Hemorrhagic pneumonia by influenza virus: deaths in a low-risk group during the epidemic of dengue in Cuba

Abstract Background : In Cuba, flu is the first cause of infectious diseases and the fifth general cause of death associated with pneumonia. Lung necropsies were carried out on 15 fatal cases, between 20–54 years old, and dengue was presumptively diagnosed during an epidemic outbreak in 1997. According to virological evaluation, it was demonstrated that the causative agent in nine of these cases was influenza virus. Techniques and Methods : Indirect Immunofluorescence (IFI); immunoperoxidase staining (IPS); RT-PCR; nucleotide sequence. Culture was in MDCK cells and chicken eggs and hemagglutination inhibition was used for antigenic characterization. Results : With the IFA technique, nine cases (60%) were positive and with IPS, seven cases were positive (46.7%). In MDCK and chicken eggs, six hemagglutinating agents characterized by hemagglutination inhibition were similar to the reference strain A/Johannesburg/33/94 (H3N2). Type and subtype A(H3N2) were demonstrated by RT-PCR, too. Nucleotide sequences were determined and compared. Serological studies showed that the isolated A/Santiago de Cuba/193/97 strain was circulating in the population studied. Morbidity reports during January to May showed an average of 19 600 cases per month; however, morbidity during June and July rose to 39 800 per month. Conclusion : This is the first report about the co-circulation of influenza and dengue viruses in Cuba. It also reinforces the necessity of developing prophylactic, clinical and epidemiological actions against flu during dengue virus epidemics.