“How common is it for people to contract and fight off
viruses without knowing it?
“In general, having an infection without any symptoms is
common. Perhaps the most infamous example was Typhoid Mary, who spread typhoid fever to
other people without having any symptoms herself in the early 1900s. My
colleagues and I have found that many infections are fought off by the body
without the person even knowing it.
“For example, when we carefully followed children for
infection by the parasite Cryptosporidia, one
of the major causes of diarrhea, almost
half of those with infections showed no symptoms at all. In the case
of the flu, estimates are that anywhere
from 5% to 25% of infections occur with no symptoms. For the
most part, symptoms are actually a side effect of fighting off an infection. It
takes a little time for the immune system to rally that defense, so some cases
are more aptly considered pre-symptomatic rather
than asymptomatic.
“How can someone spread coronavirus if they aren’t coughing
and sneezing?
“Everyone is on guard against the droplets that spray out from a
coronavirus patient’s cough or sneeze. They’re a big reason public health
officials have suggested everyone should wear masks. But the virus also spreads
through normal exhalations that can carry tiny
droplets containing the virus. A regular breath may spread the virus several
feet or more. Spread could also come from fomites –
surfaces, such as a doorknob or a grocery cart handle, that are contaminated
with the coronavirus by an infected person’s touch.
“What’s known about how contagious an asymptomatic person
might be?
“No matter what, if you’ve been exposed to someone with
COVID-19, you should self-quarantine for the entire 14-day incubation period. Even if
you feel fine, you’re still at risk of spreading the coronavirus to others.
Most recently it has been shown that high levels of the virus are present in
respiratory secretions during the “pre-symptomatic”
period that can last days to more than a week prior to the
fever and cough characteristic of COVID-19. This ability of the virus to be
transmitted by people without symptoms is a major reason for the pandemic.
“After an asymptomatic infection, would someone still have
antibodies against SARS-CoV-2 in their blood?
“Most people are developing antibodies after recovery from
COVID-19, likely even those without symptoms. It is a reasonable assumption,
from what scientists know about other coronaviruses, that those antibodies will
offer some measure of protection from reinfection. But nothing is known for sure yet. Recent
sero surveys in New York City that check people’s blood for antibodies against
SARS-CoV-2 indicate that as many as one in five residents may have been
previously infected with COVID-19. Their immune systems had fought off the
coronavirus, whether they’d known they were infected or not – and many
apparently didn’t.
“How widespread is asymptomatic COVID-19 infection?
“No one knows for sure, and for the moment lots of the
evidence is anecdotal. For a small example, consider
the nursing home in Washington where many residents became
infected. Twenty-three tested positive. Ten of them were already sick. Ten more
eventually developed symptoms. But three people who tested positive never came
down with the illness. When doctors tested 397 people staying at a homeless
shelter in Boston, 36% came up positive for COVID-19 –
and none of them had complained of any symptoms.
“In the case of Japanese citizens evacuated from Wuhan, China
and tested for COVID-19, fully 30% of those infected were asymptomatic. An
Italian pre-print study that has not yet been peer-reviewed found that 43%
of people who tested positive for COVID-19 showed no symptoms.
Of concern: The researchers found no difference in how potentially contagious
those with and without symptoms were, based on how much of the virus the test found in
individuals’ samples.
“The antibody sero surveys getting underway in different parts of the country add further evidence that
a good number – possibly anywhere from around 10% to 40% – of those infected
might not experience symptoms. Asymptomatic SARS-CoV-2 infection appears to be
common – and will continue to complicate efforts to get the pandemic under
control” (The Conversation).
William Petri is a professor of
medicine and microbiology at the University of Virginia who
specializes in infectious diseases. Here, he runs through what’s known and what
isn’t about asymptomatic cases of COVID-19.
In Today's News:
ReplyDelete"Government orders 100,000 new body bags as Trump minimizes death toll. Federal coronavirus response documents obtained by NBC News suggest that the president's optimism about 'Opening Up America' is at odds with dire warnings from inside his administration"
"The federal government placed orders for well over 100,000 new body bags to hold victims of COVID-19 in April, according to internal administration documents obtained by NBC News, as well as public records. The biggest set was earmarked for purchase the day after President Donald Trump projected that the U.S. death toll from the coronavirus might not exceed 50,000 or 60,000 people..." (NBC).
Right now Covid-19 deaths in America are at 64,000+
From Richard Palzer:
ReplyDelete"So, given the risk of asymptomatic people being infected and passing it on to others, what--seriously and realistically--is to be done? Is there no safe way to open the economy at all? With people's livelihoods lost and the already vulnerable's poverty exacerbated, their ranks increased (their misery not really appreciating the company), what's the recommended path toward solution? Do we all just quarantine, shutting down the global economy, and ask the government--ultimately saddling future generations ad infinitum--to bear the cost of our exponentially increasing national debt? If there's a Dr. Fauci recommendation, we need to listen--let's follow the science. I'd like, with the same confidence in his science and pragmatism, to trust his judgment--i.e., reason over ideology."