Hospitalization due to human parainfluenza virus-associated lower respiratory tract illness in rural 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.