Children infected with COVID-19 can shed the virus for weeks, even if they are asymptomatic or after their symptoms are clear, said a new study published Friday in the journal JAMA Pediatrics, reports Xinhua.

Researchers observed 91 children younger than 19 years old with COVID-19 from February 18 to March 31 in 20 hospitals and 2 non-hospital isolation facilities across the Republic of Korea.

About 22 percent of them were asymptomatic. Only 8.5 percent of symptomatic cases were diagnosed at the time of symptom onset, while 66.2 percent had unrecognized symptoms before diagnosis and 25.4 percent developed symptoms after diagnosis, according to the study.

SARS-CoV-2 RNA was detected for a mean of 17.6 days overall and 14.1 days in asymptomatic cases, said the study.

The results show symptom screening fails to identify most COVID-19 cases in children, and SARS-CoV-2 RNA in children is detected for an unexpectedly long time, according to the study.

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We’ve been told to stay at homes and not come out without urgent needs during the Covid-19 pandemic to keep ourselves safe. But we are not totally safe from the virus at home.

For months people were told to wash hands and maintain social distance to fight against coronavirus but scientists and engineers say there is a need to think about the air we are breathing, as countries around the world start gradually opening up educational institutions and offices.

Health experts say good ventilation could be the key to avoiding coronavirus as people spend more time indoors.

Good ventilation matters in five ways, reports BBC.

If it's stuffy, walk away

When you walk into a room and the air feels stale, then something is wrong with the ventilation. Not enough fresh air is being introduced, which increases chances of getting infected by coronavirus.

Recent research shows that in confined spaces there can be "airborne transmission" of the virus - with tiny virus particles lingering in the air.

According to workplace regulations set up before the pandemic, everyone should get 10 litres of fresh air every second, and that matters more than ever now.

So if a place seems stuffy, just turn around and leave, says Dr Hywel Davies, technical director of the Chartered Institution of Building Services Engineers.

"If you've got someone who's infected in a building, and you're bringing in plenty of outside air, you're diluting whatever infectious material they're giving off. You're reducing the risk of other people becoming infected," he said.

Read Also: Can the coronavirus spread through the air?

Look up at the air conditioning

The simplest air conditioner is a slender white box mounted on walls or ceilings, known as a split air conditioner.

This draws in air from a room, chills it and then blows it back out again. In other words, it's recirculating the air.

This is no problem for a quick visit but may be a risk over a period of hours.

A study of a restaurant in China blamed this type of air conditioner for spreading the virus.

Dr Davies points again to the importance of fresh air: "If there had been a good supply of outside air, very likely fewer people would have become infected - if any."

Ask about the 'fresh air ratio'

In a modern building where the windows are sealed, how can you get enough fresh air?

You're relying on a ventilation system in which stale air is extracted from the rooms and piped to an air handling unit, often on the roof.

There, fresh air can be pulled in from outside and mixed with the old inside air, before being sent back into the building.

Given the risk of coronavirus infection, the professional advice is to maximise the fresh supply.

"Having 100 percent outside air or close to 100 percent is a good thing," says Prof Cath Noakes of the University of Leeds and chair of the environmental panel of the government's SAGE advisers, speaking in a personal capacity.

"The more fresh air, the less you're running the risk of recirculating the virus through the building."

Check if there's virus in the filters

A modern ventilation system will have filters but these are not fool-proof.

In the US, researchers investigating the Oregon Health & Science University Hospital found that traces of coronavirus were trapped by the filters but some had somehow slipped through.

Prof Kevin van den Wymelenberg, who led the project, believes that swabbing the filters could reveal if there's someone infected working in a building.

In South Korea, a call centre on the 11th floor of an office building saw one person infect more than 90 others. If the filters had been checked more frequently, the presence of the virus might have been spotted sooner.

Watch out for draughts

Talk to any expert in the field and they will say that fresh air is the key.

But one specialist in modelling the movement of air says it's not that simple.

Nick Wirth used to design Formula 1 racing cars, and now advises supermarkets and food-processing companies on how to manage air flow to keep people safe.

He worries that if someone sitting beside an open window turns out to be infectious, they could shed virus to others downwind.

"If you open a window, where is the air going to go?" he asks. "We don't want people in a direct line of that airflow.

"More fresh air in general is better but if it's flowing horizontally and full of virus it could have unintended consequences."

