AP

Reports suggest many have had coronavirus with no symptoms

Apr 20, 2020, 5:32 AM
FILE - In this Friday, April 10, 2020, file photo, amid coronavirus concerns, a healthcare worker t...
FILE - In this Friday, April 10, 2020, file photo, amid coronavirus concerns, a healthcare worker takes the temperature of a visitor to Essentia Health who was crossing over a skywalk bridge from the adjoining parking deck, in Duluth, Minn. A flood of new research suggests that far more people have had the novel coronavirus without any symptoms, fueling hope that it will turn out to be much less lethal than originally feared. While that’s clearly good news, it also means it’s impossible to know who around you may contagious, since people who don’t feel sick can still carry and spread the bug. (Alex Kormann/Star Tribune via AP, File)
(Alex Kormann/Star Tribune via AP, File)

A flood of new research suggests that far more people have had the coronavirus without any symptoms, fueling hope that it will turn out to be much less lethal than originally feared.

While that’s clearly good news, it also means it’s impossible to know who around you may be contagious. That complicates decisions about returning to work, school and normal life.

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

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

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

Collectively, though, they suggest “we have just been off the mark by huge, huge numbers” for estimating total infections, he said.

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

STEALTH CASES

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

Scientists in Iceland screened 6% of its population to see how many had previously undetected infections and found that about 0.7% tested positive. So did 13% of a group at higher risk because of recent travel or exposure to 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 New York, a hospital tested all pregnant women coming in to deliver over a two-week period. Nearly 14% of those who arrived with no symptoms of coronavirus turned out to have 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 nearly half who tested positive had no symptoms at the time. Researchers estimate that 18% of infected people never developed any.

FLAWED METHODS

These studies used tests that look for bits of the virus from throat and nose swabs, which can miss cases. Someone can test negative one day if there’s not much virus to detect and then positive the next.

Symptoms also may not appear when someone is tested but turn up later. One Japanese study found more than half of those who had no symptoms when they tested positive later felt sick.

Better answers may come from newer tests that check blood for antibodies, substances the immune system makes to fight the virus. But the accuracy of these, too, is still to be determined.

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

The work has not been formally published or reviewed, but some scientists were quick to question it. Participants were recruited through Facebook ads, which would attract many people likely to be positive who have had symptoms and want to know if the coronavirus was the reason. Some neighborhoods also had way more participants than others, and “hot spots” within the county might have made infections seem more common than they are elsewhere.

Ships, maternity wards and single counties also don’t provide data that can be used to generalize about what’s happening elsewhere. And many of the figures have come from snapshots, not research on wide populations over time.

NEXT STEPS

Antibody testing in particular needs to be done “in an unbiased approach” on groups of people that are representative of the geographic, social, racial and other conditions, Mina said.

The CDC and other groups plan such studies, and they could guide public health advice on returning to normal life for people in certain areas.

If infections are more widespread than previously understood, it’s possible that more people have developed some level 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 learn about whether mild illnesses confer immunity and how long it might last.

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

“If they’ve all seen the virus before, then maybe you can relax in that neighborhood” and ease social distancing, Mina said. “We’re not anywhere close where we need to be” on antibody testing to do that yet, he said.

___

AP writers Mike Stobbe in New York and Robert Burns and Lolita Baldor in Washington contributed to this report.

___

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

___

Follow AP coverage of the virus outbreak at https://apnews.com/VirusOutbreak and https://apnews.com/UnderstandingtheOutbreak.

Today’s Top Stories

AP

Dozens of mourners gather for a vigil near Central Avenue and St. Johns Avenue in downtown Highland...
By MICHAEL TARM, KATHLEEN FOODY and STEPHEN GROVES Associated Press

Police: Parade shooting suspect contemplated 2nd shooting

The suspect in the Highland Park parade shooting confessed to police that he fired on the crowd, a prosecutor said Wednesday.
22 hours ago
This June 5, 2013, image provided by the California Department of Water Resources shows a drip irri...
JESSICA DAMIANO Associated Press

Tips for growing a healthy garden during drought

Watering needs for plants could increase during periods of extreme heat, when the soil dries out more quickly.
2 days ago
Two members of the FBI move items from the scene at the Highland Park shooting...
MICHAEL TARM, KATHLEEN FOODY and STEPHEN GROVES Associated Press

Police: Gunman fired more than 70 rounds at July 4 parade, 7 dead

Police gave no motive for the attack in Highland Park, an affluent community of about 30,000 on Chicago's north shore.
2 days ago
Frankfurter-munching phenom Joey “Jaws” Chestnut has gobbled his way to a 15th win at the Natha...
By JENNIFER PELTZ and JULIA NIKHINSON Associated Press

Joey Chestnut is chomp champ again in July 4 hot dog contest

NEW YORK (AP) — Frankfurter-munching phenom Joey “Jaws” Chestnut put a protester in a chokehold while gobbling his way to a 15th win Monday at the Nathan’s Famous Fourth of July hot dog eating contest, powering down 63 hot dogs and buns at the annual exhibition of excess. In a decisive chowdown comeback, women’s record-holder […]
3 days ago
FILE - Fireworks explode over Baltimore's Inner Harbor during the Ports America Chesapeake 4th of J...
BOBBY CAINA CALVAN ASSOCIATED PRESS

A turbulent US this July 4, but many see cause to celebrate

July 4 has arrived as many citizens struggle to find a reason to celebrate. Yet many also see cause for celebration, including President Joe Biden.
3 days ago
A Navy soldier stands guard as authorities wait for the arrival of people who were evacuated from t...
Associated Press

Tropical Storm Colin brings rain to Carolinas, weakens

Tropical Storm Colin formed along the coast on Saturday. Conditions are expected to improve by Monday's Fourth of July celebrations.
4 days ago

Sponsored Articles

Tax Harassment...
Jordan Wilcox

The best strategies for dealing with IRS tax harassment | You have options!

Learn how to deal with IRS tax harassment. This guide will teach you how to stop IRS phone calls and letters, and how to handle an IRS audit.
spend a day at Bear Lake...
Bear Lake Convention and Visitors Bureau

You’ll love spending the day at Bear Lake | How to spend a day at Bear Lake

Bear Lake is a place that needs to be experienced. Spend a day at Bear Lake.
Curb Appeal...
Price's Guaranteed Doors

How to have the best of both worlds for your house | Home security and curb appeal

Protect your home and improve its curb appeal with the latest security solutions like beautiful garage doors and increased security systems.
Prescription opioids can be disposed of during National Prescription Take Back Day...
Know Your Script

Prescription opioid misuse | How to protect your family from the opioid epidemic

Studies have shown that prescription opioid misuse has increased since COVID-19. So what do you need to know about these opioids?
national heart month...
Intermountain Healthcare

National Heart Month: 5 Lifestyle Changes to Make Today to Keep You Heart Healthy

Heart disease is the leading cause of death for both men and women. One person dies every 36 seconds in the United States from cardiovascular disease
Joseph Smith Memorial Building...
Temple Square

The Joseph Smith Memorial Building is an icon of Salt Lake City | Why hosting an event at this beautiful location will make you a hero this year

Here's why hosting an event at the iconic Joseph Smith Memorial Building in downtown Salt Lake City will make you a hero this year.
Reports suggest many have had coronavirus with no symptoms