Infectious Diseases Practice Questions

Q: Cheopis index is used for

Plague. ***Plague*** - The **Cheopis index** is used to measure the **average number of Xenopsylla cheopis (oriental rat fleas)** per rat. - This index is crucial in determining the risk of **epizootic and epidemic plague**, as fleas are the primary vectors of the bacteria *Yersinia pestis*. *Infectious mononucleosis* - This viral infection, caused by the **Epstein-Barr virus**, is primarily transmitted through **saliva** and not through insect vectors. - Diagnosis involves blood tests for **heterophile antibodies** and atypical lymphocytes, not an entomological index. *Dengue fever* - Dengue is a **mosquito-borne viral illness**, primarily transmitted by **Aedes aegypti** and **Aedes albopictus** mosquitoes. - Its epidemiological surveillance focuses on mosquito indices like the **Breteau index** or **House index**, not the Cheopis index. *Typhus fever* - **Epidemic typhus** is caused by *Rickettsia prowazekii* and transmitted by the **human body louse** (*Pediculus humanus corporis*). - While other forms of typhus (e.g., murine typhus) involve fleas, the Cheopis index is specifically associated with **plague surveillance** in relation to rat fleas.

Q: The infectivity of chickenpox lasts for which of the following?

Until all lesions have crusted over. ***Correct: Until all lesions have crusted over*** - The period of **infectivity** for chickenpox (varicella-zoster virus) extends from **1-2 days before the rash appears** until **all lesions have completely crusted over**. - This is the **standard clinical endpoint** recommended by CDC, WHO, and public health guidelines for determining when a patient is no longer infectious. - Crusting typically occurs **5-7 days after rash onset**, but the endpoint is clinical (complete crusting) rather than a fixed number of days. - Once all lesions are crusted, viral shedding has effectively ceased and transmission risk is negligible. *Incorrect: Until the last scab falls off* - This is **overly cautious** and unnecessarily prolongs isolation beyond the infectious period. - Infectivity ends when lesions **crust over**, not when the dried scabs eventually fall off during the healing phase. - The scab-falling phase can take weeks and represents skin healing, not active infection. *Incorrect: 3 days after the onset of rash* - This period is **too short** as most lesions are still in the vesicular or pustular stage at 3 days. - Patients remain **highly contagious** at this stage with active viral shedding. - Releasing from isolation at this point would significantly increase transmission risk. *Incorrect: Till the fever subsides* - **Fever** typically resolves within 3-5 days, often before all skin lesions have crusted. - Patients remain **infectious** even after fever resolution if vesicular lesions are still present. - Using fever as the endpoint would result in premature release from isolation and ongoing transmission risk.

Q: All of the following are related to plague, except which of the following?

Aedes aegypti index. ***Aedes aegypti index*** - The **Aedes aegypti index** measures the prevalence of *Aedes aegypti* mosquitoes, which are vectors for diseases like **dengue**, **Zika**, **chikungunya**, and **yellow fever**. - Plague is primarily transmitted by fleas, not mosquitoes. *Total flea index* - The **total flea index** quantifies the average number of fleas per rodent, which is a direct measure of potential plague transmission risk from rodent to human populations. - A higher total flea index indicates a greater likelihood of plague outbreaks. *Burrow index* - The **burrow index** measures the number of active rodent burrows per unit area, indicating rodent population density. - Plague is maintained in **rodent populations**, and a high burrow index can suggest a sustained risk for enzootic plague. *Cheopis index* - The **Cheopis index** (or Xenopsylla cheopis index) specifically measures the average number of *Xenopsylla cheopis* (oriental rat flea) per rodent found. - *Xenopsylla cheopis* is the **primary vector** for plague transmission, making this index a critical indicator for monitoring plague risk.

Q: According to WHO guidelines for community health workers, which drug is commonly used in the management of acute respiratory infections?

