Explainer: how coronaviruses spread from animals to humans

NEW YORK — The WHO reports the COVID-19 outbreak as of February 25 has infected 80,000 people and resulted in about 2,700 deaths, mostly in China's Hubei.

Writing in a column for Quanta Magazine, U.S. epidemiologist Tara C. Smith says that SARS-CoV-2 probably transmitted from bats to pangolins to humans.

However, Smith, who is a public health professor at Kent State, notes other coronaviruses are known to jump the species barrier.

SARS-CoV, which caused the SARS outbreak in 2003, originated from a civet cat. A decade later, MERS-CoV would emerge from a camel to infect humans.

Coronaviruses rely on surface glycoproteins for binding themselves with the receptors on the cells of their hosts to cause infections.

The part of the protein that binds is called the S1 subunit. Coronaviruses possess highly varied S1s that allow them to bind with many mammalian cell receptors, including those found on the surface of human air passageways.