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The spit also has trade-offs. While the virus appears to accumulate early in the saliva, later during infection the nose may be a better place to detect it.

Researchers at the California Institute of Technology have found that the virus is usually nailed first in spit, ultimately rising to higher levels on the nose. Their results show that highly sensitive tests such as PCR tests can detect infections in saliva days before nasal swabs, but less sensitive tests such as antigen tests may not.

Some experts noted that data on saliva is still mixed.

D., an infectious disease physician and clinical microbiologist at Rush University Medical Center in Chicago. “There are a few studies that I find really interesting,” said Mary K. Hayden.

However, Dr. Hayden said he interpreted the new studies cautiously, as “years, decades” of research suggested that nasopharyngeal samples are best for detecting respiratory viruses.

Some scientists also have practical concerns. The mouth is “a slightly more uncontrolled environment than the nasal passages,” said Joseph DeRisi, a biochemist at the University of California, San Francisco, president of the Chan Zuckerberg Biohub and author of the cheek swab paper. . “Did you drink Coke right before you took the test? The pH will be different. And these things are important.”

Director of the clinical virology laboratory at Yale New Haven Hospital, Dr. In an email, Marie-Louise Landry said saliva can be “viscous and difficult to work with,” especially when patients are sick and dehydrated.

After all, different approaches may be required in different situations. Dr. Hansen suggested that nasal swabs might be a good choice for people who have had symptoms for a few days, while saliva might be best suited for large-scale surveillance screening of asymptomatic people. “We need to get the right test to the right places,” he said.