Prof Cath Noakes says the benefits of plentiful fresh air diluting the virus will outweigh any risks.

An open window might lead to more people receiving the virus but in smaller, less risky amounts, in her view.

Coronavirus traces, reportedly found on packaging in China recently on consignments of frozen shrimp and frozen chicken wings from South America, has again raised questions about whether virus can be transmitted via food packaging, reports BBC.

What are the chances?

In theory, it may be possible to catch Covid-19 from packaging material.

Laboratory-based studies have shown that the virus can survive for hours, if not days, on some packaging materials - mostly cardboard and various forms of plastic.
 
What's more, the virus is more stable at lower temperatures, which is how many foods are transported.
 
However, some scientists have questioned whether these results could be replicated outside the lab.

 
Dr Julian Tang, associate professor of respiratory sciences at the University of Leicester, says that in the outside world, environmental conditions change rapidly, meaning that the virus can't survive as long.

And Emanuel Goldman, professor of microbiology at Rutgers University, has also pointed out that the lab studies used samples of up to 10 million viral particles, whereas the number of viral particles in - for example - an aerosol droplet sneezed on to a surface, was likely to be only about 100.

Writing in The Lancet in July, he said: "In my opinion, the chance of transmission through inanimate surfaces is very small, and only in instances where an infected person coughs or sneezes on the surface, and someone else touches that surface soon after the cough or sneeze (within one to two hours)."

Read Also: Global COVID-19 cases top 22.8 mn: JHU

How could the virus be transmitted?

The transmission risk is generally based on the assumption that workers in food packaging plants might touch contaminated surfaces, then touch their eyes, nose and mouth.

Scientists do not now think this is the main route of transmission for most Covid-19 cases.
 
"It may be possible that a person can get Covid-19 by touching a surface or object that has the virus on it," says the US health agency, the Centers for Disease Control (CDC) on its website.
 
However, it adds that "this is not thought to be the main way the virus spreads".

In fact, it is chiefly thought to spread directly from person to person:
 
•        Between people who are in close contact with one another (within 2m (6ft))
•        Through droplets produced when an infected person coughs, sneezes or talks
•        When droplets land in the mouths or noses of nearby people (or they are inhaled into the lungs)
 
Dr Tang says that proving someone had picked up the virus through packaging would also be difficult.
 
It would be necessary to ''exclude any recent exposure from any other source'' - including asymptomatic social contacts - to be certain that food packaging-related exposure was the true cause of an infection.
 
How can I stay safe?

The World Health Organization says "There is currently no confirmed case of Covid-19 transmitted through food or food packaging". But it does list a number of precautions you can take to avoid cross-contamination.
 
It says there is no need to disinfect food packaging, but "hands should be properly washed after handling food packages and before eating".
 
If you're shopping for groceries, use hand sanitiser before entering the shop if possible, and wash your hands thoroughly afterwards, and also after handling and storing your purchased products.
It should also be safe to have groceries delivered if the delivery worker follows good personal and food hygiene practices. You should also wash your hands after accepting food and grocery deliveries. Some experts also recommend only using plastic bags once.

Weight loss, whether from surgery or diet, has some metabolic benefits, according to a study from Washington University School of Medicine in St. Louis.

The researchers compared 11 gastric bypass surgery patients who had diabetes with 11 others who had diabetes and achieved equivalent weight loss with diet alone.

The average age of patients in the diet group was about 55, while the average in the surgery group was 49. Those in the surgery group lost an average of 51 pounds, while those in the diet group lost an average of 48 pounds, reports Xinhua.

Over a 24-hour period, the researchers used sophisticated techniques in a hospital setting to measure study subjects' metabolic responses to meals.

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They found the members of both groups experienced similar improvements in metabolism, such as lower blood sugar levels throughout the day, better insulin action in the liver, muscle and fat tissue, and reductions in the need for insulin and other diabetes medications.

"It has been suggested that weight loss induced by gastric bypass surgery is different from weight loss induced by a low-calorie diet, based on the fact that certain factors, such as increased bile acid concentrations, decreased branched-chain amino acid concentrations and alterations in the gut microbiome, are different in surgery patients and may be responsible for the unique therapeutic effects of gastric bypass surgery," said principal investigator Samuel Klein, director of Washington University's Center for Human Nutrition.

