How contagious is someone who has contracted COVID-19 – showing no symptoms yet – and what makes them asymptomatic while other people suffer so terribly from the disease?
This study, published this week in the medical journal JAMA Internal Medicine, provides one theory for the first question. It isolated 303 patients with COVID-19 in a treatment center in South Korea. Of these, 110 (36%) were asymptomatic and 21 (19%) developed symptoms during isolation.
The potential for transmission of asymptomatic humans has been cited as an important factor in controlling the spread of COVID-19, but there is limited information on the clinical course and viral load of asymptomatic humans with SARS-CoV-2. infection, “the researchers wrote.
What they found: “Many individuals with SARS-CoV-2 infection remained asymptomatic for a long time, and viral load was similar to that in symptomatic patients,” the scientists concluded. “Therefore, isolation of infected persons should be performed, regardless of symptoms.”
The study was led by Seungjae Lee, an associate professor at Soonchunhyang University College of Medicine in South Korea, was peer reviewed, and previously conducted in the pandemic; the researchers analyzed swabs taken from the group between 6 and 26 March.
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‘Many individuals with SARS-CoV-2 infection remained asymptomatic for an extended period of time, and viral load was similar to that in symptomatic patients.’
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Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, said that in his 40 years of dealing with viral outbreaks he has never seen anything like COVID-19, especially in one single way that helped lead to one of the largest public health crisis in a generation.
“I’ve been dealing with viral outbreaks for the last 40 years. “I have never seen a single virus – that is, one pathogen – reach a range where 20% to 40% of people have no symptoms,” he told a recent House Energy and Commerce Committee on the new coronavirus pandemic.
The World Health Organization currently estimates that 16% of people with COVID-19 are asymptomatic and can transmit the coronavirus, while other data show that 40% of coronavirus transmission is due to carriers who have no symptoms of COVID-19. display disease.
The infectiousness of asymptomatic individuals relative to those who are symptomatic is 75%, according to the Centers for Disease Control and Prevention, based on studies of dynamic “viral shedding” – that is, how much of the virus they transmit through conversation or breathing.
Not everyone responds the same to COVID-10 infection. “The different host immune responses to SARS-CoV-2 infection may explain in part why men and women, young and old who are infected with this virus have markedly different degrees of disease,” these Chinese researchers wrote.
So why are some people asymptomatic while others are not? “SARS-CoV-2, which is the virus causing coronavirus disease 2019 (COVID-19), uses the angiotensin-converting enzyme 2 (ACE2) as a cell receptor to invade human cells,” she added.
Those ACE2 receptors as ‘doorways’ seem to be more likely in older people and those who are obese than younger people. That may be something to explain why so many young people are not as badly affected by the virus as, say, older than 60.
Earlier exposure to other coronaviruses, which can give humans “T-cell immunity” to similar viruses, and a lower viral load of COVID-19 and other fortunate genetic variations, may also contribute to why some people are less pregnant or have no symptoms of infection.
There is currently no vaccine for COVID-19, although several companies say they have made progress with trials. Unlike influenza viruses where there are several vaccines, humans generally have not built up immunity to COVID-19 over multiple generations.
Related: Feeling good about masks? Think again. Here’s how many lives can be saved if everyone wore a mask – starting today
The public has been confused about the number of asymptomatic people and how contagious they are.
MarketWatch Photo Illustration / iStockphoto
But a strong immune response to an infection from a virus like COVID-19 can sometimes cut both ways. Fall in point: Doctors and members of the public were ridiculed for how otherwise strong, healthy people fell victim to the 1918 flu.
Doctors today attribute this to the ‘cytokine storm’, a process in which the immune system in healthy people reacts as strongly as the body hurts and eventually causes damage to the organs and, in the worst cases, organ failure.
A characteristic of some viruses: An emergence of immune cells and their activating compounds (cytokines) effectively turned the body against itself, leading to an inflammation of the lungs, severe respiratory distress, making the body vulnerable to secondary bacterial pneumonia.
“A major difference between Spanish flu and COVID-19 is the age distribution of deaths,” according to a recent report by Deutsche Bank DB,
“For COVID-19, the elderly are overwhelmingly the worst hit, but the young working-class population was hit hard in 1918.
“In fact, the death toll from pneumonia and flu that year among 25-34-year-olds in the United States was more than 50% higher than that for 65-74-year-olds. A remarkable difference for Covid-19, ”said Deutsche Bank.
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Asymptomatic transmission ‘is the Achilles’ height of Covid-19 pandemic control. ‘
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Public health officials have advised people to keep a distance of six feet from each other. Face masks are designed to prevent the carrier, which can be infected with COVID-19 but is very mild and has no symptoms, from spreading invisible drops to another person and thereby infecting them.
It does not matter if someone appears sick or not. Asymptomatic transmission “is the Achilles’ heel of COVID-19 pandemic control through public health strategies,” according to an editorial May 28 in the New England Journal of Medicine. It said that SARS-CoV-1 is even more contagious than SARS-CoV-2.
The editors, by researchers Monica Gandhi, Deborah Yokoe and Diane Havlir at the University of California, San Francisco, referred to recent study of a coronavirus outbreak at a reputable nursing home that “strongly proves that our current approach is not enough. “
They said these symptoms include high genetic relative, transmission primarily via respiratory driplets, and the frequency of lower respiratory symptoms (short, cough, and shortness of breath), with both infections developing a median of five days after exposure.
This study from the University of California, San Francisco, found that there is a high viral load of SARS-CoV-2 contamination in the upper respiratory tract, even among pre-symptomatic patients, “which distinguishes it from SARS- CoV-1, where replication occurs mainly in the lower respiratory tract. ”
“Despite the deployment of similar control interventions, the trajectories of the two epidemics have run in dramatically different directions,” she added. “Within 8 months, SARS was monitored after SARS-CoV-1 had infected approximately 8,100 individuals in restricted geographical areas.”
Governments around the world are struggling to stop the spread of the pandemic. (An epidemic is a disease that infects regions as a community.) The “Spanish flu” of 1918-1919 and Black Death from 1347 to 1351 were two of the most extreme pandemics ever recorded.
As of Saturday, COVID-19, the disease caused by the SARS-CoV-2 virus, had infected at least 19.4 million people worldwide and 4.9 million in the US. It had killed more than 721,762 people worldwide and at least 161,365 in the US, according to data collected by Johns Hopkins University.
The stock market has been on a wild ride in recent months. The Dow Jones Industrial Index DJIA,
and the S&P 500 SPX,
crashed Friday when investors rounded two waits for a fiscal stimulus; the COMP of Nasdaq Composite,
7-winning streak some.
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