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Airborne coronavirus: What you should know

NEW YORK (NYTIMES) – 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 Dr Linsey Marr, an aerosol expert at Virginia Tech.

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

What is clear, they said, is that people should consider minimising 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.

Here are answers to a few questions raised by the latest research.

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 organisations 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 aerosolised 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,” Dr 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,” Dr 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 Dr 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,” Dr 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 defence, 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 MINIMISE 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”, Dr 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, Dr 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 minimise 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.

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Covid-19 cases explode in California's San Quentin prison

LOS ANGELES (AFP) – The number of Covid-19 cases has exploded in one of California’s oldest prisons, San Quentin, as more than 1,000 inmates have tested positive for the virus, authorities in the US state announced on Tuesday (June 30).

“That is our deep area of focus and concern right now,” said governor Gavin Newsom, noting that 42 per cent of the some 3,500 inmates at San Quentin, near San Francisco, are considered “medically vulnerable”.

Unlike other penitentiaries in California, San Quentin State Prison had largely been spared the ravages of coronavirus until the beginning of June. But the transfer of inmates from prisons gravely affected by the virus, such as the California Institution for Men in Chino, opened the floodgates.

“Unfortunately, they arrived untested and were placed within San Quentin and really kind of seeded an outbreak in a second state facility,” Mr Matt Willis, the health director for Marin County, where San Quentin is located, told NPR radio.

The detention centre in Chino, near Los Angeles, was a known Covid-19 hotspot since the start of the pandemic. More than 500 inmates there have so far tested positive for the virus, and seven have died.

San Quentin prison currently makes up half of the recorded cases of Covid-19 in prisons throughout California, which has a total incarcerated population of about 113,000 people.

California is the most populated US state as well as one of the hardest-hit by the coronavirus, with more than 200,000 confirmed cases and nearly 6,000 deaths.

In an attempt to avoid an abnormally high mortality rate among inmates, state authorities have decided to free some 3,500 detainees, who were arrested for minor offences and had less than 180 days left to serve in prison.

Mr Newsom announced on Monday that another 3,500 potential candidates had been identified for freedom, 110 of whom are at San Quentin.

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Texas mayor orders curfew amid Covid-19 spread, Florida cases hit record high

HOUSTON (REUTERS) – A small city on the outskirts of Houston, Texas, has instituted a curfew starting on Saturday (June 27) night due to surging cases of the novel coronavirus, the latest move by officials in some southern and western states to backtrack on their reopening plans.

Underscoring the worsening spread of the virus, Florida on Saturday morning reported 9,585 new infections in the last 24 hours, marking a record high for a second day, and 24 additional deaths from Covid-19, the illness caused by the coronavirus.

The mayor of Galena Park, a community of 10,000 people east of Houston, said she was heeding a warning from Harris County Judge Lina Hidalgo, who on Friday raised the public threat level to its most severe, a sign people should shelter at home.

“It is crucial to continue to practise good hygiene, stay home as much as possible, avoid unnecessary trips, gatherings, and wear a face-covering at all times when you leave your home,” mayor Esmeralda Moya said in a statement late on Friday.

Galena Park’s curfew will run from 10pm to 5am daily.

The United States recorded more than 45,000 new cases of Covid-19 on Friday, the largest single-day increase of the pandemic, according to a Reuters tally, bringing the total number of Americans who have tested positive to at least 2.48 million.

The new record for positive Covid-19 tests came as Texas and other states at the centre of a new surge in infections took steps back from efforts to ease restrictions on businesses, threatening a hoped-for economic recovery and jobs.

In a reversal of his early moves to relax restrictions, Texas Governor Greg Abbott on Friday ordered bars across the state to close and required restaurants to limit indoor seating capacity to 50 per cent. Florida, another state that reopened its economy relatively quickly, told bar owners in the state to immediately stop serving alcohol on their premises.

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