The Spanish flu of 1918 remains the worst flu pandemic on record, but there have been several milder ones since (see chart, below). A pandemic is a global epidemic and, in theory, flu does that every year in the northern and southern winters. But with flu, the term is reserved for when an influenza A virus emerges that isn’t just a slightly mutated version of last winter’s flu, but a complete novelty, with surface proteins most people have no immunity to.
Novel viruses are constantly evolving in the birds, pigs and other animals that also carry influenza A, and they can shuffle their genes with human strains, or just adapt to mammals directly. Virologists consider flu pandemics inevitable. The World Bank says a bad one “
Published at Thu, 04 Jan 2018 14:00:00 +0000