In an adenovirus outbreak in a NICU, attack rate among neonates is what value?

• A. 72.7%
• B. 81.8%
• C. 60%
• D. 50%

Answer: (B)

Attack rate measures the risk that someone exposed to the outbreak will develop the disease, calculated as the number of new cases among those exposed divided by the total number exposed, times 100. In a NICU adenovirus outbreak, many neonates are at risk due to close contact and shared environments, so a high attack rate reflects substantial transmission. If, for example, 9 of 11 exposed neonates became ill, the attack rate would be 9/11 = 81.8%, which matches the value given. This high rate emphasizes how contagious adenovirus can be in a NICU and highlights the need for strict infection prevention measures.