NEET-PG 2015 Practice Questions

Q: Which of the following infectious diseases has the highest proportion of asymptomatic chronic carriers?

Hepatitis B. ***Hepatitis B*** - **Hepatitis B** infection has a significant proportion of **chronic asymptomatic carriers**, particularly when infection occurs perinatally or in early childhood. - In adults, approximately **5% develop chronic infection** after acute exposure, and many of these chronic carriers remain asymptomatic while maintaining infectivity. - Chronic carriers can harbor the virus for years or decades without clinical symptoms, making them an important reservoir for transmission. - This is a major public health concern as asymptomatic carriers can unknowingly transmit the virus. *Measles* - **Measles** is highly contagious and typically presents with **symptomatic disease** in nearly all infected individuals. - Clinical features include characteristic maculopapular rash, cough, coryza, conjunctivitis, and Koplik's spots. - Asymptomatic infection is **extremely rare** with measles virus. *Diphtheria* - While **asymptomatic pharyngeal carriage** of *Corynebacterium diphtheriae* can occur, it is not the predominant pattern. - Clinical diphtheria typically presents with pseudomembrane formation, sore throat, and potential systemic toxin effects. - Carrier rates vary but are not as epidemiologically significant as with Hepatitis B. *Rabies* - **Rabies** is almost **100% symptomatic** once the virus reaches the central nervous system. - There is **no chronic asymptomatic carrier state** in humans. - Once clinical symptoms appear (encephalitis, hydrophobia, paralysis), the disease is virtually always fatal.

Q: Which of the following statements about influenza infectivity is correct?

All of the options are correct.. ***All of the options are correct.*** - All statements provided accurately describe aspects of influenza infectivity and epidemiology. - The **communicable period**, the **primary source of infection**, and the potential for **subclinical cases** are all characteristic features of influenza. *Communicable period is 1 day before to 5-7 days after the onset of symptoms* - This statement is accurate, as influenza is transmissible **before symptom onset** and for several days afterward, which contributes to its rapid spread. - Peak viral shedding often occurs just before and in the first few days of symptomatic illness. - Adults typically shed virus from 1 day before to 5-7 days after symptom onset (can be longer in children and immunocompromised individuals). *The primary source of infection is a clinical case.* - This is correct, as **symptomatic individuals (clinical cases) are the PRIMARY source** of influenza virus transmission to others. - Respiratory droplets produced by coughing, sneezing, or talking from an infected person are the main mode of spread. - While subclinical cases can transmit, clinical cases with overt symptoms produce more respiratory droplets and are the major drivers of transmission. *There can be subclinical cases of influenza.* - This statement is correct; many individuals infected with influenza virus experience **mild or asymptomatic infections** (subclinical cases). - These subclinical cases can still transmit the virus, though typically to a lesser extent than symptomatic cases, further complicating control efforts.

Q: Vaccine derived polio virus outbreaks are due to?

Type-2 poliovirus. ***Type-2 poliovirus*** - The **type 2 poliovirus (PV2)** component of the oral polio vaccine (OPV) has historically been associated with the majority of vaccine-derived poliovirus (VDPV) outbreaks. - The **attenuated PV2 strain** in OPV can revert to neurovirulent forms in rare cases, leading to outbreaks, especially in areas with low vaccination coverage. - Type 2 was responsible for **>90% of circulating VDPV (cVDPV) cases**, which led to the global switch from trivalent OPV to bivalent OPV (without type 2) in April 2016. *Type-3 poliovirus* - While **type 3 poliovirus (PV3)** was also part of OPV, **wild type 3 poliovirus was declared eradicated in 2019** (last case in 2012). - VDPV outbreaks due to PV3 are rare compared to PV2. *Type-1 poliovirus* - **Type 1 poliovirus (PV1)** is still endemic in some regions and causes wild poliovirus (WPV) infections. - Although PV1 is included in bivalent OPV, **VDPV outbreaks** from the PV1 component are very rare compared to PV2. *All types of poliovirus* - While all three serotypes of poliovirus were historically included in trivalent OPV, **PV2 is overwhelmingly responsible** for VDPV outbreaks. - **Wild type 2 poliovirus was eradicated in 2015** (last case 1999), but the vaccine strain continued to cause VDPV outbreaks until type 2 was removed from routine OPV.

Q: Which of the following statements regarding polio vaccination is false?

