Serologic diagnosis of influenza in a group of patients with acute respiratory disease by means of hemaglutination inhibition test

Abstract

The aim of this study was to determine the circulation of influenza viruses in Medellín, Colombia. We studied 15 patients and 15 controls using the hemaglutination inhibition test in order to detect seric antibody titers to influenza viruses. In 8 patients (53,3%) we found four.fold rise or decrease of titers. Five patients (62,5%) were positive for subtype A(H1 N1 ), 2 (25%) for subtype A(H3N2) and 1 (12,5%) for influenza B. Titers of 40 or higher, considered as evidence of previous infection or recent viral circulation, were as follows: 53,3% of patients and 80% of controls had these titers for subtype A(H3N2); 100% of patients and control~ for subtype A(H1 N1 ) and 6,7% of patients and 13,4% of controls for subtype B. This report suggests a major recent circulation of subtype A(H1 N1 ). Type B viruses do not seem to have circl:!lated recently, since oldest people in the study did not have serological evidence of infection with this particular subtype. In conclusion, the simultaneous circulation of both subtypes of in. fluenza A (H3N2, H1 N1 ) was shown. It would be advisable to maintain permanent surveillance of these viruses in order to apply preventive measures and the right treatment.