Influenza A and B co-infection: a case–control study and review of the literature

Abstract

Influenza virus infection remains a major cause of morbidity and mortality during winter seasons. Bacterial and virus co-infection is a commonly described situation in these patients. However, data on co-infection by influenza A and B viruses are lacking. In this study, we present the cases of co-infection by influenza A and B viruses during the winter season of 2014-2015 in our institution. We analyzed 2759 samples from 2111 patients and found that 625 samples corresponding to 609 patients were positive for influenza A or B virus. A total of 371 patients had influenza A, 228 had influenza B, and 10 (1.6 %) had influenza A and B virus detection in the same sample. The median age of co-infected patients was 78.6 years, and only one of the co-infected patients died because of the infection. Comparison with a control group of mono-infected patients revealed that co-infection was significantly associated with nosocomial acquisition [odds ratio (OR) = 4.5, 95 % confidence interval (CI) = 1.05-19.25, p = 0.042]. However, co-infection was not associated with worse outcome, previous underlying condition, or vaccination status. Multivariate analysis revealed that co-infection was not an independent risk factor for death and that no single risk factor could predict co-infection.

Selection on non-antigenic gene segments of seasonal influenza A virus and its impact on adaptive evolution

“…Our findings that selection is likely to act upon both antigenic and non-antigenic gene segments and that reassortment can influence the rate of virus adaptive evolution have important implications for predicting future influenza strains. In particular, our study indicates that viral mutations are subjected to linkage effects within and to a somewhat lesser extent between gene segments, consistent with the conclusions of (37). As a consequence, we anticipate better forecasting can be achieved if the virus genetic background is considered as a whole, and is not just restricted to HA.…”

“…Nevertheless, the number of influenza coinfections can be estimated when viral strains involved belong to either different subtypes or types (e.g. A/H3N2 and A/H1N1 or influenza A and B viruses, respectively) (36, 37). These types of coinfection have been known to occur between 1-2% in sampled influenza A viral infections (36-38).…”

A newly developed tetraplex real‐time RT‐PCR for simultaneous screening of influenza virus types A, B, C and D

“…Information on possible co‐infections with IAV and the other influenza virus types in swine is not available; in humans, co‐infection of IAV/IBV was seen in 1.6% of a case study . This aspect was addressed by examining an additional 171 samples from 25 farms with swine acutely infected with IAV.…”

Sequential, within‐season infection with influenza A (H3N2) in a usually healthy vaccinated child

“…Cocirculation of distinct influenza types, subtypes, and strains has allowed for rare coincidental infection with more than one type or subtype of influenza . In addition, consecutive infection with influenza A and B viruses within a single season has been demonstrated .…”