First OPV is given at 4 weeks. ***First OPV is given at 4 weeks*** - The first dose of **Oral Polio Vaccine (OPV)** is typically given at birth, often referred to as the **"zero dose,"** before the 4-week mark. - Subsequent doses are given at 6, 10, and 14 weeks of age as part of the routine immunization schedule, making the statement that the first OPV is given at 4 weeks false. *OPV induces both humoral and intestinal immunity* - **OPV** is a **live attenuated vaccine** that replicates in the gut, thereby stimulating both a systemic **humoral immune response** (producing antibodies in the bloodstream) and **local intestinal immunity** (IgA antibodies in the gut). - This **intestinal immunity** is crucial for preventing viral replication in the gut and reducing transmission. *IPV is given intramuscularly* - The **Inactivated Polio Vaccine (IPV)**, also known as the **Salk vaccine**, is administered via injection, specifically through the **intramuscular route**. - This method ensures systemic absorption and the development of **humoral immunity**. *Both killed and live vaccines are available* - There are two main types of polio vaccines: **Oral Polio Vaccine (OPV)**, which is a **live attenuated vaccine**, and **Inactivated Polio Vaccine (IPV)**, which is a **killed vaccine**. - Both types have been instrumental in polio eradication efforts, each with distinct advantages and disadvantages.

Q: Reservoir of infection in enteric fever?

Man. ***Man*** - Humans are the **sole natural reservoir** for *Salmonella Typhi* and *Salmonella Paratyphi*, the causative agents of enteric fever (typhoid and paratyphoid fever). - The bacteria can persist in the **gallbladder** of asymptomatic carriers, who can then shed the bacteria in their feces, contributing to transmission. *Birds* - Birds are not considered a primary reservoir for the **causative pathogens of enteric fever** (*Salmonella Typhi* or *Paratyphi*). - They are more commonly associated with other *Salmonella* serotypes, such as *Salmonella Enteritidis*, which cause **gastroenteritis** rather than systemic enteric fever. *Cow* - Cows are not a primary reservoir for the organisms responsible for **enteric fever**; these pathogens are specifically adapted to humans. - While cows can carry various *Salmonella* species, they are typically associated with **foodborne outbreaks** of *Salmonella*-induced **gastroenteritis**, not typhoid fever. *Water* - Water is a **vehicle for transmission** of enteric fever, becoming contaminated with human feces containing *Salmonella Typhi* or *Paratyphi*. - It is not a reservoir because the bacteria do not naturally **multiply or persist indefinitely** in water without a human source.

Q: What is the Hib conjugate vaccine made of?

Capsular polysaccharide with carrier. ***Capsular polysaccharide with carrier*** - The Hib conjugate vaccine uses a **polysaccharide capsule** from *Haemophilus influenzae* type b (Hib) covalently linked to a **protein carrier** [1]. - This conjugation allows activated B cells to present the polysaccharide to T helper cells, inducing a strong **T-cell dependent immune response** and **immunological memory**, especially in infants [1]. *Capsular polysaccharide* - A vaccine made only of **capsular polysaccharide** would be a **polysaccharide vaccine**, which induces a **T-cell independent immune response**. - This type of vaccine is **poorly immunogenic in infants** and does not generate long-lasting memory. *Purified protein with carrier* - This describes components of some **protein subunit vaccines**, but not specifically the Hib vaccine, which targets the polysaccharide capsule. - While it employs a carrier protein, the primary antigen is the **polysaccharide**, not a purified bacterial protein. *Cell wall polysaccharide* - The Hib vaccine specifically targets the **capsular polysaccharide**, which is distinct from the general cell wall polysaccharides found in the bacterial outer membrane. - The **capsule** is the primary virulence factor and target for protective immunity in Hib.

Q: What is a common characteristic of the H5N1 and H7N7 strains of influenza?

Strains of avian influenza. ***Strains of avian influenza*** - Both **H5N1** and **H7N7** are well-known subtypes of the **influenza A virus** that primarily infect birds. - While they can infect humans, their natural reservoir and main hosts are **avian species**. *Frequent endemic infection in man* - These strains are not endemic in humans; human infections are typically **sporadic** and associated with close contact with infected birds. - They lack efficient **human-to-human transmission**, which prevents them from becoming endemic in the human population. *Have same frequency of antigenic variation* - Although both undergo **antigenic variation**, the specific frequency and patterns can differ between strains and are influenced by various factors, including their host range and circulation dynamics. - It is inaccurate to assume identical frequencies of **antigenic drift** and **shift** for different viral subtypes. *None of the options* - This option is incorrect because "Strains of avian influenza" is a correct and common characteristic shared by both H5N1 and H7N7.

Q: Capsular polysaccharide derived vaccine is available for all meningococci except?

Group B. ***Group B*** - The capsular polysaccharide of **Group B meningococci** is composed of **polysialic acid**, which is poorly immunogenic in humans because it structurally mimics human neural cell adhesion molecules. - Due to its **poor immunogenicity** and risk of autoantibody production, traditional polysaccharide vaccines are ineffective against Group B. *Group A* - Polysaccharide vaccines for **Group A meningococci** (e.g., in Menactra, Menveo) are effective in inducing a protective immune response. - Group A is a major cause of meningococcal disease, particularly in the **"meningitis belt"** of sub-Saharan Africa. *Group C* - **Capsular polysaccharide vaccines** are available and effective against Group C meningococcal disease, often included in quadrivalent formulations. - These vaccines elicit a robust **antibody response** against the Group C polysaccharide. *Group Y* - Vaccines containing the **capsular polysaccharide** of Group Y meningococci are effective and commonly included in quadrivalent vaccines. - Group Y is a significant cause of meningococcal disease, particularly in **North America and Europe**.

