C***S
发帖数: 1159 | 1 要点：罐装病毒导致的感冒占比是10%到30%。这次的不同之处是能攻击下呼吸道。R0在
2左右，感染能力一般。
这次宣传出了大问题，应该一开始就说新型流感，重症可以转化为肺炎。现在直接封城
，简单粗暴，是上了港灿和老酱的当。
Science News
How the new coronavirus stacks up against SARS and MERS
For the third time since around 2003, a coronavirus has jumped from animals
to people
2019-nCoV transmission electron micrograph
A new coronavirus called 2019 novel coronavirus, or 2019-nCoV, (seen here in
a transmission electron micrograph) is spreading in China. It is similar to
both SARS and MERS.
COURTESY: IVDC, CHINA CDC VIA GISAID
By Tina Hesman Saey
JANUARY 24, 2020 AT 4:22 PM
Coronaviruses, one of a variety of viruses that cause colds, have been
making people cough and sneeze seemingly forever. But occasionally, a new
version infects people and causes serious illness and deaths.
That is happening now with the coronavirus that has killed at least 26
people and sickened at least 900 since it emerged in central China in
December. The World Health Organization is monitoring the virus’s spread to
see whether it will turn into a global public health emergency (SN: 1/23/20
).
Among the ill are two people in the United States who contracted the virus
during travels in China. A Chicago woman in her 60s is the second U.S. case
of the new coronavirus, the Centers for Disease Control and Prevention
confirmed January 24 in a news conference.
Officials are currently monitoring 63 people across 22 states for signs of
the pneumonia-like disease, including fever, cough and other respiratory
symptoms. Of those people, 11 have tested negative for the virus. Two,
including the newest case and another patient in Seattle, tested positive,
the CDC reported (SN: 1/21/20).
France reported two cases on January 24 as well, the first in Europe.
Much still remains unknown about the new coronavirus (SN: 1/10/20), which
for now is being called 2019 novel coronavirus, or 2019-nCoV. Lessons
learned from previous coronavirus outbreaks, including severe acute
respiratory syndrome, or SARS, and Middle East respiratory syndrome, or MERS
, may help health officials head off some of the more serious consequences
from this virus outbreak.
What are coronaviruses?
Coronaviruses are round and surrounded by a halo of spiky proteins, giving
them a resemblance to a crown or the sun’s wispy corona.
Four major categories, or genera, of coronavirus exist. They’re known by
the Greek letters alpha, beta, delta and gamma. Only alpha and beta
coronaviruses are known to infect people. These viruses spread through the
air, and just four types (known as 229E, NL63, OC43 and HKU1) are
responsible for about 10 to 30 percent of colds around the world.
What makes a virus a coronavirus is only loosely enshrined in its DNA. “The
coronavirus designation is less about the genetics and more about the way
it appears under a microscope,” says Brent C. Satterfield, cofounder and
chief scientific officer of Co-Diagnostics, a company based in Salt Lake
City and Gujarat, India, that is developing molecular tests for diagnosing
coronavirus infections.
Coronaviruses’ genetic makeup is composed of RNA, a single-stranded
chemical cousin of DNA. Viruses in the family often aren’t very similar on
the genetic level, with some types having more differences between them than
humans have from elephants, Satterfield says.
The new virus’s proteins are between 70 and 99 percent identical to their
counterparts in the SARS virus, says Karla Satchell, a microbiologist and
immunologist at Northwestern University Feinberg School of Medicine in
Chicago.
similar amino acids in coronavirus protein
A new coronavirus spreading in China is similar to SARS, but many of its
proteins have important differences. Here, the new virus’s similarities (
gray) and differences (red) with SARS of the amino acids in a protein that
studs the surface of the viruses are shown in two views. Those differences
may affect the viruses’ infectivity and how well drugs developed to combat
other coronaviruses work against the new one.
COURTESY OF GISAID INITIATIVE
How dangerous is a coronavirus infection?
Usually coronavirus illnesses are fairly mild, affecting just the upper
airway. But the new virus, as well as both SARS and MERS, are different.
Those three types of betacoronaviruses can latch onto proteins studding the
outside of lung cells, and penetrate much deeper into the airway than cold-
causing coronaviruses, says Anthony Fauci, director of the U.S. National
Institute of Allergy and Infectious Diseases in Bethesda, M.D. The 2019
version is “a disease that causes more lung disease than sniffles,” Fauci
says.
