This is when people with COVID-19 are most contagious



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The number of coronavirus cases currently exceeds 21 million worldwide, according to the latest data aggregated by the Center for Systems Science and Engineering at Johns Hopkins University, but the actual number of cases is likely much higher.

The Centers for Disease Control and Prevention estimates that 40% of people with COVID-19 are in fact asymptomatic, making it difficult for healthcare professionals to trace transmission.

Other data suggests that 16% of coronavirus transmission is from carriers showing no symptoms or showing only very mild symptoms who, although contagious, may not believe they have the disease. .


Knowing when an infected person can spread SARS-CoV-2 is just as important as how the virus is spreading so quickly.

A case study from the quarantined Italian town of Vò published in the peer-reviewed journal Nature in June found that more than 40% of COVID-19 infections did not show any symptoms.

With a population of around 3,200 people, Vò reported the first COVID-related death in Italy on February 20. As a result, the townspeople were placed in quarantine for 14 days.

About 2.6% of the city tested positive for SARS-CoV-2, the virus that causes COVID-19, at the start of the lockdown, but that figure fell to 1.2% after a few weeks. During this entire period, 40% of these infections were in people who had no symptoms. The researchers also concluded that it took 9.3 days for people who tested positive to be free from the virus.

“A person with an asymptomatic infection is completely unaware of the carrier of the virus and, depending on their lifestyle and profession, could meet a large number of people without changing their behavior,” found the study, which was conducted by researchers from Imperial College London and the University of Padua.

“If we find a number of symptomatic people who test positive, we expect the same number of asymptomatic carriers who are much more difficult to identify and isolate,” according to Enrico Lavezzo, professor in the Department of Molecular Medicine at the University of Padua.

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This, according to medical professionals, raises questions about the contagion after contracting the virus and how long it remains.

Knowledge when just as important as how the virus spreads so quickly is how infected a person can spread SARS-CoV-2. The WHO recently released a science note on how the virus is spread, especially among those who do not have symptoms.

The virus can be detected in people one to three days before symptoms appear, with viral loads highest around the day of symptom onset, followed by a gradual decline over time, depending on the patient. World Health Organization.

This level of contagiousness appears to be one to two weeks for asymptomatic people, and up to three weeks or more for patients with mild to moderate illness. “Preliminary data suggests that people may be more contagious when symptoms appear than later in the disease,” he added.


The virus can be detected in people one to three days before their symptoms, with the highest viral loads on the first day.

“Transmission of SARS-CoV-2 can occur through direct, indirect or close contact with people infected with infected secretions such as saliva and respiratory secretions or their respiratory droplets, which are expelled when an infected person coughs, sneeze, talk or sing, ”WHO added. This makes asymptomatic transmission all the more prevalent, scientists say.

However, all studies in asymptomatic people have limitations, the WHO added: “For example, some studies do not clearly describe how they followed asymptomatic people at the time of testing to determine if they have already developed symptoms. Others have defined the term “asymptomatic” very narrowly as people who have never developed a fever or respiratory symptoms, rather than those who have not developed any symptoms.

The death toll from COVID-19 in the United States could reach nearly 300,000 by December 1, but wearing a mask constantly from today could save around 70,000 lives, according to the Institute for Health Metrics and Evaluation (IHME) from the School of Medicine at the University of Washington.

“It seems people wear masks and socially distance themselves more frequently as infections increase, then after a while as infections drop people let their guard down and stop taking these steps to protect themselves and protect themselves. the others, ”said Christopher Murray, Director of IHME.

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California Governor Gavin Newsom a Democrat last month announced a rollback of statewide operations at restaurants as well as bars, zoos, wineries, museums, card rooms and cinemas. “It’s in all counties in the state of California, not just those on the watch list,” he said.

The shutdown also affected the indoor operations of gymnasiums, places of worship, offices for non-critical sectors, hairdressers, beauty salons, indoor malls and other places of business in 30 counties listed on the California “watch list”, which makes up 80% of the state of California.

On the anniversary of the 1918 flu, health writer Ed Yong warned of yet another pandemic and now says the United States must learn the lessons of the past seven months, adding: “COVID-19 is just a harbinger of the worst plagues to come.”


New York, the epicenter of the pandemic in the United States, was a case study of how the virus is transmitted.

“Despite numerous warnings, the United States has squandered every possible opportunity to control the coronavirus. And despite its enormous benefits – immense resources, biomedical power, scientific expertise – it has failed, ”he wrote in the September issue of The Atlantic.

While South Korea, Thailand, Iceland, Slovakia and Australia have acted “decisively” to flatten and then bend the curve of new infections down, “the United States has only achieved ‘a plateau in the spring, which turned into an appalling upward slope in the summer, “he added.

Yong said he had spoken to more than 100 health experts since the start of the pandemic and sums up the US mistakes thus: “A slow response from a government stripped of expertise has allowed the coronavirus to take hold. foot “, aggravated by” chronic underfunding of public health. ”

“A bloated and inefficient health care system left hospitals ill-prepared for the wave of illness that followed. The racist policies that have endured since the days of colonization and slavery have made Indigenous and black Americans particularly vulnerable to COVID-19, ”he added.

New York, the former American epicenter of the pandemic, was a case study of how some Americans fared better than others and how the virus was transmitted. Blacks and Latin Americans were hospitalized twice as many as Caucasians at the height of the crisis, according to data released in May by the city.

Black New Yorkers were hospitalized at a rate of 632 per 100,000 people, while Caucasians were hospitalized at a rate of 284 per 100,000 people. Black and Hispanic residents were dying at a rate of 21.3 per 100,000, while non-white races were dying at a rate of 40.2 per 100,000, the data showed.

One theory: More foreign-born Americans are likely to live in multigenerational households, and Asians and Hispanics are more likely than whites to be immigrants, according to the Pew Research Center. People of color are more likely to work in frontline jobs that carry a greater risk of contracting COVID-19.

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Earlier this month, President Donald Trump sidestepped lawmakers across the country as he demanded the power to defer payroll taxes and replace an expired unemployment benefit with a lower amount after negotiations with Congress failed. on a new coronavirus rescue plan.

However, the executive decree and memoranda ostensibly providing relief amid the intractable pandemic appear neither feasible nor legal, analysts said, adding that the wording of the decrees raised more questions than answers.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and a member of the White House Coronavirus Task Force, has been optimistic about a vaccine coming in late 2020 or early in 2021, and said people should continue to practice social distancing and wearing masks.

Fauci said he hoped a vaccine for the coronavirus could be developed by early 2021, but previously said a vaccine was unlikely to provide 100% immunity; he said the best realistic result, based on other vaccines, would be 70% to 75% effectiveness. Other epidemiologists are even more wary of a vaccine that will wipe out transmission of the virus anytime soon.

Coronavirus Update: COVID-19 has now killed at least 771,276 people worldwide, and the United States ranks 10th in the world for deaths per 100,000 people (51.5), according to Johns Hopkins University. On Sunday, the United States has the highest number of confirmed COVID-19 cases (5,361,302) and deaths (169,483) in the world. Globally, the confirmed cases now number 21,261,598.

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