Q: Which of the following statements regarding Pertussis is INCORRECT?

Cerebellar ataxia is a known complication.. ***Cerebellar ataxia is a known complication.*** - **Cerebellar ataxia** is not a typical or known complication of pertussis. Complications usually involve the respiratory, neurological (e.g., seizures, encephalopathy due to hypoxia), and nutritional systems due to severe coughing. - While neurological complications can occur, **ataxia** specifically is not frequently sighted in the context of pertussis. *Some infections may be subclinical.* - Some individuals, especially those partially immunized or older, can experience **subclinical or atypical infections** with pertussis, often presenting as a mild cough. - This characteristic makes it difficult to control the spread of the disease as infected individuals may not be recognized. *The most infective stage is the catarrhal stage.* - The **catarrhal stage**, characterized by non-specific cold-like symptoms, is the most contagious phase because bacterial shedding is highest. - During this stage, symptoms are mild and often indistinguishable from a common cold, leading to widespread transmission before diagnosis. *The drug of choice is Erythromycin.* - **Erythromycin**, or other macrolides like azithromycin or clarithromycin, are the drugs of choice for treating pertussis. - These antibiotics are most effective when administered early in the **catarrhal stage** to reduce disease severity and prevent transmission.

Q: Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?

Acyclovir. ***Acyclovir*** - **Acyclovir** is an antiviral medication specifically used to treat infections caused by **herpes viruses** (e.g., HSV, VZV), not influenza viruses. - It works by inhibiting **viral DNA polymerase**, a mechanism distinct from how anti-influenza drugs act. - **This drug has never been indicated for influenza** - it is the correct answer to this "not indicated" question. *Amantadine* - **Amantadine** is an M2 ion channel inhibitor that **was indicated** for influenza A treatment and prophylaxis. - Although no longer recommended due to widespread **resistance** among circulating influenza strains, it remains a drug that was formally indicated for seasonal influenza. *Rimantadine* - **Rimantadine** is also an M2 ion channel inhibitor, structurally related to amantadine, with a similar mechanism of action. - Like amantadine, it **was indicated** for influenza treatment or prophylaxis but is no longer recommended due to high rates of **resistance** in circulating influenza A viruses. *Oseltamivir* - **Oseltamivir** is a **neuraminidase inhibitor** currently approved and recommended for the treatment and prophylaxis of both influenza A and B. - It reduces viral spread by preventing the release of new virions from infected cells and remains a first-line agent for seasonal influenza.

Question 1

Which of the following infectious diseases has the highest proportion of asymptomatic chronic carriers?

Accepted Answer

Hepatitis B

Answer

Measles

Answer

Rabies

Answer

Diphtheria

Question 2

Which of the following statements about influenza infectivity is correct?

Accepted Answer

All of the options are correct.

Answer

Communicable period is 1 day before to 5-7 days after the onset of symptoms

Answer

There can be subclinical cases of influenza.

Answer

The primary source of infection is a clinical case.

Question 3

Vaccine derived polio virus outbreaks are due to?

Accepted Answer

Type-2 poliovirus

Answer

Type-3 poliovirus

Answer

Type-1 poliovirus

Answer

All types of poliovirus

Question 4

Which of the following statements regarding polio vaccination is false?

Accepted Answer

First OPV is given at 4 weeks

Answer

OPV induces both humoral and intestinal immunity

Answer

IPV is given intramuscularly

Answer

Both killed and live vaccines are available

Question 5

Reservoir of infection in enteric fever?

Accepted Answer

Man

Answer

Birds

Answer

Cow

Answer

Water

Question 6

What is the Hib conjugate vaccine made of?

Accepted Answer

Capsular polysaccharide with carrier

Answer

Capsular polysaccharide

Answer

Purified protein with carrier

Answer

Cell wall polysaccharide

Question 7

What is a common characteristic of the H5N1 and H7N7 strains of influenza?

Accepted Answer

Strains of avian influenza

Answer

Frequent endemic infection in man

Answer

Have same frequency of antigenic variation

Answer

None of the options

Question 8

Capsular polysaccharide derived vaccine is available for all meningococci except?

Accepted Answer

Group B

Answer

Group C

Answer

Group Y

Answer

Group A

Question 9

Which of the following statements regarding Pertussis is INCORRECT?

Accepted Answer

Cerebellar ataxia is a known complication.

Answer

The drug of choice is Erythromycin.

Answer

Some infections may be subclinical.

Answer

The most infective stage is the catarrhal stage.

Question 10

Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?

Accepted Answer

Acyclovir

Answer

Amantadine

Answer

Rimantadine

Answer

Oseltamivir

NEET-PG 2015

Community Medicine

Microbiology

Pediatrics

Pharmacology