Infectious Diseases Practice Questions

Q: Low osmolarity ORS - false statement is

Osmolarity is 311 mosm/liter. ***Osmolarity is 311 mosm/liter*** - Low osmolarity ORS has an osmolarity of **245 mOsm/L**, calculated as: **Sodium 75 + Potassium 20 + Chloride 65 + Glucose 75 + Citrate 10 = 245 mOsm/L**. - An osmolarity of **311 mOsm/L** corresponds to the **standard WHO ORS**, not the low osmolarity ORS which was developed to reduce osmotic load. *Sodium concentration 75 mmol/liter* - This statement is **true** for low osmolarity ORS, as its sodium concentration is indeed **75 mmol/L**. - The reduced sodium concentration (compared to **90 mmol/L** in standard ORS) helps achieve the lower overall osmolarity. *Potassium is 20 mmol/liter* - This statement is **true** for low osmolarity ORS, as it contains **20 mmol/L of potassium**. - Potassium is crucial for replacing **electrolyte losses** in diarrhea and maintaining intracellular fluid balance. *Glucose concentration 75 mmol/liter* - This statement is also **true** for low osmolarity ORS, with a glucose concentration of **75 mmol/L (13.5 g/L)**. - The glucose promotes **sodium-glucose co-transport** in the intestine, facilitating water absorption despite lower sodium concentration.

Q: Plague is transmitted by the bite of -

Rat flea. **Correct Answer: Rat flea** - Plague, caused by the bacterium *Yersinia pestis*, is primarily transmitted to humans through the bite of an infected **rat flea** (most commonly *Xenopsylla cheopis*) - The fleas acquire the bacteria by feeding on infected rodents and then transmit it to humans when they bite *Incorrect: Tse-Tse fly* - The **Tse-Tse fly** is the primary vector for **African trypanosomiasis** (sleeping sickness), caused by species of *Trypanosoma* - This fly is not associated with the transmission of plague *Incorrect: Culex mosquito* - The **Culex mosquito** is known to transmit several diseases, including **West Nile virus**, **Japanese encephalitis**, and **filariasis** - It is not a vector for the plague bacterium *Yersinia pestis* *Incorrect: Body louse* - The **body louse** (*Pediculus humanus corporis*) is a vector for diseases such as **epidemic typhus** (caused by *Rickettsia prowazekii*) and **relapsing fever** (caused by *Borrella recurrentis*) - It does not transmit plague

Q: Which one of the following is not a strategy under Roll Back Malaria?

Development of new antimalarial drugs. ***Development of new antimalarial drugs*** - While research and development of antimalarial drugs is important for global malaria control, it is **NOT one of the core strategic pillars** of the Roll Back Malaria (RBM) partnership - RBM focuses on **implementing existing interventions** rather than drug development, which falls under research organizations like MMV (Medicines for Malaria Venture) - The RBM partnership emphasizes **access to and quality of existing treatments** rather than development of new drugs *Anti-larval measures* - Anti-larval measures (larvicides, environmental management, source reduction) are part of **integrated vector management (IVM)** strategies - While not explicitly listed as one of the four main pillars, they are included under broader vector control approaches alongside ITNs and IRS - These measures complement the prevention strategies promoted by RBM *Strengthening of health system* - This is a **core strategic component** of Roll Back Malaria, essential for effective delivery of malaria interventions - Strong health systems ensure prompt diagnosis, treatment access, commodity supply chains, and surveillance - Health system strengthening enables sustainable malaria control programs *Use of insecticide treated bed nets* - This is a **primary prevention strategy** and core pillar of the Roll Back Malaria partnership - **ITNs (Insecticide Treated Nets)** are highly effective in reducing malaria transmission by protecting individuals from mosquito bites - Mass distribution of ITNs is one of the most successful RBM interventions in endemic areas

