• Human parainfluenza viruses;
  • pneumonia;
  • surveillance;
  • Thailand

Background  Human parainfluenza viruses (HPIVs) are an important cause of acute respiratory illness in young children but little is known about their epidemiology in the tropics.

Methods  From 2003–2007, we conducted surveillance for hospitalized respiratory illness in rural Thailand. We performed reverse-transcriptase polymerase chain reaction on nasopharyngeal specimens and enzyme immunoassay on paired sera

Results  Of 10,097 patients enrolled, 573 (5%) of all ages and 370 (9%) of children <5 years of age had evidence of HPIV infection (HPIV1=189, HPIV2=54, HPIV3=305, untyped=27). Average adjusted annual incidence of HPIV-associated hospitalized respiratory illness was greatest in children aged <1 year (485 per 100,000 person years).

Conclusions  In Thailand, HPIV caused substantial illnesses requiring hospitalization in young children.