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6 things to know now about coronavirus science

There's more consensus about how people are most likely to catch the virus and a growing understanding of how the virus may work.

Nearly four months since COVID-19 was declared a pandemic, our understanding of the novel coronavirus is developing and evolving.

“Almost every week, we learn something new,” said Jay Wolfson, a professor at the University of South Florida’s College of Public Health. He said the biggest thing we’ve learned is that “we don’t know a lot about it.”

Still, the growing number of infected people has provided insights into how the disease works.

Here are some things that have become clearer.

The list of people at higher risk for severe illness from COVID-19 has grown.

People older than 65 are especially vulnerable to severe illness from the virus. But younger people are also at risk of becoming seriously ill.

In late June, the U.S. Centers for Disease Control and Prevention updated its guidance to remove the 65 and older threshold, saying instead that the risk of serious illness increases steadily as people age.

The CDC also updated its list of underlying medical conditions associated with a higher likelihood of severe cases. It now says obesity, Type 2 diabetes, chronic kidney disease, serious heart conditions, sickle cell disease, chronic obstructive pulmonary disease and a weakened immune system from organ transplant can increase risk.

Based on limited data, it also said that things like asthma, pregnancy, cystic fibrosis, smoking, Type 1 diabetes, neurological conditions like dementia and high blood pressure might increase a person’s risk.

The virus acts differently and produces more symptoms than expected.

Early guidance about symptoms focused on respiratory issues like a cough or shortness of breath, but it became apparent that some infected people were experiencing other symptoms.

In April, the CDC added muscle pain, headache, sore throat and a sudden loss of taste or smell as symptoms. In May, it added gastrointestinal issues like nausea and diarrhea.

In recent months, doctors began identifying an inflammatory disease similar to Kawasaki disease in children that appeared to be linked to COVID-19. Some children have had skin rashes that appeared to be tied to the virus.

Experts have found that this virus works differently than an influenza virus and can apparently affect the cells that line blood vessels, said Dr. Sally Alrabaa, an infectious disease specialist at the University of South Florida.

“The virus seems to infect the whole body, not just the lungs,” Alrabaa said. She said the virus has been found in some instances to affect kidneys or cause blood clots that could lead to strokes.

Alrabaa said the virus is found just in the nose of many of the young and healthy people who get infected. But for a minority of people who get the virus, “it overwhelms the body.”

She said the virus does not appear to attack brain cells, but it being in the blood vessels in the circulation of the brain can cause confusion or hallucinations.

The risk of getting infected from surfaces is not as high as some originally feared.

It’s still important to wash hands and regularly clean surfaces, experts say.

But experts have been saying for months that contaminated surfaces do not seem to be the main way the virus is spreading.

“Initially, there was a lot of concern about wiping down groceries and things like that before they came into the house,” said Dr. Tara Smith, professor of epidemiology at Kent State University.

She said touching those surfaces does not seem to be a big driver of transmission.

Instead, there’s growing consensus that the main way to get infected appears to be through inhaling the virus released when an infected person coughs, sneezes or talks. That means people need to avoid extended, close person-to-person interactions, particularly indoors.

“Proximity, congestion and time are the factors that create transmission,” Wolfson said. He suggested people avoid crowded areas, particularly for prolonged periods.

There’s growing evidence that the virus could be spread through aerosols that linger in the air.

Scientists have been saying for months that the virus may be spread not only from larger respiratory droplets that are expelled when an infected person coughs or sneezes and more quickly fall to the ground but also by aerosols that can linger in the air.

The aerosols — which are simply smaller droplets that are expelled when someone talks or sings or breathes — can hang in the air longer than larger droplets and can go further than 6 feet, said Dr. Ashish Jha, director of Harvard’s Global Health Institute.

“I think there’s just plenty of evidence that aerosols are really a major source of spread,” Jha said during a media call with reporters Monday. He said washing hands and wiping down surfaces is still important. But he said masks and avoiding long durations indoors with large numbers of people need to be emphasized to reduce the chance of being infected by airborne transmission.

Jha explained that while the discussion is about droplets or aerosols, there’s actually only a gradient in terms of size. The question is more about how well the virus is able to be carried through the air and infect people.

Recently, more than 200 scientists from dozens of countries signed an open letter to the World Health Organization laying out evidence that the virus may be able to float in smaller particles and infect people more than previously thought, according to the New York Times. The World Health Organization is reviewing the scientists’ report, which urges the organization to update its guidance.

There is debate about how often the virus is infecting people through the airborne route versus larger droplets.

Smith of Kent State University said she doesn’t think that the main way the virus is spreading is through aerosols.

Still, the possibility of airborne transmission is all the more reason for people to minimize time with other people indoors, where there is less ventilation, experts say. There’s a lot of debate about what should happen in places with poorer ventilation, including some schools.

Some people who get the coronavirus see longer-term issues.

It’s too early to understand the long-term effects for people who are infected, given how short a time the virus has been around in humans.

But experts say they’re seeing more and more cases of people with lingering symptoms. Jha said he’s been concerned about lung damage on some people who have gotten the virus and survived.

Jha said he is increasingly convinced that a “sizeable minority” of people who get infected could have meaningful long-term effects.

Wolfson of USF said there’s been evidence recently that some infected people later get a condition they’ve never had before, such as cardiovascular disease or kidney disease.

“They may have that for life,” Wolfson said. He said it’s too early to know what percentage of people that happens to or why.

“We’ve only been exposed to measurements about this disease for less than six months,” Wolfson said. “We don’t have enough historical data to tell us what happens to people who had the disease three months, six months, nine months, a year afterward.”

This isn’t going away anytime soon.

As much as we’d like it, the coronavirus has not shown signs that it will just go away.

“What we’ve learned is what we’re living now in Florida,” Alrabaa said. She said as much as everyone wants to go back to “normal,” it’s important to remember that “the virus is still there. It’s circulating and it’s just waiting for this human to human transmission.”

Dozens of teams of scientists around the world are working to come up with a vaccine, but such a solution is, at best, several months away, experts say.

There have been promising findings about drugs that may help some patients with more severe symptoms, but no treatments that could cure the disease or prevent serious illness.

“We expect to have this virus with us, so we will probably have to continue to be diligent about the rate of spread,” Alrabaa said.

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