Concept:A viral disease is an infection caused by a virus, not by bacteria or other microorganisms.
Explanation:Measles is caused by the measles virus, which is a highly contagious RNA virus.
The virus spreads through the air when an infected person coughs, sneezes, or breathes.
It can also spread through direct contact with infected respiratory secretions.
Syphilis is a sexually transmitted infection caused by the bacterium
Treponema pallidum.
Cholera is a bacterial intestinal infection caused by the bacterium
Vibrio cholerae.
Typhoid fever is caused by the bacterium
Salmonella Typhi, which can become life-threatening without treatment.
Since syphilis, cholera, and typhoid are all bacterial diseases, they are not viral.
Measles is the only option caused by a virus.
Answer:B. Measles