other COVID variants. However, Dominguez says, the odds of dead virus — and dead virus alone — triggering a positive antigen test in a human rather than a petri dish are low.
Unlike scientists in a lab, the human body in attack mode isn’t trying to inactivate viruses just so. It’s trying to obliterate them, proteins and all. “RNA can last longer than the proteins,” says Wroblewski, but neither substance is known for sturdiness. Even for scientists, it’s somewhat of an art to keep proteins intact after inactivating the virus.
“It is not easy,” says Dr. Izabela Ragan, a veterinary scientist at Colorado State University who has branched into human virology, and who has worked for about two years on developing a vaccine against SARS-CoV-2. Her work hinges on killing the virus while preserving the shape of its proteins.
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The confusion about how to interpret test results
The confusion around how to interpret test results stems largely from this conundrum: While there is a wealth of testing options available, there is no foolproof way to gauge whether a person is actually infectious.
“I wish there was,” Binnicker adds. “There is no test that we have for infectiousness.”
The best option is to take a patient’s sample, stick it in a dish of thriving living cells, and see what happens to the healthy cells. If there’s a live virus, according to Dirk Dittmer, a virologist at the University of North Carolina-Chapel Hill, “then the cells would die, just like the lung cells in your body would die.” But the finicky process takes about three days and can be done only in labs cleared to handle such pathogens, rendering it impractical.
Instead, the most widely available tests rely on totally different methods. They fall into two categories, typically called molecular tests and antigen tests.
Molecular tests, including PCR, look for specific bits of the virus’s RNA. With the exception of a few over-the-counter options, the tests are