Что такое вирус people

More evidence is emerging that coronavirus infections are being spread by people who have no clear symptoms. The findings complicate efforts to gain control of the pandemic

NEW YORK -- Scientists offered more evidence Wednesday that the coronavirus is spread by seemingly healthy people who show no clear symptoms, and the federal government issued new guidance warning that anyone exposed to the disease can be considered a carrier.

A study by researchers in Singapore became the latest to estimate that somewhere around 10% of new infections may be sparked by people who carry the virus but have not yet suffered its flu-like symptoms.

In response to that study and others, the Centers for Disease Control and Prevention changed how it defined the risk of infection for Americans. The agency's new guidance targeted people who have no symptoms but were exposed to others with known or suspected infections. It essentially says that anyone may be a carrier, whether that person has symptoms or not.

The findings complicate efforts to gain control of the pandemic and reinforce the importance of social distancing and other measures designed to stop the spread, experts said.

“You have to really be proactive about reducing contacts between people who seem perfectly healthy,” said Lauren Ancel Meyers, a University of Texas at Austin researcher who has studied coronavirus transmission in different countries.

The newest research was published online by the CDC. It focused on 243 cases of coronavirus reported in Singapore from mid-January through mid-March, including 157 infections among people who had not traveled recently. Scientists found that so-called pre-symptomatic people triggered infections in seven different clusters of disease, accounting for about 6% of the locally acquired cases.

One of those infections was particularly striking. A 52-year-old woman's infection was linked to her sitting in a seat at a church that had been occupied earlier in the day by two tourists who showed no symptoms but later fell ill, investigators said after they reviewed closed-circuit camera recordings of church services.

An earlier study that focused on China, where the virus was first identified, suggested that more than 10% of transmissions were from people who were infected but did not yet feel sick.

The seemingly healthy people who can transmit the virus are believed to fall into three categories: pre-symptomatic, who do not have symptoms when they spread but develop illness a couple of days later; asymptomatic, who never develop symptoms; and post-symptomatic, who get sick and recover but remain contagious. The Singapore and China studies focused on pre-symptomatic infections.

It remains unclear how many new infections are caused by each type of potential spreader, said Meyers, who was not involved in the Singapore study but was part of the earlier one focused on China.

CDC officials say they have been researching asymptomatic and pre-symptomatic infections, but the studies are not complete.

In an interview Tuesday with a radio station in Atlanta, CDC Director Dr. Robert Redfield cited an estimate that 25% of infected people may be asymptomatic. It was not clear what that estimate was based on, or if it included people who were pre-symptomatic or post-symptomatic. The AP requested more information from the CDC, but the agency did not provide those details.

Redfield's comment was in response to a question about whether the agency is going to recommend that people who seem healthy wear masks or face coverings when they go out. He said the agency is reviewing its guidance, looking at research in Singapore, China and other places in making that decision.

California Gov. Gavin Newsom this week said he planned to announce new state guidelines on wearing masks.

Wearing scarves or bandanas over noses and mouths is “not necessarily going to protect you, but if you are carrying the disease, it may reduce the amount you transmit,” said Carl Bergstrom, a University of Washington evolutionary biologist who studies emerging infectious diseases.

In the initial months of the pandemic, health officials based their response on the belief that most of the spread came from people who were sneezing or coughing droplets that contained the virus.

Another kind of coronavirus caused the deadly severe acute respiratory syndrome, or SARS, which was first identified in Asia in 2003 and caused a frightening but relatively short-lived international outbreak that never spread as widely as the new virus.

Although some asymptomatic infections were discovered, none were found to have spread the disease. Because symptomatic people were the spreaders, health officials could focus on them to see an outbreak happening and could better isolate infected people and stop the spread.

“It was much, much easier” to contain, Bergstrom said. With the new coronavirus, “we clearly have asymptomatic and pre-symptomatic transmission,” he added.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

Share this with

These are external links and will open in a new window

These are external links and will open in a new window

Close share panel

Stories of people emptying supermarket shelves or arguing over packets of pasta can paint a bleak picture of the coronavirus outbreak. But there are also acts of kindness that have inspired thousands of others.

