22 3.29.20 Illustration by Ori Toor
Studies Show By Kim Tingley
As public health offi cials struggle to
contain the spread of the coronavirus,
determining whether a person has a fever
is now a high-stakes matter, and using
temperature guns to screen people has
become a visible strategy for detecting
possible cases. ‘‘Any infectious disease —
one of the cardinal signs of infection is
raised body temperature,’’ says Waleed
Javaid, the director of infection preven-
tion and control for the Mount Sinai
Downtown Network. But there’s a catch:
‘‘That means you know the body tempera-
ture before you raised it.’’
Body temperature varies considerably
both among and within people, based
on weight, height, physical activity, the
weather, clothing. Older people tend to
be cooler than younger people. A recent
review suggests women might tend to
be slightly warmer than men. Tempera-
ture also fl uctuates with the sleep-wake
cycle. Of course, public health offi cials
can’t know each person’s usual thermal
patterns, so their advice is based on pop-
ulation averages. Yet those numbers aren’t
consistent, either, and most refer to oral
temperature, which is considered more
accurate than an infrared scan of the fore-
head. The Centers for Disease Control and
Prevention considers above 100 to be a
fl u-related fever. The National Institutes
of Health says an adult with a temperature
above 99 ‘‘probably’’ has a fever, depend-
ing on the time of day. Before the current
pandemic, hospitals would generally
assess fever and act upon it diff erently in
response to individual patients and diag-
noses; schools have had various thresholds
to determine when parents should keep
their children home. Perhaps the most
well-known benchmark is 98.6 degrees,
which many people, including physicians
and public health agencies, consider to
be a baseline. ‘‘All of us think back to our
mothers taking our temperature and say-
ing: ‘It’s 98.6. You’re going to school,’ ’’ says
Dr. Julie Parsonnet, an infectious-diseases
specialist at Stanford University.
That number dates to 1851, when a
German physician named Carl Reinhold
August Wunderlich began taking what he
purported were millions of temperature
readings from 25,000 patients in Leipzig.
Their average, he announced, was the
Celsius equivalent of 98.6. That fi gure,
which he defi ned as ‘‘normal,’’ has persist-
ed, despite numerous more recent stud-
ies that put the average closer to 97.88 orHumans seem to have cooled over
the past 150 years. What does that
say about the relationship between
body temperature and health?