What is the approximate nasopharyngeal carriage rate of Streptococcus pneumoniae among healthy individuals?

• A. 5%
• B. 10%
• C. 70%
• D. 90%

Answer: (C)

Carriage of Streptococcus pneumoniae in the nasopharynx is a common, asymptomatic situation in healthy individuals, especially in young children. Being a carriage carrier means the bacteria are present without causing illness, but this state serves as a reservoir for transmission and can lead to disease in some cases.

Because transmission is high among children and those in close contact settings, carriage rates in healthy pediatric populations are very high, often around half to two-thirds of individuals, with many studies reporting about 70% in certain groups. In adults, the rate tends to be much lower, typically around 5–10%.

So, the approximate carriage rate being around 70% reflects the high prevalence seen in healthy children and certain communities, whereas much lower rates would be expected if looking at adults or broader populations.