NEWS1294 20 MARCH 2020 • VOL 367 ISSUE 6484 SCIENCEPHOTO: JEFFERSON BERNARDES/AFP/GETTY IMAGESFEATURES
Dozens of diseases
wax and wane
with the seasons.
Will COVID-19?
SICK
TIME
O
n a December afternoon, 13 days
before the winter solstice, six
men and women checked into the
Surrey Clinical Research Facil-
ity, part of the University of Sur-
rey in the United Kingdom. After
having their noses swabbed to
check for 16 different respiratory
viruses, they walked into their own
temperature-regulated rooms and, for
24 hours, stayed in a semirecumbent posi-
tion in dim light. Nurses placed a cannula
into a vein of each person’s arm, allowing
easy sampling of blood that flowed through
a tube to portals in the wall. The six subjects
could press buzzers for bathroom breaks,
where the stool and urine were collected, but
otherwise, they were alone in the near-dark.
None of these people were sick. And al-
though the shortest day of the year was ap-
proaching, their ritual had nothing to do
with pagan rites, Yuletide traditions, or the
annual hippie gathering at nearby Stone-
henge to celebrate the rebirth of the Sun.Instead, they were paid volunteers in a study
led by infectious disease ecologist Micaela
Martinez of Columbia University to investi-
gate a phenomenon recognized 2500 years
ago by Hippocrates and Thucydides: Many
infectious diseases are more common during
specific seasons. “It’s a very old question, but
it’s not very well studied,” Martinez says.
It’s also a question that has suddenly
become more pressing because of the
emergence of coronavirus disease 2019
(COVID-19), which has now infected more
than 175,000 people around the globe. Some
hope the disease might mimic influenza and
abate as summer arrives in temperate re-
gions of the Northern Hemisphere, where
about half of the world’s population lives.
U.S. President Donald Trump has expressed
that hope repeatedly. “There’s a theory that,
in April, when it gets warm—historically,
that has been able to kill the virus,” Trump
said on 14 February. But what’s known about
other diseases doesn’t offer much support for
the idea that COVID-19 will suddenly disap-
pear over the next few weeks.
Different diseases have different patterns.Some peak in early or late winter, others in
spring, summer, or fall. Some diseases have
different seasonal peaks depending on lati-
tude. And many have no seasonal cycle at
all. So no one knows whether SARS-CoV-2,
the virus that causes COVID-19, will change
its behavior come spring. “I would caution
overinterpreting that hypothesis,” Nancy
Messonnier, the point person for COVID-
at the U.S. Centers for Disease Control and
Prevention, said at a press conference on
12 February. If the seasons do affect SARS-
CoV-2, it could nevertheless defy that pattern
in this first year and keep spreading, because
humanity has not had a chance to build im-
munity to it.
Even for well-known seasonal diseases,
it’s not clear why they wax and wane dur-
ing the calendar year. “It’s an absolute swine
of a field,” says Andrew Loudon, a chrono-
biologist at the University of Manchester.
Investigating a hypothesis over several sea-By Jon Cohen People seeking help for pandemic influenza in
Brazil in July 2009, when cold weather boosted the
spread of the disease.