Onset and Duration of Symptoms and Timing of Disease Transmission of 2009 Influenza A (H1N1) in an Outbreak in Fukuoka, Japan, June 2009

The first confirmed case of 2009 influenza A (H IN I) in Fukuoka, Japan was reported in early-June 2009. The disease rapidly spread through this area, mainly in schools, until there were no new cases detected 3 weeks later. We describe herein the clinical characteristics of this novel infection that came to light through the investigation of this outbreak. The patient records at hospitals and local public health centers were reviewed, and we defined laboratory-confirmed cases as those of a person who had influenza-like symptoms, such as a fever of 37 degrees C or more, cough, sore throat, rhinorrhea, or headache. From May 19 to June 31, 2009, a total of 71 cases were identified. The median age was 11 years, and all the patient took neuraminidase inhibitors and fully recovered. The fevers lasted for 1 to 5 days (median, 2). Cough lasted for 2 to 11 days (median, 7), and in 10 cases (34.5%) cough started before the fever. The incubation period was 2 to 3 days. Infectors transmitted the disease to another person on the day of or the day before fever onset. The findings regarding the onset and duration of symptoms and the timing of disease transmission of 2009 influenza A (H1N1) may be useful for future response.