Which demographic tends to have the highest risk of paralysis per poliovirus infection?

• A. Older children and adults have a higher risk of paralysis per infection than young children, though most infections occur in children under 5
• B. Infants have the highest risk
• C. Children aged 5-10 have the highest risk
• D. Adults over 60 have the highest risk

Answer: (A)

The main idea is that the chance of paralysis once infected with poliovirus increases with age. While most poliovirus infections happen in young children, the likelihood that an infection will progress to paralytic poliomyelitis is greater in older children and adults. In other words, younger kids tend to have milder or no symptoms when infected, but if paralysis develops, it’s more likely to occur in those who are older. This age-related difference in risk per infection is why the statement that older children and adults have the highest risk of paralysis per infection fits best, even though the overall number of infections is highest among young children.