Influenza A viruses are also particularly adept at evading our immune system they have a high rate of genetic mutation, resulting in a process known as antigenic variation. All of the major influenza pandemics of the last century have been caused by influenza A viruses, the most notable being the Spanish flu pandemic of 1918 which led to the death of roughly 50 million people, one-tenth of the entire global population at the time.

On the whole, influenza A viruses are considered the biggest threat. Influenza D mainly infects cattle with no recorded human infections to date. Influenza C infections in humans are rare and are thought to cause relatively mild disease. Influenza A and B are the most common, driving yearly seasonal flu epidemics. There are seven types of influenza, four of which can infect mammals: A, B, C, and D. The breakthrough may also provide a blueprint for developing a COVID-19 vaccine that retains its efficacy in the face of new variants. If successful, it may act as a precursor to a truly universal flu vaccine, one that protects against all types and subtypes of the virus. Recently there has been some success on the road to developing a much sought-after broadly neutralizing vaccine against all influenza A viruses. Source: FLUNET (global influenza surveillance and response system (GISRS). Number of specimens positive for influenza by subtype globally, from August 2012 to August 2022. Although lockdowns and social distancing efforts aimed at curbing the spread of COVID-19 also helped put a dent in seasonal influenza epidemics, the flu is now returning with full force (Figure 1).

Influenza is one such virus, causing an estimated 1 billion cases globally every year-of these, upwards of 500,000 end up being fatal. But this doesn’t change the fact that they are as present as ever, lurking in the background. With COVID-19 on the scene, talk of other respiratory viruses has taken a backseat.

Virus cultivation in cell culture