All of the following diseases caused by viruses, except?

NORCET 2 -2021 (Shift-2)

Applied Microbiology & Infection control

Easy

Appeared in: NORCET 2 -2021 (Shift-2)

Explanation

Scrub typhus is the correct answer as it is a rickettsial disease, caused by a type of bacteria, not a virus.
The causative agent is the bacterium Orientia tsutsugamushi.
It is transmitted to humans through the bites of infected chiggers (larval mites), often resulting in a characteristic black eschar at the bite site.

Option A: Zika is a viral disease caused by the Zika virus, which belongs to the Flaviviridae family.
Option B: Japanese encephalitis is a viral disease caused by the Japanese encephalitis virus, another member of the Flaviviridae family.
Option D: Dengue is a viral disease caused by the Dengue virus (DENV), also a flavivirus.

Visual 1: Table: Comparison of Zika, Japanese Encephalitis, Scrub Typhus, and Dengue - A table comparing the causative agent, type of organism (virus/bacteria), and transmission vector for each disease.
Visual 2: Infographic: Life cycle of Orientia tsutsugamushi - Showing transmission from chigger mites to humans.
Visual 3: Map: Geographical distribution of the four diseases, highlighting overlapping endemic areas.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of infectious diseases based on causative microorganisms as background academic context rather than a clinical decision trigger.
Differentiating between viral and bacterial infections is crucial for appropriate treatment. Viral infections are generally managed with supportive care, while bacterial infections like Scrub typhus require specific antibiotics (e.g., doxycycline or azithromycin).
Misdiagnosing a bacterial infection as viral can lead to delayed antibiotic treatment, increasing the risk of severe complications like pneumonitis, meningoencephalitis, and multi-organ failure, which can be fatal.
What if? If a patient presents with fever, rash, and headache after trekking in a rural area of Southeast Asia, a differential diagnosis must include all these diseases. A history of a mite bite or the presence of a painless black scab (eschar) would strongly suggest scrub typhus, prompting the clinician to start empirical antibiotics while awaiting confirmatory test results.

How to Approach the Question

First, identify the core task of the question. The question asks you to find the disease that is NOT caused by a virus.
The keyword 'EXCEPT' is critical. This signals that three of the options will share a common characteristic (being viral diseases), and one will be the outlier.
Systematically review each option: Zika, Japanese encephalitis, Scrub typhus, and Dengue.
Access your knowledge about the causative agents for each disease.
Recall that Zika, Japanese encephalitis, and Dengue are all well-known viral infections, often grouped as arboviruses and belonging to the Flavivirus family.
Identify Scrub typhus as a rickettsial disease. Rickettsiae are a specialized group of bacteria.

Concept Tested & Keywords

Concept Tested: Classification of infectious diseases based on causative microorganisms.
Stem keywords: diseases, viruses, except
Lead-in keywords: except
Negative lead-in flag: The question uses the word 'except', asking you to find the option that does not fit the category (viral diseases).

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