Sticky mucus may thwart alcohol-based
hand sanitizers’ ability to fight the flu.
Flu viruses encased in mucus drops from
infected people’s spit can withstand the alcohol in hand
sanitizers for more than two minutes, researchers report September 18 in mSphere. Researchers dotted volunteers’
fingers with either mucus or saline solution containing the flu virus, then
measured how long it took to inactivate the virus in both wet and dry samples.
A five-microliter drop — about the size
of a pinhead — of mucus-coated flu virus took more than half an hour to dry,
almost twice as long as saline. Drying time was important because previous
studies tested sanitizers’ killing ability on dry viruses, and didn’t account
for mucus’s moistening power.
A hand sanitizer containing 31 percent
alcohol inactivated flu viruses in saline solution within 20 seconds. And in
already dried mucus, that process took just under eight seconds. But moist mucus
shielded flu viruses from alcohol, keeping the viruses viable for up to 2
minutes and 39 seconds, Ryohei Hirose, an infectious disease researcher at the Kyoto
Prefectural University of Medicine in Japan, and his colleagues found. That may
be long enough for health care workers to unwittingly transfer virus-infected
mucus from one person to another.
The team didn’t test whether rubbing the
sanitizer over the skin causes the alcohol to penetrate the mucus and kill
viruses faster, Hirose says. Rubbing might help, he acknowledged. But there’s already
an easy way to kill flu viruses: Washing hands with plain water or with soap
killed viruses within 30 seconds, even when the mucus was still wet.