Reports suggest many have had coronavirus without symptoms

A flood of new research shows that far more people experienced the coronavirus without the symptoms, fueling hope that it'll grow to be significantly less lethal than originally feared.

While that's clearly very good news, in addition, it means it's impossible to know who around you could be contagious. That complicates decisions about time for work, school and normal life.

In the last week, reports of silent infections attended from a homeless shelter in Boston, a U.S. Navy aircraft carrier, pregnant women at a New York hospital, several Europe and California.

The top of the U.S. Centers for Disease Control and Prevention says 25% of infected people might possibly not have symptoms. The vice chairman of the Joint Chiefs of Staff, Gen. John Hyten, thinks it can be as high as 60% to 70% among military personnel.

None of the numbers can be fully trusted because they're predicated on flawed and inadequate testing, said Dr. Michael Mina of Harvard's School of Public Health.

Collectively, though, they advise "we've just been off the mark by huge, huge numbers" for estimating total infections, he said.

Worldwide, a lot more than 2.3 million infections and a lot more than 160,000 deaths have been confirmed. The virus has caused practically unprecedented economic and social harm since its existence was reported in early January.

STEALTH CASES

Predicated on known cases, health officials have said the virus usually causes mild or moderate flu-like illness. Now evidence keeps growing that a substantial number of individuals may have no symptoms at all.

Scientists in Iceland screened 6% of its population to observe how many had previously undetected infections and discovered that about 0.7% tested positive. So did 13% of an organization at higher risk as a result of recent travel or contact with someone sick.

Aboard the aircraft carrier USS Theodore Roosevelt, where one crew member died from the virus, "the rough numbers are that 40 percent are symptomatic," said Vice Adm. Phillip Sawyer, deputy commander of naval operations. The ratio may change if more develop symptoms later, he warned.

In NY, a hospital tested all pregnant women coming in to provide over a two-week period. Nearly 14% of these who arrived without symptoms of coronavirus proved to own it. Of the 33 positive cases, 29 had no symptoms when tested, although some developed them later.

Previously, tests on passengers and crew from the Diamond Princess cruise ship found almost half who tested positive had no symptoms at that time. Researchers estimate that 18% of infected people never developed any.

FLAWED METHODS

These studies used tests that search for items of the virus from throat and nose swabs, that may miss cases. Someone can test negative 1 day if there's very little virus to detect and then positive the next.

Symptoms also might not appear when someone is tested but arrive later. One Japanese study found over fifty percent of those who had no symptoms if they tested positive later felt sick.

Better answers will come from newer tests that check blood for antibodies, substances the immune system makes to fight the virus. However the accuracy of the, too, continues to be to be determined.

On Friday, researchers reported results from antibody tests on 3,300 persons in California's Santa Clara county: Between 1.5% and 2.8% have already been infected, they claimed. That would mean 48,000 to 81,000 cases in the county - a lot more than 50 times the number which have been confirmed.

The work has not been formally published or reviewed, however, many scientists were quick to question it. Participants were recruited through Facebook ads, which would attract many persons apt to be positive who've had symptoms and wish to know if the coronavirus was the reason why. Some neighborhoods also had way more participants than others, and "hot spots" within the county may have made infections seem more prevalent than they are elsewhere.

Last week, Los Angeles County and University of Southern California researchers released preliminary, partial results from a similar effort utilizing a rapid antibody test at six drive-through sites. Predicated on results from 863 people, they estimate that 4% of adults in the county experienced the virus. However the small sample size and other variables including test accuracy mean the rate could be anywhere from 2.8% to 5.6%, if more study confirms it. The results have not been published or reviewed by other scientists.

Studies like they are bound to find far more persons were infected than confirmed case tallies, because diagnostic testing shortages have caused many infections to go uncounted.

But ships, maternity wards and single counties don't provide data that works extremely well to generalize about what's happening elsewhere. And several of the figures have come from snapshots, not research on wide populations as time passes.

NEXT STEPS

Antibody testing in particular should be done "in an unbiased approach" on groups of individuals that are representative of the geographic, social, racial and other conditions, Mina said.

The CDC and other groups plan such studies, plus they could guide public health advice on time for normal life for folks in certain areas.

If infections are more widespread than previously understood, it's possible that more people are suffering from some degree of immunity to the virus. That could stifle the spread through what's called herd immunity, but scientists caution that there is still much to understand about whether mild illnesses confer immunity and how long it could last.

It will oftimes be months before enough reliable testing has been done to answer those questions and others, including how widespread infections have already been and the virus's true mortality rate, which includes only been estimated so far.

"If they've all seen the virus before, then maybe you can relax for the reason that neighborhood" and ease social distancing, Mina said. "We're not anywhere close where we need to be" on antibody testing to achieve that yet, he said.

© Copyright 2020 The Associated Press. All rights reserved. This material might not be published, broadcast, rewritten or redistributed without permission.