RESUMO
Background. Influenza pneumonia often occurs as epidemics in the Asian countries and have significant impact on the health of world population. Methods. We studied the association of rain-wetting with occurrence of pneumonia during the outbreak of the influenza A (H1N1) pdm09 virus infection. All patients admitted with community-acquired pneumonia during the period 13th September to 10th October 2010 were recruited in the present study. The diagnosis of influenza was established by realtime polymerase chain reaction (RT-PCR). The demographic data and clinical profile of the patients were recorded with a special consideration to record of possible risk factors. Results. Of the 123 patients studied, 39 (32%) patients had tested positive for influenza A (H1N1) pdm09; 12 (10%) tested positive for influenza A and remaining 72 (58%) patients were negative for influenza virus. Pattern of illness was almost identical in H1N1-positive and-negative groups. History of rain-wetting was present in 48 patients (39%) preceding the onset of illness. Getting wet in the rain was significantly higher in patients with pneumonia than control subjects [odds ratio 2.53, 95% confidence intervals (CI) 1.301 - 4.91; p=0.009)]. The number of pneumonia patients was also higher on rainy days and the numbers started declining a week later. Conclusion. More pneumonia patients are admitted during the periods of greater rainfall and rain-wetting may be an important risk factor for the occurrence of pneumonia.