WHO withdraws claim that people with asymptomatic COVID-19 are not contagious
On June 10, experts from the World Health Organization tried to clarify the statement made that asymptomatic transmission of coronavirus occurs in "very rare" cases, writes MarketWatch.
WHO's Technical Director for COVID-19 Response Maria Van Kerchow said it was “a misunderstanding claim that asymptomatic transmission in the world is very rare”And that her comments during the WHO news briefing were based on“ a very small subset of the studies ”.
“I was just answering the question; I didn’t state the WHO policy, ”she said.
WHO estimates that currently 16% of people with COVID-19 are asymptomatic and can transmit coronavirus, while other data show that 40% of coronavirus transmission is due to cases of asymptomatic carriage.
Health officials recommended that people stay 6 feet (about 2 meters) apart. Face masks are designed to prevent the transfer of invisible drops to another person and, thus, not to infect him. This is also protection from a person who may be infected with COVID-19, but who has very mild or no symptoms.
But "there's nothing magical about six feet," said Gregory Poland, who is studying the immunogenetics of vaccine response in adults and children at the Mayo Clinic in Rochester, Minnesota, and is an expert on the American Society for Infectious Diseases.
“The virus does not measure distance,” he said. - For example, a viral cloud during a call extends 27 feet (8,2 meters) and lingers in the air for about 30 minutes. It's more like the flu in the sense that people transmit the virus before they show any symptoms, and some of course won't get sick. "
The asymptomatic transmission “is the Achilles heel of the fight against the COVID-19 pandemic using the public health strategies that we are currently implementing,” according to a study by experts from the University of California, San Francisco, published May 28 in the New England Journal of Medicine.
“Symptom-based screening is helpful, but epidemiological evaluations of COVID-19 outbreaks in skilled nursing facilities strongly demonstrate that our current approaches are inadequate,” write researchers Monica Gandhi, Deborah Yokoe and Diane Hawleer.
Symptom detection and subsequent testing to determine isolation and quarantine procedures were justified by the similarities between SARS-CoV-1 (the virus that caused SARS SARS) and SARS-CoV-2 (the virus that caused the coronavirus infection COVID-19), the researchers wrote.
Gandhi, Yokoye and Hawlir stated that these symptoms include a high genetic link between viruses, transmission mainly through the respiratory drops and regularity of symptoms in the lower respiratory tract (fever, cough and shortness of breath), with both infections developing on average 5 days after infection.
“Despite the deployment of similar controls, the trajectories of the two epidemics have turned in completely different directions,” they added. "SARS was brought under control within 8 months after SARS-CoV-1 infected approximately 8100 people in limited geographic areas."
The number of confirmed cases of COVID-19 continues to rise. Less than 6 months after the first reports of the new coronavirus, the COVID-19 pandemic, first identified in Wuhan, China in December, has infected 7 people worldwide and 960 in the United States as of Monday, June 856. According to the Center for Systems Science and Engineering at Johns Hopkins University, at least 2100 people died in the world, 749 of whom were in the United States.
Here are five reasons to worry about asymptomatic virus transmission:
1. COVID-19 creates a high viral load in the upper respiratory tract
A study by the University of California at San Francisco showed that there is a high viral load of SARS-CoV-2 in the upper respiratory tract, even among presymptomatic patients, "which distinguishes it from SARS-CoV-1, where replication occurs mainly in the lower respiratory tract" .
"Symptom-related SARS-CoV-1 viral loads peak on average 5 days after SARS-CoV-2 viral loads, making symptom-based infection detection more effective for SARS CoV -1." written by researchers.
Regarding influenza, they added, "people with asymptomatic disease usually have a lower quantitative viral load in secret from the upper respiratory tract than from the lower respiratory tract and a shorter duration of virus isolation than people with symptoms."
2. Outdoor joggers can create a “viral plume” up to 30 feet (9 meters)
In April, after several weeks of confusion about the effectiveness of face masks, the Trump administration and the Centers for Disease Control and Prevention announced that Americans should wear them. Some studies show that transmission of the virus is more likely without a mask.
“A running person who doesn't yet know he is sick and is running in front of you will likely infect you with a stream of air that travels up to 30 feet behind him,” Poland said. "At 6 feet, the largest breathing droplets land on the ground."
“The WHO told us that you don't need to wear a mask, and then you need to,” he added. “If only a few people are sick in the hospital room, you can still cultivate the virus from door handles and light bulbs. It may also happen that the risk of transmission is higher when people cough and sneeze. ”
3. Some experts say the effectiveness of the masks is mixed
“If you are not wearing PAPR, a self-contained breathing apparatus, there is no clear safety issue,” says Poland. - These are the so-called space suits. The only thing that can be said is that it is safer than without them. You can't be 100% safe with social distancing and masks. "
“All these things together form a network of your protection. You do not get in a car without seat belts, brakes, tires, airbags. Even one of these things matters. The same applies to the so-called non-drug interventions. ”
Poland added: “I am worried that people who have antibodies or who receive the vaccine will have a kind of 'freedom of freedom'. This virus has very specific immunological secrets embedded in it. We are still studying influenza and have been working on it since the 1940s. ”
4. A contact tracking system is critical
“Asymptomatic transmission raises the need for increased testing capacity and close contact tracing to detect asymptomatic infections, interrupt undetected transmission chains and further bend the curve downward,” the CDC guidelines said.
If it is determined that the cause of the new coronavirus pandemic is asymptomatic or slightly asymptomatic carriers of SARS-CoV-2 infection, “innovations in the detection and prevention of diseases may be required in addition to exhaustive contact tracing, mass testing and isolation of asymptomatic contacts.”
The CDC said that it is necessary to know more, in particular, whether these people develop full or partial immunity, how long protective immunity lasts, and whether it is possible to be protected from reinfection and at the same time transfer COVID-19 to another person, remaining asymptomatic.
5. Asymptomatic and pre-symptomatic course is a bad combination
According to a study by William Petrie, a professor of medicine and microbiology at the University of Virginia who specializes in infectious diseases, 10 to 43% of people infected with COVID-19 (depending on the sample group) did not have symptoms of the disease.
“Asymptomatic SARS-CoV-2 infection appears to be common and will continue to complicate efforts to control the pandemic,” writes Petri. - Asymptomatic carriers also range from 5% to 25% for influenza.
As many US states reopen, Carlos de Rio, a professor of global health and epidemiology at the Rollins School of Public Health at Emory University, said it’s best to avoid long contact with others.
“Working in an office with someone is what worries me,” he said.
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