Infections with A(H1N1)2009 influenza virus in Poland during the last pandemic: experience of the National Influenza Center.

This study presents epidemiological and clinical data on non-sentinel patients considered by physicians as suspected to be infected with pandemic A(H1N1)2009 virus, from whom clinical specimens were sent for testing to the National Influenza Center, NIPH-NIH in Warsaw, Poland. Between April 28, 2009 and August 10, 2010, 988 (15.7%) out of the 6,311 specimens were tested by the National Influenza Center, including 798 from non-sentinel sources and 190 from sentinel influenza surveillance network. The non-sentinel specimens were tested by conventional RT-PCR to detect influenza A and in the case of positive specimens - one-step real-time RT-PCR to detect the pandemic virus A(H1N1)2009. In 145 (18.2%) cases, infections with the pandemic virus were confirmed, with the highest number in patients aged 15-25. In 45% of the confirmed cases, a history of travel to other countries was registered. The most common symptoms were fever ≥38°C (72.7%), cough (50%), sore throat, and myalgia (26.1%). In 40.7% of the swabbed patients, clinical and epidemiological criteria for the novel influenza A(H1N1)2009, set by the European Commission, were met. There were, however, specimens from persons without any reasonable indication for testing for the pandemic virus, specimens collected incorrectly, and documentation without basic information. These weaknesses resulted in unnecessary costs and overload of health care units. An improvement should be achieved in the area of communication between different pandemic players in the future. More attention is also needed to ensure that requirements and recommendations are known and used.