Asymptomatic COVID-19: Five Questions Answered
By William Petri
Blood tests that check for exposure to the coronavirus are starting to come online, and preliminary findings suggest that many people have been infected without knowing it. Even people who do eventually experience the common symptoms of COVID-19 don't start coughing and spiking fevers the moment they're infected.
William Petri is a professor of medicine and microbiology at the University of Virginia who specializes in infectious diseases. Here, he runs through what's known and what isn't about asymptomatic cases of COVID-19.
How common is it for people to contract and fight off viruses without knowing it?
In general, having an infection without any symptoms is common. Perhaps the most infamous example was Typhoid Mary, who spread typhoid fever to other people without having any symptoms herself in the early 1900s.
My colleagues and I have found that many infections are fought off by the body without the person even knowing it. For example, when we carefully followed children for infection by the parasite Cryptosporidia, one of the major causes of diarrhea, almost half of those with infections showed no symptoms at all.
In the case of the flu, estimates are that anywhere from 5 percent to 25 percent of infections occur with no symptoms.
For the most part, symptoms are actually a side effect of fighting off an infection. It takes a little time for the immune system to rally that defense, so some cases are more aptly considered presymptomatic rather than asymptomatic.
How can someone spread coronavirus if they aren’t coughing and sneezing?
Everyone is on guard against the droplets that spray out from a coronavirus patient's cough or sneeze. They're a big reason public health officials have suggested everyone should wear masks.
But the virus also spreads through normal exhalations that can carry tiny droplets containing the virus. A regular breath may spread the virus several feet or more.
Spread could also come from fomites — surfaces, such as a doorknob or a grocery cart handle, that are contaminated with the coronavirus by an infected person's touch.
What’s known about how contagious an asymptomatic person might be?
No matter what, if you've been exposed to someone with COVID-19, you should self-quarantine for the entire 14-day incubation period. Even if you feel fine, you're still at risk of spreading the coronavirus to others.
Most recently it has been shown that high levels of the virus are present in respiratory secretions during the "presymptomatic" period that can last days to more than a week prior to the fever and cough characteristic of COVID-19. This ability of the virus to be transmitted by people without symptoms is a major reason for the pandemic.
After an asymptomatic infection, would someone still have antibodies against SARS-CoV-2 in their blood?
Most people are developing antibodies after recovery from COVID-19, likely even those without symptoms. It is a reasonable assumption, from what scientists know about other coronaviruses, that those antibodies will offer some measure of protection from reinfection. But nothing is known for sure yet.
Recent serosurveys in New York City that check people's blood for antibodies against SARS-CoV-2 indicate that as many as one in five residents may have been previously infected with COVID-19. Their immune systems had fought off the coronavirus, whether they'd known they were infected or not — and many apparently didn't.
How widespread is asymptomatic COVID-19 infection?
No one knows for sure, and for the moment lots of the evidence is anecdotal.
For a small example, consider the nursing home in Washington where many residents became infected. Twenty-three tested positive. Ten of them were already sick. Ten more eventually developed symptoms. But three people who tested positive never came down with the illness.
When doctors tested 397 people staying at a homeless shelter in Boston, 36 percent came up positive for COVID-19 — and none of them had complained of any symptoms.
In the case of Japanese citizens evacuated from Wuhan, China and tested for COVID-19, fully 30 percent of those infected were aymptomatic.
An Italian pre-print study that has not yet been peer-reviewed found that 43 percent of people who tested positive for COVID-19 showed no symptoms. Of concern: The researchers found no difference in how potentially contagious those with and without symptoms were, based on how much of the virus the test found in individuals' samples.
The antibody serosurveys getting underway in different parts of the country add further evidence that a good number – possibly anywhere from around 10 percent to 40 percent — of those infected might not experience symptoms.
Asymptomatic SARS-CoV-2 infection appears to be common — and will continue to complicate efforts to get the pandemic under control.
Reposted with permission from The Conversation.
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Jean-Marc Neveu and Olivier Civil never expected to find themselves battling against disposable mask pollution.
When they founded their recycling start-up Plaxtil in 2017, it was textile waste they set their sights on. The project developed a process that turned fabrics into a new recyclable material they describe as "ecological plastic."
