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The coronavirus can stay aloft for hours in tiny droplets in stagnant air, infecting people as they inhale, mounting scientific evidence suggests.

This risk is highest in crowded indoor spaces with poor ventilation, and may help explain superspreading events reported in meatpacking plants, churches and restaurants.

It’s unclear how often the virus is spread via these tiny droplets, or aerosols, compared with larger droplets that are expelled when a sick person coughs or sneezes, or transmitted through contact with contaminated surfaces, said Linsey Marr, an aerosol expert at Virginia Tech.

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Aerosols are released even when a person without symptoms exhales, talks or sings, according to Marr and more than 200 other experts, who have outlined the evidence in an open letter to the World Health Organization.

What is clear, they said, is that people should consider minimizing time indoors with people outside their families. Schools, nursing homes and businesses should consider adding powerful new air filters and ultraviolet lights that can kill airborne viruses.

What does it mean for a virus to be airborne?

For a virus to be airborne means that it can be carried through the air in a viable form. For most pathogens, this is a yes-no scenario. HIV, too delicate to survive outside the body, is not airborne. Measles is airborne, and dangerously so: It can survive in the air for up to two hours.

For the coronavirus, the definition has been more complicated. Experts agree that the virus does not travel long distances or remain viable outdoors. But evidence suggests it can traverse the length of a room and, in one set of experimental conditions, remain viable for perhaps three hours.

How are aerosols different from droplets?

Aerosols are droplets, droplets are aerosols — they do not differ except in size. Scientists sometimes refer to droplets fewer than 5 microns in diameter as aerosols. (By comparison, a red blood cell is about 5 microns in diameter; a human hair is about 50 microns wide.)

From the start of the pandemic, the WHO and other public health organizations have focused on the virus’s ability to spread through large droplets that are expelled when a symptomatic person coughs or sneezes.

These droplets are heavy, relatively speaking, and fall quickly to the floor or onto a surface that others might touch. This is why public health agencies have recommended maintaining a distance of at least 6 feet from others, and frequent hand washing.

But some experts have said for months that infected people also are releasing aerosols when they cough and sneeze. More important, they expel aerosols even when they breathe, talk or sing, especially with some exertion.

Scientists know now that people can spread the virus even in the absence of symptoms — without coughing or sneezing — and aerosols might explain that phenomenon.

Because aerosols are smaller, they contain much less virus than droplets do. But because they are lighter, they can linger in the air for hours, especially in the absence of fresh air. In a crowded indoor space, a single infected person can release enough aerosolized virus over time to infect many people, perhaps seeding a superspreader event.

For droplets to be responsible for that kind of spread, a single person would have to be within a few feet of all the other people, or to have contaminated an object that everyone else touched. All that seems unlikely to many experts: “I have to do too many mental gymnastics to explain those other routes of transmission compared to aerosol transmission, which is much simpler,” Marr said.

Can I stop worrying about physical distancing and washing my hands?

Physical distancing is still very important. The closer you are to an infected person, the more aerosols and droplets you may be exposed to. Washing your hands often is still a good idea.

What’s new is that those two things may not be enough. “We should be placing as much emphasis on masks and ventilation as we do with hand washing,” Marr said. “As far as we can tell, this is equally important, if not more important.”

Should I begin wearing a hospital-grade mask indoors? And how long is too long to stay indoors?

Health care workers may all need to wear N95 masks, which filter out most aerosols. At the moment, they are advised to do so only when engaged in certain medical procedures that are thought to produce aerosols.

For the rest of us, cloth face masks will still greatly reduce risk, as long as most people wear them. At home, when you’re with your own family or with roommates you know to be careful, masks are still not necessary. But it is a good idea to wear them in other indoor spaces, experts said.

As for how long is safe, that is frustratingly tough to answer. A lot depends on whether the room is too crowded to allow for a safe distance from others and whether there is fresh air circulating through the room.

What does airborne transmission mean for reopening schools and colleges?

This is a matter of intense debate. Many schools are poorly ventilated and are too poorly funded to invest in new filtration systems. “There is a huge vulnerability to infection transmission via aerosols in schools,” said Don Milton, an aerosol expert at the University of Maryland.

Most children younger than 12 seem to have only mild symptoms, if any, so elementary schools may get by. “So far, we don’t have evidence that elementary schools will be a problem, but the upper grades, I think, would be more likely to be a problem,” Milton said.

College dorms and classrooms are also cause for concern.

Milton said the government should think of long-term solutions for these problems. Having public schools closed “clogs up the whole economy, and it’s a major vulnerability,” he said.

“Until we understand how this is part of our national defense, and fund it appropriately, we’re going to remain extremely vulnerable to these kinds of biological threats.”

What are some things I can do to minimize the risks?

