Chronology of a pandemic: the new influenza A (H1N1) in Bogota, 2009-2010

Describing the behaviour of the A H1N1/09 virus related to time, age and gender in patients having suspected infection, medical health care and laboratory diagnosis. This was a descriptive and retrospective study of patients diagnosed as having the influenza A H1N1/09 virus between April 2009 and July 2010 by the Bogotá Public Health Laboratory. The first cases of A H1N1/09 virus were confirmed since week 17, 2009; positivity increased gradually, reaching maximum expression between weeks 31-36, 2009 (43 % to 53 %) and decreased during the 37th week. The age groups most affected were 6-15 years (35.4 %) and 16-25 years (28 %) (p=0.0044); the lowest percentages were found in children aged less than 1 year (8.7 %) and people older than 65 years (7.2 %) (Chi 1.98, p=0.119). The gender ratio was similar: female (18.6 %) and male (17.6 %) (Chi 1.82, p=0.1768). There was a significant increase in influenza A cases during 2009. However, this did not alter the behaviour of the endemic respiratory syncytial virus; on the other hand, the H1N1/09 subtype replaced the seasonal virus circulating amongst the population of Bogotá, similarly affecting men and women, mainly young adults. The highest prevalence of cases occurred between August and September 2009.