Cotrimoxazole. ***Cotrimoxazole*** - **Cotrimoxazole (trimethoprim-sulfamethoxazole)** was historically recommended by WHO for community health workers in resource-limited settings for the treatment of **acute respiratory infections (ARIs)**. - It is effective against common bacterial pathogens causing ARIs, such as *Streptococcus pneumoniae* and *Haemophilus influenzae*. - **Note:** Current WHO IMCI (Integrated Management of Childhood Illness) guidelines now recommend **amoxicillin** as first-line treatment for pneumonia in children, though cotrimoxazole remains an alternative in specific contexts or where amoxicillin is unavailable. *Chloramphenicol* - **Chloramphenicol** is a potent broad-spectrum antibiotic but is generally reserved for severe infections due to potential side effects like **bone marrow suppression** (aplastic anemia). - It is not a first-line drug for routine community-level management of uncomplicated ARIs according to WHO guidelines. *Benzyl penicillin* - **Benzyl penicillin** (Penicillin G) is effective against many streptococcal infections but has a narrower spectrum compared to cotrimoxazole. - Its use in the community setting for ARIs is limited due to the need for **parenteral administration**, making it impractical for community health workers managing outpatient cases. *Gentamycin* - **Gentamycin** is an aminoglycoside antibiotic primarily used for severe Gram-negative bacterial infections, often in hospital settings. - It is administered parenterally and is not recommended by WHO for routine community-based treatment of ARIs due to the risk of **nephrotoxicity** and **ototoxicity**, and its limited effectiveness against common ARI pathogens.

Q: The multidrug regimen under the National Leprosy Eradication Programme for the treatment of all multibacillary leprosy would include which medications?

Clofazimine, rifampicin, and dapsone. ***Clofazimine, rifampicin, and dapsone*** - The standard multidrug therapy (MDT) for **multibacillary (MB) leprosy** under the National Leprosy Eradication Programme (NLEP) includes **rifampicin**, **dapsone**, and **clofazimine** [1], [2]. - This combination is crucial for effective treatment, preventing drug resistance, and minimizing relapse rates over a 12-month course [1]. *Rifampicin and dapsone* - This combination alone is typically used for **paucibacillary (PB) leprosy**, which involves fewer skin lesions and bacilli. - It lacks **clofazimine**, which is essential for adequate coverage and efficacy against the higher bacterial load seen in multibacillary leprosy [1]. *Ethionamide, rifampicin, and dapsone* - **Ethionamide** is primarily an antitubercular drug and is not part of the standard first-line regimen for leprosy [3]. - Its inclusion would be considered an off-label use or reserved for specific circumstances like **drug-resistant leprosy**, which is not the general case for all multibacillary leprosy. *Propionamide, rifampicin, and dapsone* - **Propionamide** is not a drug used in the treatment of leprosy. - This option introduces an incorrect and clinically irrelevant drug into the regimen.

Q: Which of the following countries is considered rabies-free based on the absence of indigenous cases in humans and animals?

Australia. ***Australia*** - Australia is recognized as **rabies-free** due to its strict **biosecurity measures** and geographical isolation, which prevent the introduction and spread of the virus. - There have been **no indigenous cases** of rabies in humans or terrestrial animals in Australia. *USA* - The USA has ongoing rabies cases, particularly in **wildlife reservoirs** such as raccoons, bats, skunks, and foxes, with occasional human fatalities. - While domestic animal rabies is largely controlled through vaccination, the presence of **sylvatic rabies** prevents it from being declared rabies-free. *Russia* - Russia experiences a significant number of both **animal and human rabies cases**, indicating an active circulation of the virus. - Efforts to control rabies in Russia face challenges due to its vast geography and diverse wildlife populations. *France* - While France has made significant progress in controlling rabies in domestic animals, **bat rabies** still exists, and there have been imported cases of terrestrial rabies. - France is considered to have a **controlled rabies situation** rather than being fully rabies-free, especially concerning wildlife.

Q: Which bacterial disease is commonly associated with the three "Rs": rats, rice fields, and rainfall?

