China must admit to massive crackdown on Muslims in Xinjiang: Amnesty

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.

Madrid, Mar 26: More than three billion people around the world were living under lockdown on Wednesday as governments stepped up their efforts against the coronavirus pandemic which has left more than 20,000 people dead.

As the number of confirmed cases worldwide soared past 450,000, UN Secretary General Antonio Guterres warned that only a concerted global effort could stop the spread of the virus.

In Spain, the number of fatalities surpassed those of China, where the novel coronavirus first emerged three months ago, making it the hardest-hit nation after Italy.

A total of more than 20,800 deaths have now been reported in 182 countries and territories, according to an AFP tally.

Stock markets rebounded after the US Congress moved closer to passing a $2.2 trillion relief package to prop up a teetering US economy.

In Washington, President Donald Trump said New York, the epicenter of the US outbreak with over 30,000 cases, likely has a few "tough weeks" ahead but he would decide soon whether unaffected parts of the country can get back to work.

"We want to get our country going again," Trump said. "I'm not going to do anything rash or hastily.

"By Easter we'll have a recommendation and maybe before Easter," said Trump, who had been touting a strong US economy as he faces an election in November.

UN chief Guterres said the world needs to ban together to stem the pandemic.

"COVID-19 is threatening the whole of humanity -- and the whole of humanity must fight back," Guterres said, launching an appeal for $2 billion to help the world's poor.

"Global action and solidarity are crucial," he said. "Individual country responses are not going to be enough."

India's stay-at-home order for its 1.3 billion people is now the biggest, taking the total number of individuals facing restrictions on their daily lives to more than three billion.

Anxious Indians raced for supplies after the world's second-biggest population was ordered not to leave their houses for three weeks.

Russia, which announced the death of two patients who tested positive for coronavirus on Wednesday, is expected to follow suit.

President Vladimir Putin declared next week a public holiday and postponed a public vote on controversial constitutional reforms, urging people to follow instructions given by authorities.

In Britain, heir to the throne Prince Charles became the latest high-profile figure to be infected, though he has suffered only mild symptoms.

The G20 major economies will hold an emergency videoconference on Thursday to discuss a global response to the crisis, as will the 27 leaders of the European Union, the outbreak's new epicenter.

China has begun to relax its own draconian restrictions on free movement in the province of Hubei -- where the outbreak began in December -- after the country reported no new cases.

Crowds jammed trains and buses in the province as people took their first opportunity to travel.

But Spain saw the number of deaths surge to more than 3,400 after 738 people died in the past 24 hours and the government announced a 432-million-euro ($467 million) deal to buy medical supplies from Beijing.

The death toll in Italy jumped in 24 hours by 683 to 7,503 -- by far the highest of any country.

The number of French deaths was up by 231 on Wednesday to more than 1,330, and metro and rail services in Paris were cut to a minimum.

Spain and Italy were joined by France and six more EU countries in urging Germany and the Netherlands to allow the issue of joint European bonds to cut borrowing costs and stabilise the eurozone economy.

The call is likely to fall on deaf ears when EU leaders talk on Thursday -- with northern members wary of pooling debt with big spenders -- but they will sign off on an "unprecedented" recovery plan.

At La Paz University Hospital in Madrid, nurse Guillen del Barrio sounded bereft as he related what happened overnight.

"It is really hard, we had feverish people for many hours in the waiting room," the 30-year-old told AFP.

"Many of my colleagues were crying because there were people who are dying alone, without seeing their family for the last time."

Coronavirus cases are also spreading in the Middle East, where Iran's death toll topped 2,000, and in Africa, where Mali declared its first case and several nations announced states of emergency.

In Japan, which has postponed this year's Olympic Games, Tokyo's governor urged residents to stay home this weekend, warning of a possible "explosion" of the coronavirus.

Jerusalem's Church of the Holy Sepulchre, believed by Christians to house Christ's tomb, was shut as Israel tightened movement restrictions.

The impact of the pandemic is also hitting European football, with leagues and tournaments cancelled, while the fate of the Wimbledon tennis tournament could be decided next week.

The economic damage of the virus -- and the lockdowns -- could also be devastating, with fears of a worldwide recession worse than the financial meltdown more than a decade ago.

But financial markets rose after US leaders reached agreement on a stimulus package worth roughly 10 percent of the US economy, an injection Senate Majority Leader Mitch McConnell said represented a "wartime level of investment."

Meanwhile, more than half of all Americans have been told to stay at home, including residents of the largest state, California.

The United States has at least 65,700 cases and 942 people have died.

Up to 2,241 new cases of COVID-19 have been reported across the globe as of Thursday, bringing the total count to 95,333, according to the latest official data by the World Health Organization (WHO).

Five countries, territories and areas reported COVID-19 cases for the first time in the past 24 hours, the Xinhua news agency reported.

WHO Director-General Tedros Adhanom Ghebreyesus emphasised the importance of implementing a comprehensive approach to mitigate the impact of the virus in a briefing on Wednesday.