Virus Influenza circulantes en Costa Rica 1998-2001

the objective of this study was to identify the influenza virus strains circulating in costa rica and determine the months of the year where the highest incidence is present to be able to decide when to vaccinate and which vaccine to use. nasopharyngeal aspirates and nasal washings were analyzed by inmunofluorescence from samples of children admitted to the national children hospital with acute respiratory illness. positive samples for influenza viruses were inoculated in mdck cell monolayers using trypsin in the media. isolates were typed by the hemagglutination inhibition test and sent to cdc for further testing. influenza virus can be isolated all year around but peaks during the second and third trimester. the strain alsydney/05/97 circulated during three consecutive years, appearing the strain alpanama/2007/99-like h3n2 in 2001. a/bayern/07/95-like h1n1 was detected in 1999 and the a/newcaledonia/20/99 in the year 2000. this is the first study done in costa rica, its results have been very useful to the health officials and it could be very beneficial for the rest of the central american countries.