Certified in Public Health (CPH) Practice Exam

Which infectious micro-organism shows symptoms in around 10% of infections?

1. Measles

2. Chickenpox

3. Poliomyelitis

4. Rabies

The correct answer is: Poliomyelitis

Poliomyelitis is the correct answer because it is estimated that approximately 90% of individuals infected with the poliovirus remain asymptomatic, meaning they do not exhibit symptoms. This characteristic makes poliomyelitis particularly insidious, as those who are infected may unknowingly transmit the virus to others. The remaining 10% of those infected may exhibit symptoms, which can range from mild flu-like signs to more severe outcomes, such as paralysis. In contrast, measles typically presents symptoms in nearly all who contract it, as does chickenpox, which is characterized by a high rate of symptomatic infections. Rabies, while also serious, has a different pattern, often presenting late in the disease process after a prolonged period of incubation, but it is not typically classified in terms of a percentage of symptomatic versus asymptomatic cases in the same way as poliomyelitis. Therefore, poliomyelitis stands out as the micro-organism where only around 10% of those infected will show noticeable symptoms.