Beauty Banks, a charity that supplies essential toiletries to people in poverty, launched an emergency virus-related appeal on Sunday.

"Since just after noon yesterday we've raised £60,000 to pay for soap, hand sanitiser, washing powder and so on to help people who don't have the money to stockpile," said columnist Sali Hughes, who co-founded the campaign two years ago.

"Because we're an existing charity we work with suppliers already. We think we can get our hands on, certainly for the first drop, a lot of hand sanitiser for people who really, really need it."

Ms Hughes said because of the coronavirus outbreak people are more able to relate to the idea of not being able to get items they need.

"This is the first time lots of us have looked at shelves and thought actually I need something and I can't have it, and so they're better able to relate to people living in poverty who feel like that quite a lot of the time.

"I think it's really important in times of crisis, when people are doing something positive it does make you feel a little bit calmer and more in control. It certainly does me.

"I do think the act of giving just makes us feel better. It feels as though we're doing something, we're part of a collective effort."

In Altrincham, Greater Manchester, Rachel Pleasant is recruiting volunteers to help local residents who are elderly, vulnerable or stuck at home without any family or friends nearby. She and two others set up a Facebook group on Saturday.

"Before we know it we've had 2,000 people join the page and 3,500 messages of support saying please let us help. It's been amazing."

They have got hold of ward maps of the local area and have been divvying up streets to volunteers, who will visit residents and offer to run errands or pick up supplies.

"I think we just felt panic never solves anything, let's focus some of that energy on really helping the people in our community."

Facebook said more than 200,000 people in the UK are now members of more than 300 local support groups set up for the virus.

Brie Rogers Lowery, from the social media site, said it was "heartening" to see people rallying round.

'Darrell's memory'

The family of 88-year-old Darrell Blackley, who died at North Manchester General Hospital on Friday after testing positive for coronavirus, have asked people to carry out acts of kindness in his memory.

"We invite you to forget flowers and cards," said the message, written on behalf of his family.

"Instead we would like you to give acts of kindness. Help someone who is lonely or struggling during this time, who needs shopping, childcare or a chat.

"Post tiny acts of kindness given and received and share. Build something beautiful in Darrell's memory."

• EASY STEPS: What should I do?
• A SIMPLE GUIDE: What are the symptoms?
• HEALTH MYTHS: The fake advice you should ignore
• LOOK-UP TOOL: Check cases in your area
• MAPS AND CHARTS: Visual guide to the outbreak

Ali Currie, from south London, said her two daughters, Scarlet, 10, and Grace, 12, posted handwritten notes to the houses on their road.

"They are pretty caring girls," she said. "We live in a really lovely neighbourhood which is full of great community spirit."

The family have received a few texts and handwritten notes in return and their elderly next door neighbour "said she will need some help at some point".

"It's been great to see kindness spread so fast and so far," said Becky Wass, whose separate postcard campaign aimed at helping people look out for their neighbours was shared widely on social media.

The postcard, which people can print at home, allows neighbours to offer to deliver shopping, drop off urgent supplies or talk on the phone, and gives the recipients their name and phone number to contact.

"The response has been incredible," said Ms Wass, from Falmouth in Cornwall. "I'm now hearing heartwarming stories from around the world about people connecting with their neighbours."

But it is not just thoughtful individuals who are helping others during the health crisis. Businesses - many of which are likely to suffer a hard time if social distancing measures increase - are also getting involved.

One hotel in Portaferry, County Down, said it is offering to deliver free dinners to elderly people who are unable to get to a supermarket or restaurant.

"These are unprecedented times and we are a close knit community; let's stick together and get through this together," the hotel said on Facebook.

Meanwhile, a grocers in Padstow is setting aside half an hour every day solely for shoppers who were born in 1950 or before.

