Cold, flu, flu shot won’t cause positive virus test
Numerous users on social media have claimed that coronavirus tests are inaccurate and ineffective and encouraged their followers not to take or trust them.
“A positive test for COVID-19 only means you have antibodies for the flu and/or the common cold,” reads a post on Instagram. “DONT TAKE THE TEST!”
“Stop testing yourselves!!! If you’ve had a cold (coronavirus) you will test positive for COVID 19. If you’ve had the flu. You will test positive for COVID. If you’ve been vaccinated for influenza, you will test positive for COVID,” reads a post on Facebook.
The users behind the posts did not respond to requests from USA TODAY for comment.
The common cold and coronavirus tests
This isn’t the first time internet users have alleged a link between the cold and positive coronavirus tests. USA TODAY debunked a similar claim in July.
The claim that the common cold will produce a positive coronavirus test relates to antibody tests.
Those check the blood for antibodies – diseasespecific proteins produced by white blood cells to fight a virus – and reveal whether an individual had a past infection.
According to the Centers for Disease Control and Prevention, “a positive test result shows you may have antibodies from an infection with the virus that causes COVID-19. However, there is a chance that a positive result means you have antibodies from an infection with a different virus from the same family of viruses (called coronaviruses).”
It’s true that the common cold is in the coronavirus family.
Lee Riley – head of the Division of Infectious Disease and Vaccinology at the University of California-Berkley – confirmed to USA TODAY that “about a third of the common cold is caused by coronavirus strains that are distinct from the COVID-19 coronavirus.”
Still, he said, it’s unlikely that having contracted the common cold would result in a positive test for COVID-19 antibodies.
“These common cold coronavirus strains would not induce an antibody response high enough to be mistaken for the antibody response against the COVID-19 virus,” he wrote in an email. “If they did, almost everyone on the planet would be shown to have an antibody against COVID-19.”
Antibody tests are not intended for diagnostic purposes. Diagnoses are based on viral tests.
According to the Food and Drug Administration, there are two kinds of viral tests for coronavirus that can be used for diagnostic purposes: molecular tests and antigen tests.
Molecular tests detect the virus’s genetic material, and antigen tests detect specific proteins from the virus.
COVID-19 is caused by a specific type of coronavirus with distinct genetic material and proteins.
That’s why the CDC notes on its site that “other coronaviruses cannot produce a positive result on a viral test for SARS-CoV-2.”
The flu and COVID-19 tests
Though some symptoms of the flu and coronavirus are similar, the viruses are distinct. The flu is caused by an influenza virus, not a coronavirus.
Riley told USA TODAY that claims about the flu and coronavirus tests are “nonsensical.”
“The influenza virus is very different from the COVID-19 virus and would never induce an antibody response that would be mistaken for the COVID-19 virus antibody,” he wrote.
Flu vaccines do not contain any types of coronaviruses, according to WUSA9.
A spokesperson for the FDA told FactCheck.org that all FDA-authorized tests for coronavirus are specifically checked for cross-reactivity with influenza virus. They have not observed cross-reactivity with any of the tests.
Our rating: False
Viral tests for coronavirus detect its distinct genetic material or proteins – so other viruses won’t cause false positives. It’s possible that the common cold will produce a positive result in an antibody test, but those aren’t used to diagnose COVID-19.