"Broad testing" of people for the coronavirus as was done in South Korea could significantly slow the spread of the disease in parts of the United States that now have relatively few cases of COVID-19, an infectious diseases expert said Tuesday.
But it remains to be seen whether enough reliable coronavirus tests and sufficient supplies of related equipment can be deployed in those regions, which include large swaths of the Western U.S., quickly enough to flatten the disease's upward curve there.
South Korea has been lauded for knocking down a COVID-19 outbreak after employing an aggressive strategy of testing more than 440,000 people for the virus, along with other mitigation measures.
The United States currently is engaged in an emergency effort to "flatten the curve," or the rate of increase in new COVID-19 cases, in order to avoid overwhelming the capacity of hospital systems and to lower the death rate from the virus.
Dr. Angela Caliendo said Tuesday that South Korea's experience "shows you the importance of testing."
"I do think the testing they did in South Korea was very important in controlling their outbreak," said Caliendo, an infectious diseases professor at Brown University's Alpert Medical School.
With their widespread testing program, South Korean authorities were able to identify infected people, isolate them and trace their contacts with other people, who then also could be tested.
If the United States had adequate testing, "you could consider areas of the country that are at different points of the virus" spread progression, Caliendo said during a call with reporters arranged by the Infectious Diseases Society of America.
And if those areas' residents received "more broad testing" than the levels seen elsewhere in the U.S. "you could imagine where you would mimic, in some regions at least" the experience of South Korea in suppressing the spread of COVID-19, she said.
"There are areas in this country that have not been hit" to the same extent as other areas, she noted.
Caliendo said that South Korea benefited from having several companies that produce chemical reagents used in virus testing.
Getting broad-based testing of Americans could take some time.
Dr. Kimberly Hanson, a professor of pathology at the University of Utah School of Medicine, said on the conference call that currently, unlike the early days of the outbreak in the U.S., there are about two dozen types of coronavirus tests available for rapidly screening people.
"Our goal is to test everybody who has symptoms in the community," Hanson said. "We don't have enough testing right now where we are able to test everybody who is symptomatic, but we are ramping up really well."
But in the meantime, she said, "The main limitation we're facing now is actually having shortages of other pieces around the tests themselves," such as swabs and tubes to collect samples.
"We've faced some serious shortages of swabs," Hanson said. "We have colleagues who are faced with shortages of the reagents."
Hanson also noted that states that have been "hotbeds" of COVID-19 outbreaks are seeking more testing done than elsewhere. Data reviewed by CNBC shows wide variations in the amount of tests per capita throughout the U.S.
A number of states that could, as Caliendo suggested, see a lower outbreak curve if they adopted a South Korea-type testing regimen are among those states with the lowest number of tests per capita currently.
Both Hanson and Caliendo mentioned the need to improve the quality of testing.
"Overall, what we have on our hands right now are good tests, but no test is perfect," Caliendo said.
And she noted that the level of experience of the person performing the test can affect the specimen quality
The doctors said it will be particularly important to improve serological tests, which can reveal whether people who do not have symptoms of COVID-19 have developed antibodies for the disease, and who could transmit the virus to others. Results of serological tests take longer than rapid tests.
"Ideally, we're going to need to couple acute diagnoses" from rapid screening tests "with serologic testing," Hanson said.
"Because they will give us an idea of who is left in our community who is at risk of developing an infection," she said.
She said that having a clear picture of how many people are carrying the virus "will be very important to determining" by the fall and winter "where we need to limit people's social interactions."
Caliendo said there "are are a couple of" serological tests approved on an emergency use basis by the U.S. Food and Drug Administration "right now."
But, she added, "We don't know how well they perform."
Caliendo pointed out that "typically, antibodies take a week or so to form."
"You will have patients who have infections ... but who do not have antibodies" that would show up when they are tested, Caliendo said.
That means tests performed in later weeks of infections might be better at assessing overall infection rates.
Hanson added that another factor to consider is the open question of whether a person who has developed antibodies to COVID-19 can develop the disease again.
"We still need to work out what developing an antibody response means, whether it's protective or not," Hanson said.
During a news conference Tuesday, New York Gov. Andrew Cuomo, whose state currently has the most number of COVID-19 cases in the U.S., emphasized the need to improve rapid testing capacity so that New York and surrounding states can start returning to normal life.
"You have to have that testing, and you have to have that testing on scale," Cuomo said, referring to the types of tests that can determine whether someone has the coronavirus within 15 minutes.
"We have about a 50,000-person testing capacity, which is nice but not of a scale that's going to make a large difference."
He said that no single private company currently has the capacity to produce enough rapid coronavirus tests to satisfy the number that will need to be done.
Cuomo encouraged companies that might be able to increase their capacity to contact New York state's Empire Development Corp., which is willing to fund companies for that effort.
Cuomo also said that the New York state Health Department has developed and approved testing for coronavirus antibodies, but added that such testing capacity has to be increased.
-- Additional reporting by Noah Higgins-Dunn.