The owner said he hoped it would give elderly shoppers "a little bit of peace of mind" in the fight against coronavirus.

Other cafes and shops are doing similar. A cafe in Glasgow's Southside is delivering soup to the elderly and people with underlying health issues, while a shop in Stenhousemuir is dropping off packages of hand gel to local pensioners.

The head of the World Health Organization, Tedros Adhanom Ghebreyesus, has regularly expressed his gratitude to those trying to spread kindness.

He shared a video of a fitness instructor in Seville, in Spain, who held an exercise class for quarantined residents in an apartment block who joined in on their balconies.

"I am so impressed and inspired by all the examples of kindness and compassion people are showing around the world," said Dr Ghebreyesus.

"With this spirit, we can beat coronavirus."

Share this with

These are external links and will open in a new window

These are external links and will open in a new window

Close share panel

Many older people are being "airbrushed" out of coronavirus figures in the UK, charities have warned.

The official death toll has been criticised for only covering people who die in hospital - but not those in care homes or in their own houses.

Work and Pensions Secretary Therese Coffey told the BBC the daily figure was based on hospital deaths because "it's accurate and quick".

Meanwhile, scientists will begin a review of the UK lockdown later.

The latest figures from the Office for National Statistics, which include every community death linked to Covid-19 in England and Wales, showed a total of 406 such deaths registered up to 3 April had occurred outside of hospitals.

That would have added an extra 11% to the official UK figures, based solely on deaths in hospitals, that were being reported at that time.

Of those extra deaths, 217 took place in care homes, 33 in hospices, 136 in private homes, three in other communal establishments and 17 elsewhere.

Northern Ireland's chief medical officer has said details about the number of coronavirus-related deaths in care homes remain unclear, but it was reported last week that there were cases of Covid-19 in 20 care homes across the nation.

• A SIMPLE GUIDE: How do I protect myself?
• AVOIDING CONTACT: The rules on self-isolation and exercise
• WHAT WE DON'T KNOW How to understand the death toll
• TESTING: Can I get tested for coronavirus?
• LOOK-UP TOOL: Check cases in your area

Industry leaders from Age UK, Marie Curie, Care England, Independent Age and the Alzheimer's Society have written to Health Secretary Matt Hancock demanding a care package to support social care through the pandemic.

They have also called for a daily update on deaths in the care system.

It comes after the government confirmed there had been coronavirus outbreaks at more than 2,000 care homes in England - although they did not specify the number of deaths that had occurred.

The figures prompted the charity Age UK to claim coronavirus is "running wild" in care homes for elderly people.

"The current figures are airbrushing older people out like they don't matter," Caroline Abrahams, the charity's director, said.

Meanwhile, Britain's largest care home operator, HC-One, said coronavirus was present in two-thirds - 232 - of the group's care homes.

Its director, Sir David Behan, told BBC Radio 4's Today programme that coronavirus deaths represented about one-third of all deaths at HC-One's care homes over the last three weeks. HC-One has 329 care homes throughout England, Scotland and Wales.

MHA, a charity which operates 131 homes, said there had been 210 coronavirus-related deaths.

About 410,000 people live in care homes in the UK, living in 11,300 care homes for older people supplied by 5,500 different providers.

Addressing why deaths in care homes are not being included in the government's data, Ms Coffey told BBC Radio 4's Today programme that the figures published weekly by the ONS is a "fair" way of establishing the "unfortunate picture" of where deaths are occurring.

England's care home regulator, the Care Quality Commission, has said it will begin recording deaths in adult social care from this week - asking care providers to give daily updates on the number of confirmed and suspected cases.

Labour's shadow social care minister Liz Kendall said daily figures were essential to dealing with the "emerging crisis" in care homes and called for the government to offer social care "whatever resources it needs".

Conservative peer and former work and pensions minister Baroness Altmann told Today that "one or two" people in care homes had said to her they felt as though older people are being treated "like lambs to the slaughter".

"They [care homes] are left without protective equipment, they are left without testing," she said.

