Covid-19 is mysteriously sparing kids and killing the elderly.
Understanding why may help defeat the virus.
One of the few mercies of the spreading COVID-19 is
that it leaves young children virtually untouched — a mystery virologists
say may hold vital clues as to how the virus works.
In China, only 2.4 percent of reported cases were children
and only 0.2 percent of reported cases were children who got critically
ill, according to the World
Health Organization. China has reported no case of a young child dying
of the disease covid-19.
Meanwhile, the
COVID-19
has proved especially
deadly on the other end of the age spectrum. The
fatality rate in China for those over 80 is an
estimated 21.9 percent, per
the WHO. ( here it
is 14.8%). For ages 10 to 39, however, the
fatality rate is roughly 0.2 percent, according to a separate study drawing
on patient records of 44,672 confirmed cases. And fatalities and severe
symptoms are almost nonexistent at even younger ages.
That means the
COVID-19 is behaving very differently from other
viruses, like seasonal influenza,
which are usually especially dangerous for the very young and very old.
“With respiratory infections like this, we usually see a
U-shaped curve on who gets hits hardest. Young children at one end of the U
because their immune systems aren’t yet developed and old people at the other
end because their immune systems grow weaker,” said Vineet Menachery, a
virologist at the University of Texas Medical Branch. “With this virus, one
side of the U is just completely missing.”
Figuring out why children are so unaffected could lead to
breakthroughs in understanding how and why the virus sickens and kills other
age groups, said Frank Esper, a pediatric infectious disease specialist at
Cleveland Clinic Children’s. Among the questions Esper and others are
exploring: Is the severity of infection related to what patients were exposed
to previously? Does it have to do with how our immune systems change with age?
Or could it be due to pollution damage in the lungs that people accumulate
over years?
“Or maybe it has nothing to do with the virus and has to do
with host, like underlying conditions in the lungs, diabetes or hypertension.
After all, few 7-year-olds or newborns have hypertension,” said Esper, who
studies viral respiratory infections and new diseases. “Figuring out what’s at
play here could be helpful in so many ways."
Previous coronavirus outbreaks have also mysteriously spared
the young. No children died during
the SARS outbreak in 2002, which killed 774 people. And
few children developed symptoms from the
deadly MERS coronavirus, which has killed
858 since 2012.
MICE RESEARCH
To find out why, Menachery has been giving mice at his Texas
lab SARS — which is a very close cousin to
the
COVID-19. Baby
mice at his lab have shaken off the
infection, while the older mice have had
their lungs and bodies ravaged by the
disease.
Menachery found the older mice’s fatalities were strongly
related to not just weakness in their immune systems but also a
“disregulation” that caused their immune systems to
overreact to the SARS coronavirus. That’s similar to how
humans die of infections from the
COVID-19, called
SARS-CoV-2.
“It’s the aggressive response from their immune system that is
damaging them, even more than the infection itself,” Menachery said. “It’s
like police responding to a misdemeanor with a SWAT team crashing through the
door.”
The question he and others have still struggled to answer,
however, is why the baby mice escape unscathed.
CHILD SURVIVAL THEORIES
Some experts have floated a theory that because children are so
heavily exposed to four other "Common" coronaviruses,
which circulate every year and cause the common
cold, that may give kids some kind of strengthened immunity. But many have
doubts about that argument because adults catch the
common cold coronaviruses too, and the immune systems of children —
especially under the age of five — are underdeveloped, which should make them
more vulnerable, not less.
“If it bears out that kids are less prone to infection, then I
suspect there’s something more mechanical than immunological going on,” said
Esper, the pediatric infection expert. “Something about the receptors in
children’s bodies or their lungs is interfering with the virus’ ability to
attach itself.”
“It just shows you how much we don’t know about this virus,”
said Stuart Weston, a virologist at the University of Maryland School of
Medicine who has been testing anti-viral drugs that could help treat the new
coronavirus. “The focus now is on vaccines and treatment, but there are all
these big questions we’re going to want to answer in the long-term if we want
to really understand how these coronaviruses work.”
WHY CLOSE SCHOOLS ?
So given all that, does it make sense to close
schools?
Because so few cases have been found in children, there’s been
speculation children are simply less likely to get infected.
But many epidemiologists suspect mild symptoms may simply be
masking that children are getting infected the same rates as adults. New data
published last week by Chinese researchers showed authorities searching for
coronavirus cases based on symptoms found lower rates in kids. But when they
relied on contact tracing — testing people who come in contact with a
confirmed case — children seemed to be getting
infected at the same rate as adults.
“We know from pandemic research that closing schools can be
effective in slowing down transmission because children are often a driver of
infection. They spread it to parents, relatives and the wider community,” said
Caitlin Rivers, an epidemiologist at the Johns Hopkins Center for Health
Security.
Some districts may find themselves closing schools because it
will be tough to stay open as teachers, principals and janitors get infected,
said Rivers, who has children herself. “We may end up closing schools in part
to protect the adults and staff."
SOURCE Washington Post
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