11 critical questions about the coronavirus that remain unanswered, 6 months after the first cases were reported

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• Experts continue to study the coronavirus as the number of people it infects and kills rises each day.
• Scientists are increasingly certain the coronavirus came from bats but aren't sure exactly how it hopped over to humans.
• Researchers also don't yet know why the virus doesn't cause symptoms in most children or how long people with antibodies might be immune.
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In the realm of medicine, what you don't know can indeed kill you.

Six months have passed since China reported the first coronavirus cases to the World Health Organization. But evn now, what experts are still trying to understand sometimes seems to outweigh what they can say for certain.

That is little surprise to any infectious-disease researcher: Highly contagious diseases can move through communities much more quickly than the methodical pace of science can produce vital answers.

What we do know is that the coronavirus seems to have emerged in China as early as mid-November and has now reached 188 countries, infected more than 10.4 million people, and killed around 510,000. Population-level studies using new testing could boost case numbers about 10-fold in the US and perhaps elsewhere as well.

As hospitals around the world care for COVID-19 patients with blood clots, strokes, and long-lasting respiratory failure, scientists are racing to study the coronavirus, spread life-saving information, and combat dangerous misunderstandings.

Here are 11 of the biggest questions surrounding the coronavirus and COVID-19, and why answering each one is critically important.

How did the new coronavirus get into people?

Themba Hadebe/AP Photo

The first coronavirus infections was thought to have emerged in a wet market in Wuhan, in China's Hubei province. But newer research suggests the market may simply have been a major spreading site.

Researchers are fairly certain that the virus — a spiky ball roughly the size of a smoke particle — developed in bats. Lab tests show that it shares roughly 80% of its 30,000-letter genome with SARS (severe acute respiratory syndrome), a virus that also came from bats and triggered an epidemic in 2002 and 2003. It also shares about 96% of its genome with other coronaviruses in bats.

Mounting evidence continues to undercut the conspiracy theory that the virus came from a Chinese laboratory.

Still, researchers still aren't sure how the coronavirus made the jump from bats to humans. In the case of SARS, the weasel-like civet became an intermediate animal host. Researchers have suggested that civets, pigs, snakes, or possibly pangolins — scaly nocturnal mammals often poached for the keratin in their scales — were an intermediary host for the new coronavirus. But it could also be that the virus jumped straight from bats to humans.

A May study suggested that SARS-CoV-2 (the virus' clinical name) may be a hybrid of bat and pangolin viruses.

Why it matters: Understanding how novel zoonotic diseases evolve and spread could lead to improved tracing of and treatments for new emerging diseases.

How many people have actually gotten COVID-19?

Jim Urquhart/Reuters

Global tallies of cases, deaths, recoveries, and active infections reflect only the confirmed numbers — researchers suspect the actual number of cases is far, far larger.

For every person who tests positive for the novel coronavirus, there may be about 10 undetected cases. This is because testing capacity lags behind the pace of the disease, and many governments, including in the US, failed to implement widespread testing early on.

New estimates from MIT suggest the world had already seen 249 million coronavirus cases and 1.75 million deaths by June 18. That would make the global case total 12 times higher than official reports, and the global death toll 1.5 times higher.

Other similar research estimated that the US alone may have seen 8.7 million coronavirus cases from March 8 to 28. US researchers also suggested in May that the nation's official death count may "substantially understate" the actual number of coronavirus fatalities.

Meanwhile, Italian studies suggest that Italy's coronavirus deaths could be twice as high as the official tally.

Why it matters: An accurate assessment is critical in helping researchers better understand the coronavirus' spread, COVID-19's mortality rate, the prevalence of asymptomatic carriers, and other factors. It would also give scientists a more accurate picture of the effects of social distancing, lockdowns, contact tracing, and quarantining.

What makes the coronavirus so good at spreading?

Indonesian Foreign Ministry via AP

Viruses are small, streamlined particles that have evolved to make many, many copies of themselves by hijacking living cells of a host.

The measurement of a virus' ability to spread from one person to another is called R0, or R-naught. The higher the value, the greater the contagiousness — though it varies by region and setting. The novel coronavirus' average R0 is roughly 2.2, meaning one infected person, on average, spreads it to 2.2 people. But it had a whopping R0 of 5.7 in some densely populated regions early in the pandemic.

The seasonal flu, by contrast, has an R0 of about 1.3.

A person's ability to transmit the virus depends partly on their viral load: the amount of virus particles they release into the environment. Coronavirus patients tend to have high viral loads in the throat, nasal cavity, and upper respiratory tract, which makes the virus highly contagious. Research indicates that there's little difference in the viral loads between coronavirus patients who show symptoms and those who don't.

Coughing — a signature symptom of COVID-19 — helps spread viruses in tiny droplets, especially in confined spaces. But the virus can also spread through singing, normal breathing, or even loud conversation.

Just one minute of loud speech can produce over 1,000 coronavirus-containing droplets that linger in the air for eight minutes or longer, according to research from the National Institutes of Health. Studies have shown that just a few hundred copies of a respiratory virus are enough to infect another person.

There's also evidence the virus may be spread by feces, but that seems to pose less of a transmission threat. 

Why it matters: Knowing how a virus gets around can help everyone better prevent its spread. Getting a handle on its behavior may also spur governments to act sooner to contain future outbreaks of this or other similar diseases.

See the rest of the story at Business Insider

See Also:

• An interactive map of the US cities and states still under lockdown — and those that are reopening
• 'It's hard to pay off your medical school loans in this kind of a job': Doctors who can protect the world against pandemics are in short supply
• America's biggest health insurers have been so profitable during the coronavirus that one is already giving cash back to customers, while hospitals lose billions

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