She added that "the mark of a civilised society" was "how it treats it most vulnerable and oldest citizens".

It comes after Ms Abrahams said care homes were "underprepared" for the outbreak, adding that the lack of personal protective equipment (PPE) and testing was leading to the spread of coronavirus across the care home sector.

However, Ms Coffey told the Today programme that the care sector was not being left behind, adding that PPE was being delivered "to over 26,000 care settings across the country including care homes, home care providers and also hospices".

On Monday, the UK's chief medical adviser Prof Chris Whitty told the daily Downing Street coronavirus briefing that 92 homes in the UK reported outbreaks in one day.

The Department of Health and Social Care later confirmed 2,099 care homes in England have so far had cases of the virus.

Care England has estimated there have been nearly 1,000 deaths from coronavirus in care homes, leaving social care as "the neglected front line".

The Labour Party has called on the government to publish daily figures of deaths in care homes to highlight the "true scale" of the spread of the virus, which causes the Covid-19 disease.

The issue has regularly been raised by journalists at the daily Downing Street briefing and the government response has been that the number announced each day is based on hospital figures as this can be quickly gathered and analysed - whereas deaths in the wider community take much longer to be collated after death certificates are issued by doctors.

The government says it is following the international standard by quoting the hospital figures each day - and that the fuller ONS figures can lag many days behind.

The latest care homes to confirm residents have died with symptoms of the virus include a home in Drumchapel, Glasgow, a specialist dementia home in Selston, Nottinghamshire, and a home in County Durham where 13 residents have died.

The Department of Health's official death number of deaths of people in hospital with coronavirus rose to 11,329 on Monday - up by 717 in a day.

Lockdown review

The BBC's science editor David Shukman said the Scientific Advisory Group for Emergencies (Sage) meeting later in the day will evaluate various ways coronavirus is unfolding in the UK.

It will look at hospital admissions, the approach to testing, data on intensive care capacity and deaths, the effectiveness of lockdown tactics, and whether or not the public should be advised to wear face masks outdoors.

Meanwhile, the government has defended itself after reports it missed three chances to bulk-buy PPE for healthcare workers treating virus patients.

Health workers in 25 EU countries are set to receive deliveries of kit worth £1.3bn in the coming days, according to the Guardian.

The paper reports the UK missed three opportunities to join the scheme and has not taken part in talks on future purchases.

The Department of Health said it would "consider participating in future EU joint procurement schemes on the basis of public health requirements at the time".

"We will continue to work with European countries and others in order to make sure that we can increase the capacity within the NHS," they said.

In other developments:

• Gym and leisure centre bosses say urgent action is needed to safeguard exercise venues, as unscrupulous landlords use a loophole to threaten eviction over non-payment of rent during the coronavirus crisis
• Co-op chief executive Steve Murrells has said he is donating a fifth of his wages over the next three months to launch a fund for food banks and other community causes during the pandemic
• Retail giant Next will begin selling online again on Tuesday after pausing operations for two weeks while measures were introduced to keep warehouse staff safe; measures include that workers will wear tabards displaying the message "stay 2m apart"
• The Scottish government has rejected claims that manufacturers of protective equipment are prioritising workers in England, with clinical director Prof Jason Leitch dismissing them as "rubbish"
• More than 1,000 rough sleepers in London are now self-isolating in hotel rooms and other safe locations, London Mayor Sadiq Khan said. He said one hotel in east London has been turned into a specialist care facility for homeless people who have developed coronavirus symptoms

How have you adapted to isolation during the pandemic? Do you have an relative living in a care home? Are you a care home employee? Share your experiences by emailing haveyoursay@bbc.co.uk .

Please include a contact number if you are willing to speak to a BBC journalist. You can also contact us in the following ways:

“It’s not about you, it’s about everybody else.”

Share this story

This story is part of a group of stories called

Finding the best ways to do good.

If you think you don’t have a huge role to play in how the coronavirus outbreak plays out, think again. You have the potential to make this pandemic so much worse.

