Orbit of Chandrayaan-2’s lander lowered, one step closer to Moon landing

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.

Follow latest updates on the Covid-19 pandemic here

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.

New Delhi, Feb 4: Senior BJP leader and Defence Minister Rajnath Singh on Monday accused Delhi's ruling Aam Aadmi Party of not implementing the central government's schemes in the national capital.

Addressing an election rally in Moti Bagh, he also sought to allay fears over the Citizenship Amendment Act (CAA), assuring the gathering that the legislation will not take away anyone's citizenship.

Singh alleged that the Chief Minister Arvind Kejriwal-led Delhi government did not do anything in the last five years.

The AAP had promised to add 5,000 buses to the fleet of the Delhi Transport Corporation (DTC), but instead the number has come down by 1,000, he claimed.

The Union minister said the AAP dispensation did not implement central schemes in Delhi fearing that the popularity of the Prime Minister Narendra Modi-led government will grow among Delhiites.

Pension schemes and the Centre's flagship health insurance scheme, Ayushman Bharat Yojana, are some of those that the Kejriwal government did not allow to be implemented in Delhi.

On the anti-CAA protests, Singh said that the opposition parties have been spreading "lies" about amended citizenship law and the National Population Register (NPR).

"The CAA will not take away anyone's citizenship. The opposition parties are spreading lies about the CAA. There should be no such politics over this. Some people are trying to write the history of the country with the ink of hatred," he said.

The culture of India is such that it considers the entire world one family, he said.

Delhi goes to polls on February 8. The results will be declared on February 11.

Dubai, Jan 8: A Ukrainian airliner crashed soon after taking off from Tehran's Imam Khomeini airport on Wednesday, killing all 176 people aboard, Iran's state television and Ukraine's leaders said.

The Boeing 737 belonging to Ukraine International Airlines crashed near the airport and burst into flames. Ukraine's embassy in Iran, citing preliminary information, said the plane had suffered engine failure and the crash was not caused by "terrorism".

Ukraine President Volodymyr Zelenskiy said there were no survivors.

"My sincere condolences to the relatives and friends of all passengers and crew," Zelenskiy said in a statement, adding that Ukraine was seeking to establish the circumstances of the crash and the death toll.

Iranian TV said the crash was due to technical problems but did not elaborate. State broadcaster IRIB said on its website that one of the plane's two black boxes - the flight data recorder and the cockpit voice recorder - had been found.

Iranian media quoted an Iranian aviation official as saying the pilot of the airliner did not declare an emergency.

There was no official word from Ukraine International Airlines. It was the Kiev-based airline's first fatal crash.

"The fire is so heavy that we cannot (do) any rescue... we have 22 ambulances, four bus ambulances and a helicopter at the site," Pirhossein Koulivand, head of Iran's emergency services, told Iranian state television.

Ukraine's prime minister and Iranian state TV said 167 passengers and 9 crew were on board. Iranian TV said 32 of those on board were foreigners.

Television footage showed debris and smouldering engine parts strewn across a field, and rescue workers with face masks retrieving bodies of the victims.

According to air tracking service FlightRadar24, the plane that crashed was Flight PS 752 and was flying to Kiev. The plane was three years old and was a Boeing 737-800NG, it said.

The model's twin engines are made by CFM International, a U.S.-French venture co-owned by General Electric and France's Safran.

Modern aircraft are designed and certified to cope with an engine failure shortly after take-off and to fly for extended periods on one engine. However, an uncontained engine failure releasing shrapnel can cause damage to other aircraft systems.

A spokesman for Boeing said the company was aware of media reports of a plane crash in Iran and was gathering more information. The plane manufacturer grounded its 737 MAX fleet in March after two crashes that killed 346 people.

The 737-800 is one of the world's most-flown models with a good safety record and which does not have the software feature implicated in crashes of the 737 MAX.

Under international rules overseen by the United Nations, Iran is responsible for leading the crash investigation.

Ukraine would be involved and the United States would usually be accredited as the country where the Boeing jet was designed and built. France, where the engine maker CFM has half its activities, may also be involved.

There was no immediate word on whether the U.S. National Transportation Safety Board would be involved in the probe amid escalating tensions between the U.S. and Iran. The NTSB usually invites Boeing to give technical advice in such investigations.