Q: Infective period of chicken pox is

2 days before and 5 days after rash appearance. ***2 days before and 5 days after rash appearance*** - The **infective period** for **chickenpox (varicella)** begins approximately **1-2 days before the rash appears** and continues until **all lesions have crusted over**, which typically occurs around **5-7 days after rash onset**. - According to **CDC guidelines** and standard medical references, patients are contagious from 1-2 days prior to rash onset until all vesicles are scabbed. - The timeframe of **2 days before and 5 days after** represents the **clinically accepted standard** for isolation and infection control purposes. *4 days before and 5 days after rash appearance* - This option **overestimates the start of the infective period**. - The incubation period of chickenpox is 10-21 days, but **infectivity does not begin 4 days before rash** - it starts only 1-2 days prior. - This extended timeframe is not supported by standard medical literature. *4 days before and 4 days after rash appearance* - This option **overestimates when infectivity begins** and **underestimates the duration after rash onset**. - Infectivity starts 1-2 days before rash, not 4 days before. - The period after rash onset should extend until all lesions are crusted (typically 5-7 days). *2 days before and 2 days after rash appearance* - While this option correctly identifies when infectivity begins, it **significantly underestimates the duration after rash onset**. - Patients remain contagious until **all lesions have crusted over**, which usually takes **5-7 days** after rash appearance, not just 2 days. - Premature discontinuation of isolation at 2 days would pose significant infection control risks.

Q: 'S-A-F-E program' was initiated for the control of which of the following conditions?

Trachoma. ***Trachoma*** - The **S-A-F-E program** is a comprehensive strategy developed by the World Health Organization (WHO) for the elimination of blinding **trachoma**. - **S-A-F-E** stands for **Surgery** for trichiasis, **Antibiotics** for infection, **Facial cleanliness**, and **Environmental improvement**. *Ocular trauma* - While ocular trauma is a significant cause of vision impairment, its control and prevention strategies are distinct from the specific interventions of the SAFE program. - Management of ocular trauma focuses on immediate medical attention, surgical repair, and preventive measures like protective eyewear. *Onchocerciasis* - **Onchocerciasis**, also known as river blindness, is controlled primarily through mass drug administration of **ivermectin**, alongside vector control. - This condition is caused by a parasitic worm (**Onchocerca volvulus**) and is not targeted by the SAFE program. *Refractive error* - **Refractive errors** (e.g., myopia, hyperopia, astigmatism) are corrected with spectacles, contact lenses, or refractive surgery. - They are not infectious diseases and do not require the public health interventions outlined in the SAFE program.

Q: All are true about communicability of Malaria, except-

The number of gametocytes in blood increases with time. ***The number of gametocytes in blood increases with time*** - This statement is incorrect because the **density of gametocytes typically decreases** after reaching an early peak, especially as the host's immune response develops. - While gametocytes are essential for transmission, their numbers don't continuously increase; rather, they are produced for a period and then clear, unless chronic infection or re-infection occurs. *Gametocytes appear in blood 4-5 days after the appearance of the asexual parasite, in vivax infection.* - This statement is correct. In **_Plasmodium vivax_ infections**, gametocytes mature relatively quickly, becoming detectable in the bloodstream within a few days of asexual parasite appearance. - This rapid development contributes to the early transmissibility of *P. vivax*. *In the early stage of infection, their density may exceed 1000 per cmm of blood.* - This statement is correct. Particularly in **hyperparasitemic infections** with species like *P. falciparum* or *P. vivax*, high densities of gametocytes can be observed in the early stages, making the individual highly infectious to mosquitoes. - A high gametocyte density significantly increases the probability of transmission to a feeding mosquito. *Gametocytes appear in blood 10-12 days after the appearance of asexual parasite, in falciparum infection.* - This statement is correct. **_Plasmodium falciparum_ gametocytes** take longer to mature and become detectable in the peripheral blood compared to *P. vivax*. - This delayed appearance of *P. falciparum* gametocytes means that individuals may be symptomatic and treated for asexual parasites before becoming fully infectious to mosquitoes.

Q: The SAFE strategy is used for elimination of?

Trachoma. ***Trachoma*** - The **SAFE strategy** (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) is the World Health Organization's primary intervention for eliminating blinding **trachoma**. - It addresses the various aspects of **trachoma transmission** and progression, from treating active infection to preventing reinfection and managing trichiasis. *Bacterial conjunctivitis* - This condition is typically treated with **topical antibiotics** and does not require a comprehensive, multi-component public health strategy like SAFE. - It is generally self-limiting and rarely leads to **blinding complications** or necessitates surgical intervention. *Onchocerciasis* - Also known as **river blindness**, this parasitic disease is primarily controlled through mass drug administration with **ivermectin**. - While it can cause severe visual impairment, its transmission cycle and treatment differ significantly from those addressed by the SAFE strategy. *Viral conjunctivitis* - This is usually a **self-limiting condition** for which there is no specific antiviral treatment, and management is primarily supportive. - It does not involve bacterial infection, chronic inflammation leading to fibrosis, or require the **public health interventions** outlined in the SAFE strategy.

