MILWAUKEE — In recent months, the scientific world has seen a steady flow of research updating what we know about the novel coronavirus, SARS-CoV-2, and how it affects humans. Because the virus is so new, researchers are still grappling with many questions about its function. And because of the nature of the scientific process, no single study can completely answer those questions. Instead, new research is constantly challenging our understanding of the pandemic.

Here, we explore some recent studies that have shed new light on the virus. 


Restaurant infection shows 6 feet isn’t a perfect rule

We talk about the definition of a coronavirus “close contact” in deceivingly clear-cut terms: 6 feet of distance, 15 minutes of time. But a study out of South Korea, tracing a COVID-19 infection passed along in a restaurant, shows that these aren't hard and fast rules. 

The study, published in the Journal of Korean Medical Science this month, found that one person at an indoor restaurant appears to have spread the virus to two other diners — including a high school student who was more than 20 feet away, and for only five minutes.

As the Los Angeles Times reports, the research began as a contact tracing mystery: When the student tested positive in June, her city hadn’t seen a new case in two months, and she hadn’t recently traveled. 

But researchers were able to use the extensive data available to contact tracers in South Korea — including cellphone GPS data and CCTV footage — to track the infection back to the restaurant and recreate the scene.

The originally infected diner, a door-to-door saleswoman with an asymptomatic case, sat far away from the student and one other person who tested positive later on, and didn’t touch any of the same surfaces. But the air conditioner in the windowless restaurant carried the first patient’s viral droplets across the room, the authors conclude.

Because these two unlucky diners were directly facing the airflow, they were infected while others in the restaurant were spared — even people sitting at the same table.

Cases like this one show that a 6-foot barrier isn’t enough to completely protect from COVID-19, the authors write. “Additional considerations need to occur for COVID-19 prevention and control,” they say, including a focus on airflow and ventilation for indoor spaces.

Guidance from the Centers for Disease Control and Prevention lists indoor dining as a “higher risk” activity, even if tables can be spaced 6 feet apart. A CDC study from September found that positive COVID-19 patients were twice as likely to report having eaten at a restaurant.


CDC trims recommended quarantine time

If you’ve been potentially exposed to a coronavirus infection, quarantining is important because symptoms can take some time to show up — and you can be spreading the virus even if you don’t feel sick.

Recently, though, the CDC updated its guidance to shave a few days off the recommended quarantine period in certain circumstances: if you get a negative COVID-19 test or experience no symptoms.

Previously, the CDC advised that you should self-quarantine for a full 14 days after a possible exposure no matter what, since an infection can take two weeks to actually show up. 

Since earlier this month, the CDC now says it’s OK to cut off a quarantine after 10 days “if no symptoms have been reported during daily monitoring.” That time can be cut down to just one week if you have no symptoms and also get a negative diagnostic test on day six or seven of your quarantine.

There’s still some risk in stopping short of the full 14 days: The CDC estimates that a 10-day quarantine leaves about a 1% transmission risk, and a seven-day quarantine leaves about a 5% risk.

But CDC officials hope that offering these shortened options can decrease the burden of following health guidelines and get more people to comply with the most important chunk of self-quarantine.

"Shortening the recommended quarantine period is an important, pragmatic move,” Jennifer Nuzzo of the Johns Hopkins Center for Health Security told NPR. “It allows health officials to focus their efforts on the period of time that people are most likely to become contagious, which will hopefully boost public compliance with quarantine recommendations.”

The Wisconsin Department of Health Services, along with other local public health departments, followed suit in updating its guidance for close contacts.


First wild animal tests positive for coronavirus

It’s not just for humans anymore: Last week, a wild mink in Utah became the first non-captive animal to show a confirmed coronavirus case.

“To our knowledge, this is the first free-ranging, native wild animal confirmed with SARS-CoV-2,” a release from the U.S. Department of Agriculture states.

The positive case was discovered as researchers were swabbing animals in the area after a nearby fur farm had faced an outbreak, according to the USDA. Samples from other wild species around the farm all tested negative.

Farms in Wisconsin, Michigan, and Oregon have also grappled with outbreaks of the virus, which have killed thousands of minks. And positive cases have been identified in other captive animal species: Tigers, lions, and snow leopards in zoos, as well as dogs and cats at home.

In Denmark, the government opted to cull all 17 million of its farmed minks after some animals appeared to spread a mutated form of the virus back to their human handlers. 

Though researchers say the mink-mutated coronavirus doesn’t appear to be more dangerous than the original strain, that kind of animal-to-human jump is a major concern. Human immune systems can be slow to deal with infections passed on by animals — like the SARS-CoV-2 virus we’re dealing with now, which scientists believe came from bats.

Of course, the new case also raises concerns about the health of the animals themselves. Though the USDA release says there’s “no evidence” that a viral outbreak is currently circulating in the wild population where they found the infected mink, experts worry that the potential impact on the natural world could be severe.

“We urge officials in every state with mink farms to take aggressive measures to ensure that this horrible disease does not decimate wildlife populations,” Lori Ann Burd of the Center for Biological Diversity told the Salt Lake Tribune.


Study suggests COVID-19 immunity may last years

It’s hard to say for sure how long coronavirus immunity will last, since, relatively speaking, the virus hasn’t been around very long. But promising research based on blood samples suggests that a strong immune response sticks around for at least half a year — and possibly much longer.

The preprint study, published online in November, found that patients who recovered from COVID-19 still showed signs of immune memory to the virus after six months. And the rate of decline in the immune response was relatively slow, indicating that the body might be able to fight off the virus for years after an initial infection.

Researchers from California and New York analyzed blood samples from 185 adults, looking at a few different weapons in the immune system’s arsenal

Antibodies — the blood proteins that fight off specific invaders, like viruses — were still pretty robust after six to eight months, according to the study, with only “modest declines.” T cells, which help the immune system destroy infected cells, also dipped slightly around four to six months, but stuck around after that.

And memory B cells — which help hold onto the instructions to produce a response if the viral invader comes back — were detected in almost all cases, and appeared to increase over the course of the first six months. 

All of these results are promising signs that the body won’t quickly forget how to fight off the SARS-CoV-2 virus, the researchers say.

“That amount of memory would likely prevent the vast majority of people from getting hospitalized (from the) disease, severe disease, for many years,” co-lead author Shane Crotty, a virologist at the La Jolla Institute of Immunology, told The New York Times.

Only time can tell for sure how long immunity lasts, experts concede. And there were some variations in antibody and cell levels between different patients, indicating that not all immune responses are created equal.

Still, the study is another piece of evidence that immunity doesn’t disappear as quickly as some had initially feared. That’s good news not just for the tens of millions of COVID-19 survivors across the world, but also for those high-priority groups who are starting to get their vaccines this week​.

“The significant take home message is that the immune response to the virus is more long-lived than previously thought,” University of Warwick professor Lawrence Young wrote in a Science Media Centre statement. “This lets us continue to hold hope that an effective vaccine will be able to induce sustained protective immunity.”


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