“Due to the significance of asymptomatic and pre-symptomatic transmission, this guidance further reinforces the need to test asymptomatic persons, including close contacts of a person with documented SARS-CoV-2 infection,” the updated testing guidelines say.
The shift in testing protocols prompted concern from scientists and public health officials. Widespread testing of both symptomatic and asymptomatic individuals has been a cornerstone of the pandemic’s containment efforts.
“This walk back is a threat to public health and the gains we’ve made,” William Li, MD, a physician scientist in Cambridge, Massachusetts, tells Verywell.
Exceptions to the amended guidelines apply to healthcare workers and “vulnerable” populations, such as older people and people with underlying health conditions that put them at risk for severe disease.
Anthony Fauci, MD, the director of the National Institute of Allergy and Infectious Diseases, stated that he was not involved in the decision-making process, as he was undergoing a procedure to remove a polyp from his vocal cord when the CDC’s revisions went live.
Why Testing Widely Matters
Research has indicated that when a person is exposed to someone infected with COVID-19, they typically enter a brief presymptomatic period. The stage accounts for the window between exposure to SARS-CoV-2 (the virus that causes COVID-19) and the development of symptoms (if they develop any).
While the CDC’s updated guidelines downplay the importance of the presymptomatic stage, a study on the patterns of transmissibility demonstrated that 44% of SARS-CoV-2 infections stem from this phase.
“Significant presymptomatic transmission would probably reduce the effectiveness of control measures that are initiated by symptom onset, such as isolation, contact tracing, and enhanced hygiene or use of face masks for symptomatic persons,” the authors of the study, published in April in the journal Nature Medicine, write.
Presymptomatic people still carry a heavy viral load (the amount of a virus’ genetic material in a person’s system) even if they never develop symptoms. People can easily—and unknowingly—spread the virus to others, and health officials have no means to track or trace the root of the virus’ circulation.
Li, who is the president and medical director of the Angiogenesis Foundation, a disease prevention nonprofit, says that waiting to test until someone is very ill will lead to more severe disease developing in the community.
However, some people never develop COVID-19 symptoms at all. According to the CDC, 40% of infected individuals remain asymptomatic throughout the course of their infection.
“Asymptomatic people can be super spreaders, and by not testing them we are unable to spot the threat and contain it," Li says. “This is like reversing TSA airport security at the time of a known terrorist threat.”
CDC Change Clashes With Other Protocols
The World Health Organization (WHO) takes a different stance on COVID-19 testing. In a report titled “Laboratory testing for 2019 novel coronavirus (2019-nCoV) in suspected human cases,” the WHO states that the decision to test should be guided by the chances of infection, which is to be determined using both clinical and epidemiological information.
“PCR testing of asymptomatic or mildly symptomatic contacts can be considered in the assessment of individuals who have had contact with a COVID-19 case,” the report says.
In response to the CDC’s new guidelines, The American Public Health Association (APHA) released a statement on August 27 emphasizing that the revised approach could endanger lives.
“We are also concerned that this change was made without effective consultation with public health professionals who are on the ground managing this outbreak," APHA Executive Director George C. Benjamin, MD, said in the statement. “It makes the messaging confusing and may reduce access for those needing testing. Lack of access to adequate testing has been a significant barrier to getting effective disease control of this pandemic.”
The American Medical Association (AMA) released a statement on August 26 urging the CDC to not only rethink its decision but provide scientific justification for the modification.
“Suggesting that people without symptoms, who have known exposure to COVID-positive individuals, do not need testing is a recipe for community spread and more spikes in coronavirus,” AMA President Susan R. Bailey, MD, says in the statement.
The Infectious Disease Society of America (IDSA) called for the immediate reversal of the CDC’s revision in an August 26 statement, stressing the role that asymptomatic people play in the spread of SARS-CoV-2. The IDSA referenced its own diagnostic guidelines, which urge asymptomatic people with confirmed exposure to COVID-19 to get tested.
Consequences of Reduced Testing
Li emphasizes that the effect of confining testing to strictly symptomatic populations could have many ramifications for the U.S.—especially in educational institutions.
“As schools and colleges struggle to re-open, with communities of younger people who are more likely to be asymptomatic, this flip-flop on recommendations will make concerted efforts to get in-person education even more difficult, especially as many schools have taken on testing,” Li says.
Internationally, differences in testing protocols are reflected in the reduced COVID-19 transmission rates.
For example, South Korea prioritized testing for both asymptomatic and symptomatic people before the pandemic even reached its peak. The country implemented widespread testing in early February and has used the results to focus on quarantining all infected individuals and implement contact tracing.
In mid-March, the number of cases in South Korea had reached its apex, and the country had flattered its curve with no more than 600 cases a day.
The U.S. only started implementing testing measures in mid-March. By early April, the number of infected cases was 50 times higher than the numbers South Korea saw at its peak.
South Korea’s focus on mass testing for anyone exposed to the virus, regardless of symptoms, has been one of the main factors responsible for its ability to control the spread of the virus.
“Surveillance testing is what every country that has gotten a grip on the pandemic has used in combination with contact tracing,” Li says. “Testing is a critical part of control, and we absolutely need to make more testing available. All of these steps are needed to curb transmission so we can restore our society.”
In a special report published in the New England Journal of Medicine in July, scientists from the National Institutes of Health (NIH) announced an initiative to create a framework for more frequent and universal testing. The authors discussed the necessity of increasing the number of tests given to underserved populations, with the aim of creating 6 million cheap and rapid tests.
However, the CDC is not aligned with this goal, and is now reducing testing to a smaller population of people.
What Should You Do If You’re Exposed But Asymptomatic?
Even if you can’t get tested right away, you shouldn’t just wait it out if you believe you’ve been exposed to COVID-19, Li says.
“Whether or not [they have] symptoms, anyone who has had close contact with someone who is confirmed COVID-19-positive needs to get in touch with their doctor to seek advice on the need for testing and the need for quarantine or isolation,” he says. “Anyone who has close contact with an individual who is sick from active COVID-19 needs to take action.”
The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.