That’s because the coronavirus is both more contagious and more deadly than the common flu. One person can easily transmit it to other people without knowing it, and those people would then transmit it to even more people, creating a terrifying snowball effect.

The good news is, just as you can easily transmit the virus to other people, you can easily avoid transmitting it — if you’re willing to stay home. That’s right: Simply by sitting on your couch, you can potentially save lives.

To see why, check out the visualization below. It shows how one person with the coronavirus, who passes on the virus to three other people (some experts say three is the average, though others estimate the infectiousness is a bit lower), can very quickly spawn a public health nightmare that afflicts thousands of people. But it also shows how one person can mitigate that effect through social distancing. By avoiding the office, the barbecue, the airport, and so on, an individual can deprive the virus of the opportunity to infect more people.

One striking real-world example of this phenomenon is the woman known as Patient 31. South Korea had only 30 cases of Covid-19 until, in February, she became infected and started inadvertently spreading the virus. Despite having a fever, she had lunch with a friend at a hotel and attended church services, coming into physical contact with many of the worshippers. In a matter of days, hundreds of people from the church and its environs tested positive for Covid-19.

You do not want to be Patient 31.

This is why even if you’re young and healthy and falsely believe the virus can’t kill you (it can), you’d do well to stay home in order to protect others — especially older and immunocompromised people who are at greater risk of dying if they contract Covid-19, as well as the health care workers who have to expose themselves to the risk every day.

Believe it or not, through the simple act of staying home, you can save many people — even many thousands of people — from contracting the virus.

Hugh Montgomery, director of the Institute for Human Health and Performance at University College London, broke down the math in an incredibly clear and simple video.

This is the best and clearest explanation of why people need to stay at home you could ever wish to see pic.twitter.com/49MgadlctI

To figure out just how infectious a disease is, experts use the basic reproduction number, called the R0 (pronounced “R naught”). That refers to how many other people one sick person will infect on average in a group that doesn’t already have immunity. The higher the R0, the higher the likelihood that many people will get sick.

The R0 for the common flu is 1.3. So, if you get the flu, you will, on average, pass that on to 1.3 people. Montgomery calculates that if each of those 1.3 people pass it on to another 1.3 people, and that keeps on happening 10 times, then by the 10th time, 14 people will have the flu.

(That’s because 1.3 to the power of 10 is 13.786. He’s rounding up a bit.)

The coronavirus, however, is more contagious than the common flu. Experts are still trying to figure out the R0, and in any case it’s not something that’s precisely fixed, since diseases behave differently in different environments and some people (known as “super-spreaders”) are more contagious than others. But the World Health Organization says most estimates of the coronavirus’s R0 are around 2 or 2.5, while some estimates put it as high as 3.11. Montgomery uses an R0 of 3 to make his calculations.

“So every person passes to it three — now that doesn’t sound like much of a difference, but if each of those three pass it to three and that happens in 10 layers, I have been responsible for infecting 59,000 people,” he says.

(That’s because 3 to the power of ten is 59,049. He’s rounding down a bit.)

Montgomery’s back-of-the-envelope math simplifies reality a little; for example, he assumes that all the people in all 10 layers of transmission will be susceptible to contracting the virus, whereas some might already have immunity to it. But his basic point holds up.

And the conclusion he draws at the end is crucial: “If you are irresponsible enough to think that you don’t mind if you get the flu, remember it’s not about you — it’s about everybody else.”

Although it can be genuinely hard to act altruistically when the beneficiaries are so invisible — after all, you won’t be able to see the grandfather or nurse you’ve kept from getting sick — please know that the benefits are real nonetheless.

Every day that you practice social distancing during the pandemic, you’re doing someone else (maybe hundreds or even thousands of someone elses) a great kindness. So if you can, stay home. It’s the easiest act of heroism you’ll ever do.

Sign up for the Future Perfect newsletter and we’ll send you a roundup of ideas and solutions for tackling the world’s biggest challenges — and how to get better at doing good.

