Can people spread coronavirus after they recover?


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Can people spread coronavirus after they recover?

Low-level viruses

It is not uncommon for viruses to persist at low levels in the body even after someone recovers from an illness, said Ebenezer Tumban, a virologist at Michigan Tech University. For example, Zika virus and Ebola virus are known to stick around for months after patients recover, Johnson noted.

The test that the four patients from Wuhan, China, underwent looks for genetic fragments of the virus in the body, Tumban said. The Tamiflu they were taking could have pushed the number of viral copies in their bodies down to just a few, he said. At that point, the test would not have been sensitive enough to detect the virus.

After the antiviral treatment ended, the viruses may have begun replicating again at a low level, Tumban said. There would not have been enough of the virus to cause tissue damage, so the patients felt no symptoms. But the number of viral copies would have gotten high enough for the test to catch them again.

At that point, the individuals were likely not very contagious, Johnson said. Coughing and sneezing spews viral particles around, but these individuals were not coughing or sneezing. Their viral loads were also low. It would take more intimate contact to spread the virus.

“They should be careful in the household setting not to share drinks and make sure they’re washing their hands frequently,” she said. “But if they’re just a carrier, they shouldn’t be able to transmit outside of that close contact of shared beverage and food.”

Immunity implications

None of the study patients’ family members tested positive for coronavirus at the time of the paper’s publication. However, the authors noted that the patients were all medical professionals who took very careful precautions to avoid spreading the disease while at home.

Virus that persists in the body may elicit enough of an immune response to provide some protection against new infection, Johnson said. There are many questions about how long immunity would last, though, Tumban said. For example, the body maintains immunity against the coronaviruses that cause the common cold for only a year or two, he said. And there is always the possibility that the new coronavirus would mutate as it moves through populations, changing into a version that already-exposed immune systems can’t recognize.

“The challenge is, how fast does this mutate?” Johnson said.

More follow-up studies are needed to understand recovery from COVID-19, Johnson said. The individuals in the study from Wuhan were all of similar age and health status, and none experienced severe illness from COVID-19.

Future research should also look at viral loads within the lungs, Tumban said. A throat swab captures the virus only from the upper reaches of the respiratory tract, but the virus makes its home deep in the lungs. Sampling from the lungs is a more invasive procedure, involving washing fluid through the alveoli (small air sacs in the lungs) and testing that fluid for viral particles, Tumban said. Still, the study suggests that long-term monitoring of recovered patients and their contacts is important.

“One week or two weeks after, is the amount of virus in the blood or lungs going to come up to a higher concentration so that the person can transmit it to other people?” Tumban said. “That’s something that we still don’t know.”

 

Originally published on Live Science.

Here’s how long the coronavirus will last on surfaces, and how to disinfect those surfaces.


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Here’s how long the coronavirus will last on surfaces, and how to disinfect those surfaces.

Scientists figure out how new coronavirus breaks into human cells


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Scientists figure out how new coronavirus breaks into human cells

Zhou and his team used a tool called cryo electron microscopy, which employs deeply frozen samples and electron beams to image the tiniest structures of biological molecules. The researchers found that the molecular bond between SARS-CoV-2’s spike protein and ACE2 looks fairly similar to the binding pattern of the coronavirus that caused the outbreak of SARS in 2003. There are some differences, however, in the precise amino acids used to bind SARS-CoV-2 to that ACE2 receptor compared with the virus that causes SARS (severe acute respiratory syndrome), the researchers said.

“While some might consider the differences subtle,” Gallagher said, “they might be meaningful with respect to the strength with which each of those viruses stick.”

That “stickiness” could affect how easily a virus transmits from one person to another. If any given viral particle is more likely to enter a cell once it enters the human body, transmission of disease is more likely.

There are other coronaviruses that circulate regularly, causing upper respiratory infections that most people think of as the common cold. Those coronaviruses don’t interact with the ACE2 receptor, Gallagher said, but rather, they get into the body using other receptors on human cells.

Coronavirus structure implications

The structure of SARS-CoV-2’s “key” and the body’s “lock” could theoretically provide a target for antiviral drugs that would stop the new coronavirus from getting into new cells. Most antiviral drugs already on the market focus on halting viral replication within the cell, so a drug that targeted viral entry would be new territory, Gallagher said.

“There is no effective clinical drug that will block that interaction that I know of” that’s already in use, he said.

The viral spike protein is also a promising target for vaccines, because it’s the part of the virus that interacts with its environment and so could be easily recognized by the immune system, Gallagher said.

Even so, developing either drugs or a vaccine will be a challenging task. Treatments and vaccines not only have to prove effective against the virus, but must also be safe for people, Gallagher said. U.S. Centers for Disease Control and Prevention officials have said that the earliest a coronavirus vaccine could be available is in a year to a year and a half.

Originally published on Live Science.

‘Rapunzel Syndrome’ Caused Woman’s Odd Symptoms


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‘Rapunzel Syndrome’ Caused Woman’s Odd Symptoms

Man in China Contracts Brain Parasite After Eating Hot Pot


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Man in China Contracts Brain Parasite After Eating Hot Pot

How one small Italian town cut coronavirus cases to zero in just a few weeks


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How one small Italian town cut coronavirus cases to zero in just a few weeks

The coronavirus did not escape from a lab. Here’s how we know.


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The coronavirus did not escape from a lab. Here’s how we know.