Early clinical experiences with the new influenza A (H1N1/09).

Background: Because of ongoing person-to-person transmission of the disease, the World Health Organization has declared a phase 6 pandemic alert for the new type of influenza A (H1N1/09). This means that the spread of the disease must be closely monitored.

Methods: At the Düsseldorf University Hospital, patients with flu-like symptoms and their contacts have been tested for the new type of influenza A since April 2009.

Results: The first patients that tested positive for H1N1/09 were treated on 20 May 2009. By mid-September, 3372 persons underwent PCR testing of a sample obtained by deep nasal swabbing, and the results were positive in 450 (13.3%). 379 of these 450 infections, or 84.2%, had been contracted abroad. Most patients came to the hospital with flu-like symptoms within three days of becoming ill. An analysis of the first 60 patients revealed a median core temperature of 37.8 degrees C and a mildly elevated C-reactive protein concentration. All patients were treated with oseltamivir. Most of the initially symptomatic patients were asymptomatic again within 3 days; the median duration of treatment was 5 days. The median time to the first negative deep nasal swab was 4 days. No oseltamivir resistance has been found to date in our patient collective.

Conclusion: The clinical manifestations of the new type of influenza were still mild in the patient population that we studied up to mid-September 2009. At that time, the second wave of the pandemic had not yet begun in Germany. At present, however, the number of cases acquired within the country is on the rise.