Get our newsletter in your inbox twice a week.

Future Perfect is funded in part by individual contributions, grants, and sponsorships. Learn more here.

For every person who tests positive, there's likely another handful of asymptomatic people who don't know they're infected.

For every person who tested positive for the coronavirus in China, there were likely another five to eight asymptomatic people who didn't know they had the infection, according to a new study. What's more, these undocumented cases likely infected the majority of known — and thus likely more severe — cases.

As the world continues to battle the coronavirus known as SARS-CoV-2, the case counts continue to tick upward, rapidly filling online virus-spread maps with an unsettling coat of red. But underlying this very visible threat is an entirely different map outlining the movement of the coronavirus's invisible vehicles: people who have very mild or no coronavirus symptoms at all.

To figure out just how many COVID-19 cases went undocumented, a group of researchers from five institutions across the world crunched the early numbers from China, where the outbreak first began.

The researchers created a mathematical model that analyzed the number of infections in 375 Chinese cities. Their model included travel time and distance traveled for people who participated in the country's Chunyan, or Spring Festival Period — which began Jan. 10 — by analyzing data from 2018. They then simulated observations between Jan. 10 and Jan. 23 from this year before China implemented travel restrictions.

Based on the model, during this time period, China should have had 86% more cases of COVID-19 than what the country had reported. And those undocumented cases were about half as likely as the documented cases to infect another person.

Part of the reason is that people with mild cases or asymptomatic cases likely have lower amounts of virus in their systems that they could shed, co-author Sen Pei, an associate research scientist at Columbia University's Mailman School of Public Health. However another study, though small in size, found that the coronavirus might be most infectious when symptoms are mildest, according to a Live Science report. The other reason is that these people sneeze and cough less than people with more severe diseases, Pei added.

Yet, their modeling showed that because there were so many undocumented cases, these people were the source of infection for 79% of all documented cases before Jan. 23. The virus has the potential to spread through the air and so could be spread just by speaking to an infected person; it can also spread by touching a surface that was contaminated by an infected individual, Pei told Live Science.

That means that even health care professionals who are caring for these patients carry the risk of spreading the coronavirus, especially without having access to proper gear. "Asymptomatic cases, no matter whether they are health care workers or not, can be contagious," Pei said.

These numbers will differ from country to country, as each will have different testing capacities. "Our estimate is specifically for China, so it's not necessarily transferable to the U.S," Pei said. Still, if mild or asymptomatic infections were counted, the mortality rate would be lower, he added.

"There's certainly transmission by less symptomatic people in the U.S., too," said Dr. Robert Horsburgh, a professor of epidemiology and medicine at Boston University School of Public Health and School of Medicine, who wasn't part of the study. "As we get more tests and better tests, I think we'll be able to identify more of those people."

However, the authors "overstated their case somewhat," Horsburgh said. There have been a number of studies that came out analyzing the data from China that have found lower percentages of asymptomatic people, and the reason is likely because this new study lumped together people who didn't get tested as being in the asymptomatic category, he added. But "in the early epidemic in China, just like in the U.S., they didn't have enough tests."

Recently, Dr. Robert Redfield, director of the Centers for Disease Control and Prevention (CDC), told NPR that 1 in 4 people with COVID-19 could be asymptomatic in the U.S. So while the exact numbers in the U.S. aren't yet clear, social distancing "is working, and we need to stick with it," Horsburgh said. Once testing becomes more widespread, "we can switch to the other strategy of isolating the infected people," rather than everybody, he said.

The findings were published March 16 in the journal Science.

With impressive cutaway illustrations that show how things function, and mindblowing photography of the world’s most inspiring spectacles, How It Works represents the pinnacle of engaging, factual fun for a mainstream audience keen to keep up with the latest tech and the most impressive phenomena on the planet and beyond. Written and presented in a style that makes even the most complex subjects interesting and easy to understand, How It Works is enjoyed by readers of all ages.
View Deal