In Norway, investigators examined apparently healthy children in daycare to determine which viruses indicate disease and which do not.

A total of 161 children participated in the study. Mucus samples were taken while the children were in childcare during four fall and winter visits. The children were also clinically evaluated by a pediatrician, who listened to their lungs and checked their throat and ears. Close to 80% of all the children from the two participating daycares participated in the study.

Analyses of the mucus samples showed that 43% of the children had one or more viruses in their respiratory tract.

The clinical examination showed that 24% had obvious signs of respiratory infection, with red swollen throats and red inflamed eardrums. Another 41% had milder signs of respiratory infection, with stuffy noses and slightly affected eardrums.

Only one in three children showed no signs of respiratory infection at all.

Among the children with clear signs of respiratory infection, 70% had one or more viruses in their respiratory tract. Even among children with no signs of respiratory infection, 30% had viruses.

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