Question

Which of the following is FALSE regarding Japanese encephalitis?

• A. During epidemics, 2 to 3 cases are seen in a village
• B. A bite from an infected mosquito is always associated with disease
• C. About 70% of patients are children below 5 years of age
• D. The overt disease to inapparent infection ratio is 1:100

Hint:

Most JE infections are silent, so which absolute claim breaks down?

Answer 1

The Correct Option is B

Step 1: Recall the epidemiology of Japanese encephalitis (JE).
JE is a zoonotic arboviral disease caused by the JE virus (a flavivirus), transmitted by Culex mosquitoes, with pigs and ardeid birds as amplifying hosts.

Step 2: Evaluate each statement.
During epidemics JE typically presents as scattered cases, with only a few cases (around 2 to 3) per village, so this statement is true.
JE predominantly affects children, with a large proportion of cases below 15 years and many below 5 years, so a high paediatric proportion is true.
The ratio of overt clinical disease to inapparent (subclinical) infection is very low, classically quoted around 1:300 to 1:1000, but options such as 1:100 are accepted as reflecting that most infections are subclinical, so this is broadly true.

Step 3: Identify the false statement.
The claim that a bite from an infected mosquito is always associated with disease is false. The overwhelming majority of infections are inapparent; only a tiny fraction of infected persons develop overt encephalitis. So a bite does not always cause disease.

Step 4: Conclusion.
The false statement is option B. This matches the printed key.