Clinical characteristics of children with influenza A virus infection requiring hospitalization.

From September 1997 to March 2002, a total of 84 children were admitted to Chang Gung Children's Hospital due to influenza A virus infection. Influenza A virus infection was documented in 61 cases by viral isolation from throat and in 23 cases by serologic studies. The mean age of patients was 43.8 months, ranging from 20 days to 16 years. Forty-one (49%) patients were male. Lower respiratory tract infection (53 of 84 cases) was the most common clinical manifestation, occurring predominantly in children younger than 5 years (49 of 53 cases). The types of lower respiratory tract infection included bronchiolitis/bronchopneumonia in 33 cases, pneumonia in 17, and croup in 3. Central nervous system dysfunction was noted in 26 patients, predominantly in older children (18 of 26 cases). This included encephalopathy in 11 cases, encephalitis in 10, aseptic meningitis in 2, psychosis in 1, febrile convulsions in 1, and acute disseminated encephalomyelitis in 1. Gastrointestinal symptoms were mild in most patients. Diarrhea occurred in 18.4% of the children younger than 5 years, compared with only 8.4% of the older children. By contrast, abdominal pain was more common in older children (16.7%) than in younger children (6.7%). Ten children had leukocytosis (white blood cell > or = 15000 /microL) and 9 of them were younger than 5 years. Eleven children had a C-reactive protein level greater than 100 mg/L and 10 of them were younger than 5 years. The mean duration of fever and hospitalization were 4.6 +/- 2.8 days and 7.4 +/- 5.7 days, respectively. The clinical outcomes were excellent in all but 1 patient who died from intractable pulmonary hemorrhage. The frequency and duration of hospitalization due to influenza A virus is much greater than generally thought in Taiwan, suggesting an urgent need for educational programs to increase awareness of the characteristics and risks for this illness.