Q: Which of the following is not a STD -

Hepatitis A. ***Hepatitis A*** - **Hepatitis A** is primarily transmitted via the **fecal-oral route** through contaminated food or water, NOT through sexual contact. - While rare transmission can occur through oral-anal contact during sexual activity, it is **not classified as a sexually transmitted disease (STD)**. - Hepatitis A is a vaccine-preventable disease and is NOT included in standard STD classifications. *Amoebiasis* - **Amoebiasis**, caused by *Entamoeba histolytica*, is primarily a **gastrointestinal parasitic infection** transmitted through the **fecal-oral route** via contaminated food or water. - While it can occasionally be transmitted through oral-anal sexual contact (particularly in MSM populations), it is **not traditionally classified as an STD** in standard medical literature. - **NOTE**: This option is also debatable as "not an STD" and creates potential ambiguity in the question. *Herpes simplex type 1* - **Herpes simplex virus type 1 (HSV-1)** can cause both oral herpes (cold sores) and genital herpes through oral-genital sexual contact. - HSV-1 is increasingly recognized as a cause of **genital herpes** and is transmitted sexually, making it an **STD**. - While HSV-2 is the classic genital herpes virus, HSV-1 genital infections are becoming more common. *Scabies* - **Scabies** is a skin infestation caused by *Sarcoptes scabiei* mite, transmitted through **prolonged close physical contact**, including sexual contact. - It is **recognized as an STD** because sexual contact is a common mode of transmission in adults. - Scabies is highly contagious and easily spreads between sexual partners.

Question 1

A dentist suffered from Hepatitis B infection 3 months back. His liver function tests are normal, but HBsAg remains positive and he is not allowed by the medical board to do surgical practice. He is:

Accepted Answer

Healthy carrier

Answer

Inactive carrier

Answer

Convalescent carrier

Answer

Paradoxical carrier

Question 2

Low osmolarity ORS - false statement is

Accepted Answer

Osmolarity is 311 mosm/liter

Answer

Sodium concentration 75 mmol/liter

Answer

Potassium is 20 mmol/liter

Answer

Glucose concentration 75 mmol/liter

Question 3

Plague is transmitted by the bite of -

Accepted Answer

Rat flea

Answer

Tse-Tse fly

Answer

Culex mosquito

Answer

Body louse

Question 4

Which one of the following is not a strategy under Roll Back Malaria?

Accepted Answer

Development of new antimalarial drugs

Answer

Anti-larval measures

Answer

Strengthening of health system

Answer

Use of insecticide treated bed nets

Question 5

Infective period of chicken pox is

Accepted Answer

2 days before and 5 days after rash appearance

Answer

4 days before and 5 days after rash appearance

Answer

4 days before and 4 days after rash appearance

Answer

2 days before and 2 days after rash appearance

Question 6

'S-A-F-E program' was initiated for the control of which of the following conditions?

Accepted Answer

Trachoma

Answer

Ocular trauma

Answer

Onchocerciasis

Answer

Refractive error

Question 7

The most effective method of reduction of incidence of institutional pediatric *Staphylococcus aureus* infection is:

Accepted Answer

Meticulous handwashing before and after contact with patients

Answer

Routine isolation of culture positive

Answer

Mask and gloves use with each suspected patient

Answer

Treatment of all culture positive patients with vancomycin

Question 8

All are true about communicability of Malaria, except-

Accepted Answer

The number of gametocytes in blood increases with time

Answer

Gametocytes appear in blood 4-5 days after the appearance of the asexual parasite, in vivax infection.

Answer

In the early stage of infection, their density may exceed 1000 per cmm of blood.

Answer

Gametocytes appear in blood 10-12 days after the appearance of asexual parasite, in falciparum infection.

Question 9

The SAFE strategy is used for elimination of?

Accepted Answer

Trachoma

Answer

Bacterial conjunctivitis

Answer

Onchocerciasis

Answer

Viral conjunctivitis

Question 10

Which of the following is not a STD -

Accepted Answer

Hepatitis A

Answer

Amoebiasis

Answer

Herpes simplex type 1

Answer

Scabies

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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