How long could someone be contagious before testing positive for COVID-19 ?
How long could someone be contagious before a positive coronavirus test?
Studies
have shown that people may be contagious for about two days before developing
COVID-19 symptoms.
In
fact, right before developing symptoms is when people are likely the most
contagious, said Dr Werner Bischoff, an infectious disease specialist at Wake
Forest University.
People
who never develop symptoms can spread infection, too. That’s a problem because
many people would never seek testing unless they developed symptoms or knew they’d
been exposed.
But
there’s a more complicated part to this question: What if someone knows they
were exposed but their virus test comes back negative — could they still be
contagious?
Maybe.
A
negative test within less than seven days after exposure “is a very, very poor
indicator of whether you have virus on board,” said Dr Alan Wells of the
University of Pittsburgh Medical Center.
Some
tests are less accurate than others, and you have to factor in the incubation
period, he said.
A
negative test between seven and 10 days of exposure is a better indicator,
Wells said, but even then some people might not test positive until later.
“That
is why if you have had a credible exposure, you should wear a mask and you
should self-quarantine if there’s any question,” he said.