Do as much as you can outdoors. Despite the many photos of people at beaches, even a somewhat crowded beach, especially on a breezy day, is likely to be safer than a pub or an indoor restaurant with recycled air.

But even outdoors, wear a mask if you are likely to be close to others for an extended period.

When indoors, one simple thing people can do is to “open their windows and doors whenever possible,” Marr said. You can also upgrade the filters in your home air-conditioning systems, or adjust the settings to use more outdoor air rather than recirculated air.

Public buildings and businesses may want to invest in air purifiers and ultraviolet lights that can kill the virus. Despite their reputation, elevators may not be a big risk, Milton said, compared with public bathrooms or offices with stagnant air where you may spend a long time.

If none of those things are possible, try to minimize the time you spend in an indoor space, especially without a mask. The longer you spend inside, the greater the dose of virus you might inhale.

Bengaluru, Apr 1: Karnataka Health Minister B Sriramulu on Wednesday said that 200 people, out of 342 from the state who had attended the religious gathering at Markaz building in Delhi's Nizamuddin area, have been quarantined.

"200 people including four from Bengaluru and five from Belgaum, who participated in Tablighi Jamaat (in Delhi's Nizamuddin), have been quarantined. Total 342 people from Karnataka had attended the event," Sriramulu told reporters here.

The gatherings organised by the Tablighi Jamaat at the Markaz building in Nizamuddin came into the spotlight after multiple coronavirus cases were confirmed amongst those who attended the event held in March.
Twenty-four cases were reported from the national capital alone, apart from Telangana, the union territory of Andaman and Nicobar Islands amongst others.

The minister had earlier said that Bengaluru Urban and Mysuru have been identified among the prime 25 COVID-19 hotspots in the country.
Chikkaballapur, since the last fourteen days, has been emerging as another hotspot, according to Sriramulu.

The total number of coronavirus cases in India has risen to 1,637 after 240 new cases were reported in the country, according to the Ministry of Health and Family Welfare, on Wednesday.

The total number of active cases rose to 1466 in the country, while 132 people have been cured and discharged after receiving treatment, as of 9 am.

Munbai/New Delhi, May 4: India expects bad debts at its banks could double after the coronavirus crisis brought the economy to a sudden halt, a senior government official and four top bankers said.

Indian banks are already grappling with 9.35 trillion rupees ($123 billion) of soured loans, which was equivalent to about 9.1% of their total assets at the end of September 2019.

"There is a considered view in the government that bank non-performing assets (NPAs) could double to 18-20% by the end of the fiscal year, as 20-25% of outstanding loans face a risk of default," the official with direct knowledge of the matter said.

A fresh surge in bad debt could hit credit growth and delay India's recovery from the coronavirus pandemic.

"These are unprecedented times and the way it's going we can expect banks to report double the amount of NPAs from what we've seen in earlier quarters," the finance head of a top public sector bank told Reuters.

The official and bankers declined to be named as they were not officially authorized to discuss the matter with media.

India's finance ministry declined to comment, while the Reserve Bank of India and Indian Banks' Association, the main industry body, did not immediately respond to emails seeking comment.

The Indian economy has ground to a standstill amid a 40-day nationwide lockdown to rein in the spread of coronavirus cases.

The lockdown has now been extended by a further two weeks, but the government has begun to ease some restrictions in districts that are relatively unscathed by the virus.

India has so far recorded nearly 40,000 cases of the coronavirus and more than 1,300 deaths from COVID-19, the respiratory disease caused by the coronavirus.

'RIDING THE TIGER'

Bankers fear it is unlikely that the economy will fully open up before June or July, and loans, especially those to small- and medium-sized businesses which constitute nearly 20% of overall credit, may be among the worst affected.

This is because all 10 of India's largest cities fall in high-risk red zones, where restrictions will remain stringent.

A report by Axis Bank said that these red zones, which contribute significantly to India's economy, account for roughly 83% of the overall loans made by its banks as of December.

One of the sources, an executive director of a public sector bank, said that economic growth had been sluggish and risks had been heightened, even ahead of the coronavirus crisis.

"Now we have this Black Swan event which means without any meaningful government stimulus, the economy will be in tatters for several more quarters," he said.

McKinsey & Co last month forecast India's economy could contract by around 20% in the three months through June, if the lockdown was extended to mid-May, and growth in the fiscal year was likely to fall 2% to 3%.

Bankers say the only way to stem the steep rise in bad loans is if the RBI significantly relaxes bad asset recognition rules.

Banks have asked the central bank to allow all loans to be categorized as NPAs only after 180 days, which is double the current 90-day window.

"The lockdown is like riding the tiger, once we get off it we'll be in a difficult position," a senior private sector banker said.