| Background : |
The influenza A viruses are negative-sense, single-stranded, segmented RNA viruses of the genus Alphainfluenzavirus, family Orthomyxoviridae. There are several subtypes, named according to the type of Haemagglutinin (H1-18) and Neuraminidase (N1-11) (Centers for Disease Control and Prevention, 2017). Humans are generally infected by influenza viruses of the subtypes H1, H2 or H3, and N1 or N2. Influenza A virus subtype H3N2 (A/H3N2) is a subtype of viruses that causes influenza (flu) and can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains and in years in which it is the predominant strain, there are usually more hospitalizations. The Hong Kong flu was the first known outbreak of the H3N2 strain, and the 1968- 1969 pandemic killed an estimated one million people worldwide (CDC, 2019) WHO convenes technical consultations in February and September each year to recommend viruses for inclusion in influenza vaccines for the northern and southern hemisphere influenza seasons, respectively. Flu vaccines are based on predicting which mutants of H1N1, H3N2, H1N2, and influenza B will proliferate in the next season. Separate vaccines are developed for the Northern and Southern Hemispheres in preparation for their annual epidemics. Over the last decade, H3N2 has tended to dominate in prevalence over H1N1, H1N2, and influenza B. WHO has identified four strains as the most likely to circulate in the 2020-2021 influenza season, including Influenza A/Hong Kong/45/2019 (H3N2)-like virus. Since December, 2019, coronavirus disease 2019 (COVID-19) has been an international public health emergency and co-infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses have been reported, complicating their diagnosis (Azekawa et al., 2020; Cuadrado-Payán et al., 2020; Wu et al., 2020). |