Mounting Piles of Waste<p>It is not only the streets of Chatellerault where pandemic pollution is piling-up, but also the world's beaches and oceans. Once there, they can take up to 450 years to degrade and disappear.</p><p>Esther Röling, co-organizer of the annual Adventure Clean Up Challenge held on Hong Kong Island, has seen this waste firsthand. In October the sports challenge pitted teams against one another in a competition to remove trash from 13 hard-to-reach coastal areas around the city.</p><p>They find tons of both disposable and reusable masks, said Röling. "You wonder how it ended up there. Was it just thrown on the ground? Or was it in a garbage bag that broke open?"</p><p>Almost 10,000 kilometers away in Antibes on the sunny French Riviera, it's a similar picture. For the past few months, divers and clean-up volunteers working with an ocean clean-up non-profit called Operation Mer Propre have been collecting an increasing number of masks found on land and in the sea.</p><p>"Since the beginning of the lockdown when we started to count, we've reached 800, 900, [and now in total] 1000 masks," said co-founder Joko Peltier. </p><p>According to <a href="https://unctad.org/news/growing-plastic-pollution-wake-covid-19-how-trade-policy-can-help" target="_blank">UN estimates</a>, up to 75% of all coronavirus-related plastic could end up as waste in oceans and landfills.</p>
The Limits of Recycling<p>Yet not all are convinced the recycling of this waste is possible on a global scale. </p><p>"What those citizen groups are doing is really beneficial but once they collect it, it should just go to a landfill or an incinerator. They shouldn't necessarily expect it to get recycled," said Jonathan Krones, an industrial ecologist and visiting assistant professor of environmental studies at Boston College.</p><p>That's because mask recycling programs like Plaxtil are few and far between and most don't have the benefit of a readily adaptable production process. </p><p>Even in countries with solid recycling infrastructure, he says, the system is designed to separate out specific types of waste like bottles or cardboard.</p><p>"I imagine that it would be technically feasible to develop a separation process to filter out masks, but there simply aren't enough of them to make that economical," he said.</p><p>Collection is a big hurdle, he adds. Since each mask only weighs a fraction of a gram and they're scattered on roads or mixed with other trash, it is difficult and costly. </p><p>"You need a lot of raw material of the right quality to make investing in the recycling technology and the recycling system worthwhile," he said.<span></span><br></p>
Hemp, Sugar Cane and Sustainable Alternatives<p>Some projects are instead addressing the material used to make masks.</p><p>French company Geochanvre have created a mask made primarily from hemp, while in Australia, researchers at the Queensland University of Technology are experimenting with a disposable product made from agricultural waste. </p><p>Biodegradable options are exciting alternatives to reduce the fossil fuels needed for the creation of plastic-based masks, said Krones, but they don't absolve the wearer from the responsibility of what happens afterwards. </p><p>Bio-based masks often need their own composing solutions, he explains, because in landfill they can produce high amounts of the greenhouse gas methane when anaerobic bacteria feeds on the organic material. Methane is known to be significantly more potent than carbon dioxide.</p><p>"I think as long as we have in our mind that we want to have disposability, we're going to have to wrestle with a variety of different sorts of environmental tradeoffs," he said, adding that reusable, fabric masks are the best option available to most people.</p><p>Precimask is developing a clear face covering with an optional visor made from hard plastic, designed to be long-lasting.<br></p><p>Air enters either side of the cheeks through a technology normally found in pool filters and car exhaust systems, said company spokeswoman Juliette Chambet.</p><p>"We wanted to make ceramic-based filters that would be washable and cleanable, which would allow them to be reused as many times as desired without having to buy a new consumable or produce waste," she said. </p><p>Ultimately, encouraging mask wearers to think about the entire lifecycle of a mask is key, explains Neveu. </p><p>"We want people who put on the masks to realize that they are also responsible for the waste, he said. "It's not inevitable that this [pandemic] will become an environmental catastrophe.</p><p><em>Reposted with permission from </em><em><a href="https://www.dw.com/en/covid-19-recycling-pollution-trash-pandemic/a-55707817" target="_blank">Deutsche Welle</a>.</em><a href="https://www.ecowatch.com/r/entryeditor/2649032193#/" target="_self"></a></p>
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