell type. - Hemorrhage is a result of a **systemic cytokine storm** and widespread **endothelial dysfunction**, rather than isolated liver damage. *Selective destruction of bone marrow* - Ebola can cause **lymphocyte apoptosis** and affect hematopoiesis, but it does not cause a selective or complete destruction of the **bone marrow**. - The primary cause of bleeding in Ebola is **consumption coagulopathy** (DIC) rather than primary **aplastic anemia**. *Autoimmune destruction of platelets* - Thrombocytopenia in Ebola is caused by **sequestration and consumption** during DIC, not by an **autoimmune Type II hypersensitivity** mechanism. - The pathogen-induced **vascular leak** and microvascular thrombi are the drivers of the clinical presentation, not chronic **anti-platelet antibodies**.

Question 8: Why has multidrug-resistant tuberculosis (MDR-TB) re-emerged as a major public health concern?

A. Poor treatment compliance and inadequate drug regimens (Correct Answer)
B. Increased virulence of Mycobacterium tuberculosis strains
C. Changes in bacterial cell wall structure
D. Development of new bacterial toxins

Explanation: ***Poor treatment compliance and inadequate drug regimens*** - **MDR-TB** (resistance to at least **isoniazid** and **rifampicin**) primarily arises when patients do not complete their long-term treatment or take medications irregularly. - These factors exert **selective pressure** on the bacterial population, allowing resistant mutants to survive and multiply, leading to the failure of standard **DOTS** protocols. *Increased virulence of Mycobacterium tuberculosis strains* - While some strains like the **Beijing lineage** are highly transmissible, emergence of resistance is driven by **selective drug pressure** rather than inherent virulence. - Increased virulence affects the severity of the disease but does not fundamentally cause the **genetic mutations** associated with drug resistance. *Changes in bacterial cell wall structure* - While the **mycolic acid** layer provides a natural barrier to many antibiotics, **acquired resistance** in TB is typically due to specific **chromosomal mutations** (e.g., *katG* or *rpoB* genes). - Structural changes are generally a result of the resistance mechanism (like thickened cell walls in some variants) rather than the primary cause of the **MDR-TB epidemic**. *Development of new bacterial toxins* - *Mycobacterium tuberculosis* does not traditionally rely on **classic exotoxins** or **endotoxins** to cause disease or resist medications. - Resistance is a metabolic and genetic adaptation to **bactericidal agents**, and toxin production plays no known role in the resistance to **isoniazid** or **rifampicin**.

Question 9: What is the primary vector responsible for Chikungunya fever transmission?

A. Aedes aegypti and Aedes albopictus (Correct Answer)
B. Anopheles mosquito
C. Culex mosquito
D. Mansonia mosquito

Explanation: ***Aedes aegypti and Aedes albopictus*** - These mosquitoes are the primary vectors for **Chikungunya virus**, an **alphavirus** transmitted through the bite of infected females. - Both species are also well-known for transmitting other **arboviruses** such as **Dengue**, **Zika**, and **Yellow fever**. *Anopheles mosquito* - This vector is the primary transmission route for **Plasmodium** species, which cause **Malaria**. - Unlike Aedes, Anopheles species typically bite during the **night** or during **crepuscular** hours. *Culex mosquito* - This mosquito is most notably the vector for **Japanese Encephalitis** and **West Nile virus**. - It is also the primary vector for **lymphatic filariasis** caused by **Wuchereria bancrofti** in many regions. *Mansonia mosquito* - Mansonia species are primarily recognized as the vectors for **Brugian filariasis** (**Brugia malayi**). - They are characterized by their larvae's ability to attach to the roots of **aquatic plants** to obtain oxygen.

Question 10: Which virus is responsible for causing Nipah virus infection, an emerging zoonotic disease with high mortality rate?

A. Bunyavirus
B. Filovirus
C. Arenavirus
D. Paramyxovirus (Correct Answer)

Explanation: ***Paramyxovirus*** - **Nipah virus** belongs to the family **Paramyxoviridae** and the genus **Henipavirus**, characterized by a single-stranded RNA genome. - It is a **zoonotic pathogen** primarily transmitted by **Pteropus fruit bats**, causing severe respiratory illness and fatal encephalitis. *Bunyavirus* - This family includes pathogens like **Hantavirus** and **Crimean-Congo hemorrhagic fever virus**, which are typically vector-borne or rodent-borne. - Unlike Nipah, most Bunyaviruses possess a **segmented genome** comprising three circular RNA segments. *Filovirus* - This family consists of viruses like **Ebola** and **Marburg**, which primarily cause severe **viral hemorrhagic fever**. - While both are highly lethal, Filoviruses have a distinct **filamentous structure** and are not classified under the Henipavirus genus. *Arenavirus* - This family includes the **Lassa fever virus** and is generally associated with chronic infections in **rodents**. - Arenaviruses are characterized by a **ribosome-containing** virion appearance and are not taxonomically related to the Henipavirus responsible for Nipah.

Practice by Chapter

Factors in Emergence of New Infections

Practice Questions

Pandemic Preparedness

Practice Questions

Emerging Viral Infections

Practice Questions

Emerging Bacterial Infections

Practice Questions

Emerging Fungal Infections

Practice Questions

Emerging Parasitic Infections

Practice Questions

Emerging Antimicrobial Resistance

Practice Questions

Bioterrorism Agents

Practice Questions

Global Response to Emerging Infections

Practice Questions

Disease Surveillance Systems

Practice Questions

One Health Approach

Practice Questions

Climate Change and Infectious Diseases

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free