 "We found all of those factors were, in fact, different after weight loss in surgery patients than in patients who lost weight through diet alone. Yet those changes were not associated with any physiologically or clinically important metabolic benefits,” said the Samuel Klein.

The loss of weight is the reason for improvements in metabolic function and reversal of diabetes. Weight loss through dieting produces the same beneficial metabolic effects as weight loss following surgery, said Klein.

More than 40 percent of adult Americans are obese, and close to one in 10 is severely obese. Each year more than 250,000 people in the United States undergo bariatric surgery to help them lose weight.

The study was published Thursday in The New England Journal of Medicine.

Health misinformation on Facebook was viewed 3.8 billion times in the past year, peaking during the Covid-19 crisis, said a report of activist group Avaaz.

Avaaz which conducted the research, said Facebook posed a "major threat" to public health.

Doctors added false claims about vaccines on the social network could limit the numbers prepared to have a Covid jab if one became available.

Facebook said the findings did "not reflect the steps we've taken"

In a statement the firm said: "We share Avaaz's goal of limiting misinformation. Thanks to our global network of fact-checkers, from April to June, we applied warning labels to 98 million pieces of Covid-19 misinformation and removed seven million pieces of content that could lead to imminent harm.

"We've directed over two billion people to resources from health authorities and when someone tries to share a link about Covid-19, we show them a pop-up to connect them with credible health information."

Bogus cures

Despite its efforts, Avaaz's report suggests only 16% of the health misinformation it identified on Facebook carried a warning label.

The top 10 websites identified by researchers as spreading health misinformation had almost four times as many views on Facebook as information from official sites, such as the World Health Organization, according to the report.

A significant amount of health misinformation was shared from public pages.

And 42 of those pages were followed by more than 28 million people.

The type of content highlighted includes:

• 8.4 million views for an article claiming Bill Gates backed a polio vaccination that led to the paralysis of half a million children in India
• 4.5 million views for an article containing bogus cures for deadly diseases, such as colloidal silver for Ebola
• 2.4 million views for an article claiming quarantine harmed public health

The research looked at accounts from the US, UK, France, Germany and Italy.

Avaaz campaign director Fadi Quran said: "Facebook's algorithm is a major threat to public health.

"Mark Zuckerberg promised to provide reliable information during the pandemic.

"But his algorithm is sabotaging those efforts by driving many of Facebook's 2.7 billion users to health-misinformation-spreading networks.

"This info-demic will make the pandemic worse unless Facebook detoxifies its algorithm and provides corrections to everyone exposed to these viral lies."

'Toxic lies'

Avaaz called on the social network to provide everyone who had viewed health misinformation on its platform with independently fact-checked corrections.

It also said it should downgrade misinformation posts in news feeds, in an attempt to lessen their reach.

Prof Frank Ulrich Montgomery, who chairs the World Medical Association, said: "This pandemic should be a powerful reminder of how successful vaccines have been.

"But instead anti-vaxxers are using Facebook to spread toxic lies and conspiracy theories."

European Union of Medical Specialists secretary general Dr Joao Miguel Grenho said: "Mark Zuckerberg must take immediate action to stand with us to stop this info-demic.

"Otherwise the number of people poisoned against taking a vaccine will be too high for us to beat this pandemic."

Facebook insists it is combating dangerous health myths.

And if you put the word "vaccines" in its search box, you do get pointed towards reliable information.

But it is also easy to find thousands of groups and individuals spreading misinformation with no apparent intervention from Facebook.

A case in point is a page called Kate Shemirani - who calls herself Natural Nurse in A Toxic World and stresses her qualifications.

In fact, Ms Shemirani's nursing registration was suspended by the Nursing and Midwifery Council in July, after complaints she was spreading false information about Covid-19 and about vaccines.

'Killed thousands'

A glance at what she posts on Facebook and Twitter reveals relentless attacks on Bill Gates, the wearing of masks and NHS staff, whom she calls criminals and liars for perpetuating the "hoax" that is the coronavirus.

But much of her content is about vaccines - this week she claimed the polio vaccine caused polio and had harmed and killed thousands.

We forwarded this post to both Facebook and Twitter to ask if it broke their rules.

While Twitter would not give a public statement, it indicated its rules covered Covid-19 only, so did not affect this post.

Facebook said that while it doesn't prevent people from saying things that are factually incorrect, it has acted to make this and similar posts less prominent in people's news feeds.