Community-acquired influenza C virus infection in children.

To clarify the epidemiologic and clinical features of community-acquired influenza C infection in children, we took specimens throughout the year from a larger number of patients with acute respiratory illnesses in a pediatric clinic in Yamagata, Japan. During a 2-year survey, 20 strains of influenza C virus were isolated from 13,426 specimens. These isolates were recovered throughout the year. The ages of patients with influenza C virus isolates ranged from 2 months to 11 years and peaked at the age of 1 year. The clinical diagnosis of patients with influenza C virus infection included bronchitis in one child and pneumonia in four. Community-acquired influenza C infection in children can cause a variety of respiratory illnesses that cannot be clinically differentiated from those caused by other viruses.