A South Korean soldier wearing a banner reading "Covid-19 Free" and a protective mask stands at a temperature screening point at Incheon International Airport in Incheon, South Korea, on Monday, March 9, 2020. SeongJoon Cho | Bloomberg | Getty Images

"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.