How Did The Novel Coronavirus Causing COVID-19 Infect Humans?

By Jordyn Posluns on March 7 2020 in Answer

Coronaviruses are a broad family of viruses that are characterized by their crown-like spikes (corona means crown in Latin). 
Coronaviruses are a broad family of viruses that are characterized by their crown-like spikes (corona means crown in Latin). 
  • The majority of people contract one of the milder strains of human coronaviruses at some point in their lives.
  • Researchers believe the COVID-19 outbreak began in a wet market in Wuhan, China, where live and dead animals are slaughtered and sold for human consumption.
  • Researchers still don't understand for certain how COVID-19 spread from animals to people, but believe that bats are the original source of the virus.

As of March 5th, 2020, over 95,700 cases of the new coronavirus have been recorded globally, attributing to the deaths of at least 3,200 individuals, based on findings from Johns Hopkins University.  With now more than 60 countries affected, the negative impacts of the COVID-19 outbreak - both physical and economic - are being felt by billions of people worldwide. It's been three months since the first case of the infection was identified, yet significant questions about the virus remain unanswered.  Here's what scientists do know about the virus that causes the COVID-19 disease and how it started:

Firstly, What Is A Coronavirus?

Coronaviruses are a broad family of viruses that are characterized by their crown-like spikes (corona means crown in Latin).  The majority of people contract one of the human strains of coronaviruses at some point in their lives, presenting common cold and flu symptoms like runny nose, cough, sore throat, and fever for a relatively short period of time.

Only seven types of coronaviruses, including COVID-19, are able to be contracted by people from animals, and can then spread among human populations.  The zoonosis of two deadly coronaviruses which caused the outbreaks of Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) were transmitted from dromedary camels and civet cats, respectively, to humans.  These diseases have collectively killed over 1,500 people since 2002.  According to the Centers for Disease Control and Prevention, however, many known coronaviruses that spread between animals do not infect humans.

What Is COVID-19?

Originally termed the "novel coronavirus," COVID-19 virus is a newly-identified type of coronavirus that was first isolated in December 2019.  The first cluster of infectious cases in humans was identified in Wuhan, a Chinese city with a population of 11 million.  It is important to note that the COVID-19 virus is not the same as the coronaviruses that commonly circulate among human populations, which cause mild forms of the disease, like the common cold.

Approximately 20% of confirmed cases of COVID-19 disease has been classified as "severe" or "critical," while the death rate remains around 2%, significantly lower than that of MERS (30%) and SARS (10%). Chinese scientists have reported that the virus has mutated into two unique strains, further complicating the development of a COVID-19 virus vaccine.

Where Exactly Did COVID-19 virus Come From?

Experts explain that scientists' understanding of the origin of the virus of COVID-19 still isn't perfectly clear, but researchers have uncovered several theories.  The most notable involves a "wet market" - a traditional Asian retail food market comprised of stalls that sell both live and dead seafood and other wildlife, like fish and birds - in Wuhan.  Infection transmission from animals to humans is increasingly risky in wet markets, since the markets are extremely crowded, and animals are housed and slaughtered on the market's premises, which poses a challenge to the fastidious maintenance of the market's hygienic standards.  The market is now closed to the public until further notice.

While the animal source of the outbreak has yet to be conclusively determined, the original infectious host of COVID-19 virus is understood to be bats, and while bats are not available for purchase at the Wuhan wet market, they are believed to have infected certain intermediary animals, like live chickens or pangolins, which are sold there.

Jim LeDuc, head of the Galveston National Laboratory, a high security National Biocontainment Laboratory in Texas, reported to Vox, "If you look at the genetic sequence of the virus, it’s closely related to a bat virus, about 96 percent the same."

An extensive list of zoonotic viruses can be acquired from bats, including Ebola, HIV, and rabies.

How Did The Virus Jump From Animals To Humans?

Researchers aren't yet sure of how the virus that causes COVID-19 spread from bats to people.  Some propose that humans may have consumed an infected animal, while others believe humans contracted the virus after exposure to infected animal feces or urine.

Columbia University microbiology and immunology professor Vincent Racaniello told Vox, “All we know [is] its likely distant source was bats, but we don’t know who was between bats and people.” The host of the This Week in Virology podcast continued, “It could be a direct infection [between bats and humans] as well.”

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