Leptospirosis. ***Leptospirosis*** - This disease is directly associated with exposure to environments contaminated by **animal urine**, often linked to **rats** in environments like **rice fields** where **rainfall** creates favorable conditions for bacterial survival and transmission. - The classic **"3 Rs" mnemonic** (Rats, Rice fields, Rainfall) specifically describes leptospirosis epidemiology. - **Leptospira** bacteria typically enter the body through cuts or abrasions in the skin or through mucous membranes, especially when prolonged exposure to contaminated water occurs. - Common in **occupational groups**: farmers, sewer workers, veterinarians, and military personnel. *Bubonic plague* - Characterized by acute onset of fever, chills, weakness, and painful, swollen lymph nodes called **buboes**, caused by **Yersinia pestis**. - Primarily transmitted to humans through bites of **infected fleas** that have fed on rodents, not directly through contaminated water or rice fields. - While associated with rats, lacks the rice field and rainfall environmental components. *Haverhill fever* - Caused by **Streptobacillus moniliformis**, a form of **rat-bite fever** contracted through rodent contact or ingestion of contaminated food/water. - While associated with rats, it doesn't have the specific environmental triad of **rice fields** and **rainfall** as central to its epidemiology like leptospirosis. - Transmission is primarily through rat bites or contaminated milk products. *Melioidosis* - Caused by **Burkholderia pseudomallei**, found in soil and water in tropical and subtropical regions. - While found in water and soil with potential agricultural exposure, it is **not specifically linked** to the "rats, rice fields, and rainfall" triad that defines leptospirosis. - More commonly associated with direct soil contact rather than rat-contaminated environments.

Q: Which of the following infectious diseases is characterized by the most consistent and characteristic clinical presentation?

Measles. **Correct Option: Measles** - Measles, caused by the **measles virus**, has a highly characteristic clinical presentation including a prodrome of fever, cough, coryza, and conjunctivitis (the 3 C's), followed by **Koplik spots** (pathognomonic) and a maculopapular rash that spreads in a **cephalocaudal pattern**. - The disease progression and symptomology are quite **predictable and consistent**, making it one of the most recognizable childhood exanthems. - Clinical features follow a characteristic timeline making diagnosis reliable on clinical grounds alone. *Incorrect Option: Rubella (German Measles)* - Rubella often presents with milder and less distinctive symptoms compared to measles, including a **milder rash** and **postauricular/occipital lymphadenopathy**. - A significant number of **rubella infections are asymptomatic** or subclinical (up to 50%), making its presentation less consistent and characteristic. *Incorrect Option: Influenza* - Influenza symptoms can vary widely, ranging from **mild respiratory illness** to severe disease with pneumonia, and are often indistinguishable from other viral respiratory infections without laboratory testing. - The clinical presentation is highly variable depending on the **specific viral strain**, age, and immune status of the individual. *Incorrect Option: Polio (Poliomyelitis)* - While known for its potential to cause paralytic disease, **most poliovirus infections (about 95%) are asymptomatic** or present as mild, non-specific febrile illness without paralysis. - The variable presentation, with only a small proportion developing the characteristic paralytic form, means it lacks a consistently characteristic clinical picture for most infected individuals.

Q: Chandler's Index is used for:

Hookworm infections. **Hookworm infections** ✓ - **Chandler's Index** is a method used to assess the **severity** and **intensity** of **hookworm infection** within a community. - It calculates the average number of hookworms per infected person, helping determine prevalence and infection burden. - This epidemiological tool is specific to hookworm surveillance and control programs. *Lymphatic filariasis* - Assessed using different metrics such as microfilaremia prevalence, lymphedema rates, and circulating filarial antigen detection. - Diagnosis involves identifying **microfilariae** in blood smears, not Chandler's Index. *Intestinal ascariasis* - Assessed by detecting *Ascaris lumbricoides* eggs in stool samples. - Severity measured by worm burden or egg count intensity, not by a community-level index like Chandler's. *Dracunculiasis* - Diagnosed by the emergence of *Dracunculus medinensis* worm from the skin. - Eradication efforts focus on case detection and containment, with no application of Chandler's Index.

