Which of the following diseases is capable of infecting others before the onset of the illness?

DSSSB - 28 August 2019 (Shift-1)

Microbiology

Easy

Appeared in: DSSSB - 28 August 2019 (Shift-1)

Explanation

Mumps is a contagious viral disease caused by the mumps virus.
The period of communicability (when a person is infectious) begins before symptoms are visible.
A person with mumps is typically infectious from 2-3 days before the onset of parotitis (swelling of salivary glands) until about 5 days after.
Transmission occurs through respiratory droplets, direct contact, or fomites contaminated with saliva, making it easy to spread in close-contact settings.
The ability to spread the virus before feeling sick is a key feature that contributes to outbreaks.

Option B: Typhoid fever is caused by the bacterium Salmonella Typhi and is spread through the fecal-oral route. A person is infectious as long as they are shedding the bacteria in their feces, which typically starts with the onset of illness and can continue long after recovery in chronic carriers. It is not known to be infectious before symptoms appear.
Option C: Tuberculosis (TB) is infectious only in its active pulmonary form, when the infected person is symptomatic (e.g., coughing) and releasing bacteria into the air. Individuals with latent TB infection are not symptomatic and cannot spread the disease.
Option D: Malaria is a vector-borne disease transmitted by the bite of an infected mosquito, not directly from person to person. A person becomes infectious to a mosquito only after gametocytes (the sexual stage of the parasite) develop in their blood, which typically occurs several days after the initial symptoms of fever and chills.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Period of communicability and pre-symptomatic transmission of infectious diseases as background academic context rather than a clinical decision trigger.
Understanding pre-symptomatic transmission is critical for nurses in implementing effective infection control measures like isolation and contact tracing.
This knowledge reinforces the rationale for public health recommendations, such as vaccinating children with the MMR vaccine to prevent outbreaks of mumps, measles, and rubella.
Patient education is key. A nurse must explain to families why a person with mumps needs to be isolated even after they start feeling better, as they can still be contagious.

How to Approach the Question

First, identify the core concept of the question, which is 'pre-symptomatic transmission' – the ability to infect others before showing symptoms.
Next, systematically review the transmission characteristics of each disease listed in the options.
Recall or deduce the mode of transmission for each: Mumps (respiratory droplets), Typhoid (fecal-oral), Tuberculosis (airborne), and Malaria (vector-borne).
Consider the timing of infectivity for each disease. Viral respiratory illnesses like mumps, measles, and chickenpox are well-known for being contagious before symptoms are obvious.
Contrast this with the other options. Typhoid's infectivity is linked to shedding bacteria during illness. TB is infectious during the active, coughing phase. Malaria's infectivity to its vector occurs after the patient is already sick.
Based on this analysis, conclude that mumps is the only disease among the options that is characteristically infectious before the onset of its hallmark symptoms.

Concept Tested & Keywords

Concept Tested: Period of communicability and pre-symptomatic transmission of infectious diseases.
Stem keywords: diseases, infecting others, before the onset of the illness
Lead-in keywords: Which
Negative lead-in flag: false

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E6 Medicine Davidson Principles Practice 24e p. 131-133

E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) p. 93-95

E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart B (pp 202-403 of 604) p. 118-120