Cluster Infection of Novel Influenza A (H1N1) Virus in the Psychiatric Wards of a Hospital in Hualian County of Taiwan, 2011

Jen-Hsin Wang1, Jiunn-Shyan Julian Wu1,Ching-Fen Ko1, Yeong-Sheng Lee2, Hsiao-Ju Sun3, Hsiang-Ming Hsu4

2011 Vol.27 NO.24

Correspondence Author: Jen-Hsin Wang


In late February, 2011, thirty-seven residents with symptoms of upper respiratory infection (URI) in the psychiatric wards of a hospital in Hualian County were reported. Specimens were taken from ten of the thirty-seven cases, and eight of which were confirmed positive for novel influenza A (H1N1) virus. Since it occurred in a populous institution, the outbreak was classified as a nosocomial cluster caused by novel influenza A (H1N1) virus infection. Thirty-two percent (37/117) of the residents in the psychiatric wards have experienced URI symptoms. The investigation shows that 99.1% of the 117 residents had received 2010-2011 seasonal influenza vaccine (containing strain of A/California/7/2009 (H1N1)-like virus,) but the cluster infection of novel influenza A (H1N1) virus still occurred among them, and was therefore considered an unusual event. This study shows that although residents and workers in populous institutions are the priority objects for seasonal influenza vaccine in Taiwan and have very high vaccination coverage rates, it is still possible for cluster infection of novel influenza A (H1N1) virus to occur under an environment where residents are cared in a concentrated area. Therefore, besides from the fact that residents in a populous institution should maintain a very high vaccination coverage rate, epidemic surveillance and case notification should be improved, infection control measures should be enforced, and the vaccination coverage rate of the workers should be increased to avoid recurrence of the similar cluster infection.