Q: In which of the following conditions is post-exposure prophylaxis recommended and effective?

Rabies. ***Rabies*** - **Post-exposure prophylaxis (PEP) for rabies is the gold standard example of highly effective prophylaxis**, with near **100% efficacy** when administered correctly. - Consists of **thorough wound washing**, **rabies immunoglobulin (RIG)**, and **rabies vaccine** given according to the recommended schedule. - **Universally recommended** for all animal bite exposures where rabies cannot be ruled out, as untreated rabies is **uniformly fatal**. - PEP must be initiated as soon as possible after exposure but remains effective even if started several days after the bite. *Hepatitis B* - Hepatitis B PEP is also **highly effective (70-95%)** and well-established, using **HBIG and vaccine series**. - Recommended for occupational exposures, sexual contacts, and perinatal transmission. - While very effective, rabies PEP is considered the paradigm example due to its near-perfect efficacy and the invariably fatal outcome without treatment. *Measles* - Post-exposure prophylaxis with **MMR vaccine within 72 hours** or **immunoglobulin within 6 days** can be **moderately effective**. - Time-sensitivity limits effectiveness, and vaccine may not prevent disease if given too late after exposure. - Not as universally effective as rabies PEP. *Pertussis* - **Chemoprophylaxis with azithromycin** is recommended for close contacts of pertussis cases. - However, effectiveness is **limited** - primarily reduces transmission rather than reliably preventing disease in exposed individuals. - Not considered as definitively effective as rabies or hepatitis B PEP.

Question 1

Cheopis index is used for

Accepted Answer

Plague

Answer

Infectious mononucleosis

Answer

Dengue fever

Answer

Typhus fever

Question 2

The infectivity of chickenpox lasts for which of the following?

Accepted Answer

Until all lesions have crusted over

Answer

Till the fever subsides

Answer

Until the last scab falls off

Answer

3 days after the onset of rash

Question 3

All of the following are related to plague, except which of the following?

Accepted Answer

Aedes aegypti index

Answer

Burrow index

Answer

Cheopis index

Answer

Total flea index

Question 4

According to WHO guidelines for community health workers, which drug is commonly used in the management of acute respiratory infections?

Accepted Answer

Cotrimoxazole

Answer

Chloramphenicol

Answer

Benzyl penicillin

Answer

Gentamycin

Question 5

The multidrug regimen under the National Leprosy Eradication Programme for the treatment of all multibacillary leprosy would include which medications?

Accepted Answer

Clofazimine, rifampicin, and dapsone

Answer

Rifampicin and dapsone

Answer

Ethionamide, rifampicin, and dapsone

Answer

Propionamide, rifampicin, and dapsone

Question 6

Which of the following countries is considered rabies-free based on the absence of indigenous cases in humans and animals?

Accepted Answer

Australia

Answer

USA

Answer

Russia

Answer

France

Question 7

Which bacterial disease is commonly associated with the three "Rs": rats, rice fields, and rainfall?

Accepted Answer

Leptospirosis

Answer

Bubonic plague

Answer

Haverhill fever

Answer

Melioidosis

Question 8

Which of the following infectious diseases is characterized by the most consistent and characteristic clinical presentation?

Accepted Answer

Measles

Answer

Rubella

Answer

Influenza

Answer

Polio

Question 9

Chandler's Index is used for:

Accepted Answer

Hookworm infections

Answer

Lymphatic filariasis

Answer

Intestinal ascariasis

Answer

Dracunculiasis

Question 10

In which of the following conditions is post-exposure prophylaxis recommended and effective?

Accepted Answer

Rabies

Answer

Measles

Answer

Hepatitis B

Answer

Pertussis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?