Did you know that, in addition to humans, flu can also infect chickens, pigs, dogs, ducks, cats, geese, camels, ferrets, horses, seals, and whales? Broadly speaking, viruses are made of two things, proteins and nucleic acids (nucleic acids are the stuff that genes are made of). The proteins make a coat around the genes and this coat protects them from the environment and helps the virus to infect cells. There are multiple types of flu virus and we categorize these types based on the two proteins that appear on the surface of the virus. These two proteins are called hemagglutinin and neuraminidase. These proteins are assigned a number based on their specific shape, giving us many combinations, for example H1N1 or H5N1. These different combinations of proteins on the surface of the flu virus have an important impact on which animal species the flu virus infects. For example, there is a chicken virus (H5N8) causing infections in bird populations in Europe in 2017, but this virus is unlikely to cause illness in people.

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