What is a coronavirus?
FAQ on Food and COVID-19: Answers From a Nutritionist

Where did the novel coronavirus come from?

The animal kingdom is teeming with coronaviruses. They are found in cats and dogs, pigs and cattle, turkey and chickens, mice, rats, rabbits and of course, humans. Insects too.

Some of those coronviruses can cross species, such as between pigs, cats and dogs, but for the most part coronaviruses stay loyal to their original hosts. Until, of course, they become that lucky mutation.

“Usually viruses from one animal really don’t effectively transmit to other animal species or even to people,” said Dr. John Williams, chief of the division of pediatric infectious diseases at the University of Pittsburgh Medical Center Children’s Hospital of Pittsburgh.

“So usually if a virus goes from an animal to a human, it’s sort of dead end. That person gets sick but it doesn’t spread further,” said Williams, who has studied coronaviruses for decades.

Besides the newly hatched novel coronavirus, there are actually sixadditional coronaviruses that infect humans — four of them cause the common cold.

Two more can be deadly. MERS-CoV is the villian behind Middle East Respiratory Syndrome, or MERS, which has killed over 800 people worldwide since it first appeared in 2012.

SARS-CoV causes a serious form of pneumonia that can also be life-threatening. Globally, it killed 774 people between 2002 and 2004. No other cases have been reported worldwide since. {To put that into context, the death toll of the novel coronavirus since it burst on the scene in December is approaching 40,000).

The coronaviruses that cause MERS and SARS are though to have crossed from mammals to humans, where they mutated to become contagious. MERS-CoV first appeared in Jordon and Saudi Arabia in 2012 and it’s thought to have crossed over to humans from dromedary camels in Africa, the Middle East and southern Asia.

“MERS is extremely deadly, about 30% of people who are infected with MERS will die,” Williams said. “So the virus got over one of the barriers — it’s able to infect humans, grow in them and cause disease — but thankfully it really doesn’t spread well person to person, other than very, very close contacts.”

SARS has been more difficult to pin down.

Because one of the most common carriers for coronaviruses are bats, it’s thought that the virus may have started there. Then it supposedly mutated to the masked palm civet, a small cat-like mammal eaten in some parts of China. But even that theory is disputed.

“SARS caused death in about 10% of people that became infected and it did spread person to person but not super effectively,” Williams said. “There weren’t many people walking around without symptoms or with mild symptoms, who could be spreading it.

“This new virus, SARS-CoV-2, has overcome more barriers,” Williams added. “It spreads easily person to person and a lot of people can have either mild disease or they might not even have symptoms, yet they can have the virus and spread it.”

The novel coronavirus appears to have originated in bats. A study published in February found the coronavirus found in bats shared 96% of the same genetic makeup as the novel coronavirus. But it wasn’t a direct link, so the bat had to have infected another species, which then infected humans.

Early reports pointed to snakes bought at a “wet market” in China were people buy live animals to eat. A recent report of the initial cases of coronavirus in China debunks the “snake flu” theory, reporting that in 13 of the 41 early cases the infected patients had no link to the wet market.

A recent hypothesis claimed the intermediate host was the pangolin, an endangered scaly, ant-eating creature beloved for its meat and scales, which are used in traditional Chinese medicine. But critics have been skeptical, sending genetic scientists back to their labs to continue the search.

At this time, scientists don’t know where the novel coronavirus began.

“These things are more difficult than [identifying] dinosaurs, because there’s no fossil record of a virus,” Williams said. “For example, the main virus I study, human metapneumovirus, is clearly a virus that has circulated in humans for decades if not a few centuries.

“However, when you look at the genetics of the virus, its closest genetic relative is a bird virus,” he added. “So, did that virus jump to humans way back and become established? That’s what we think. But it isn’t impossible that a human virus jumped to birds and became established there.”

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