Damage to the lungs can make the viruses deadly. In 2003 and 2004, SARS
killed nearly 10 percent of the 8,096 people in 29 countries who fell ill. A
total of 774 people died, according to the World Health Organization.
MERS is even more deadly, claiming about 30 percent of people it infects.
Unlike SARS, outbreaks of that virus are still simmering, Fauci says. Since
2012, MERS has caused 2,494 confirmed cases in 27 countries and killed 858
people.
MERS can spread from person to person, and some “superspreaders” have
passed the virus on to many others. Most famously, 186 people contracted
MERS after one businessman unwittingly brought the virus to South Korea in
2015 and spread it to others. Another superspreader who caught MERS from
that man passed the virus to 82 people over just two days while being
treated in a hospital emergency room (SN: 7/8/16).
Right now, 2019-nCoV appears to be less virulent, with about a 4 percent
mortality rate. But that number is still a moving target as more cases are
diagnosed, Fauci says. As of January 23, the new coronavirus had infected
more than 581 people, with about a quarter of those becoming seriously ill,
according to the WHO. By January 24, the number of reported infections had
risen to at least 900.
An analysis of the illness in the first 41 patients diagnosed with 2019-nCoV
from Wuhan, China suggests that the virus acts similarly to SARS and MERS.
Like the other two, 2019-nCoV causes pneumonia. But unlike those viruses,
the new one rarely produces runny noses or intestinal symptoms, researchers
report January 24 in the Lancet. Most of the people affected in that first
group were healthy, with fewer than a third having chronic medical
conditions that could make them more vulnerable to infection.
Disease tracker
An infection with a new coronavirus begins with an onset of symptoms
including fever, cough and fatigue. Those symptoms can then intensify fairly
quickly, resulting in hospital admission and acute respiratory disease
syndrome, or ARDS (median time from onset of symptoms, shown).
How fast a new coronavirus can sicken
coronavirus infection timeline
C. HUANG ET AL/LANCET 2020
Where do new coronaviruses come from?
Coronaviruses are zoonotic, meaning they originate in animals and sometimes
leap to humans. The first 2019-nCoV infections detected in December were in
patients who had visited the Huanan seafood market in Wuhan. The market was
closed January 1, but health officials have yet to determine from which type
of animal the virus jumped to humans.
Bats are often thought of as a source of coronaviruses, but in most cases
they don’t pass the virus directly on to humans. SARS probably first jumped
from bats into raccoon dogs or palm civets before making the leap to humans
. All the pieces necessary to re-create SARS are circulating among bats,
though that virus has not been seen since 2004 (SN: 11/30/17).
MERS, meanwhile, went from bats to camels before leaping to humans (SN: 2/25
/14). A paper published January 22 in the Journal of Medical Virology
suggests that the new coronavirus has components from bat coronaviruses, but
that snakes may have passed the virus to humans. But many virologists are
skeptical that snakes are behind the outbreak (SN: 1/24/20).
How contagious are coronaviruses?
It depends on the coronavirus, but neither SARS or MERS have been able to
sustain human-to-human transmission the way influenza viruses can, Fauci
says. That’s because the viruses haven’t fully adapted to infect humans,
“and maybe they never will,” he says.
Still, “this is a family of viruses that was formerly just the common cold,
” he says. “But now, in the last 18 years, we’ve had three examples of it
jumping species and causing serious disease in humans.” He and colleagues
wrote an article published January 23 in JAMA to illustrate what they see as
the growing threat from coronaviruses.
In Wuhan, the new coronavirus has been able to transmit down a chain of up
to four people, health officials said. Five members of a family from
Shenzhen, China caught the virus when they visited infected relatives in
Wuhan, researchers report January 24 in the Lancet. Travelers have also
carried the virus from China to at least seven other countries, including
the United States. No human-to-human transmission has yet been reported
outside of China, the WHO said. All of the deaths have also been in that
country.
Epidemiologists are frantically calculating how infectious the new virus is,
says Maimuna Majumder, a computational epidemiologist at Boston Children’s
Hospital and Harvard Medical School.
The number that describes how many people a newly infected person is likely
to pass a virus to is called R0, pronounced R naught (SN: 5/28/19). SARS,
for instance, had an R0 between two and five, meaning that in a fully
susceptible population an infected person could potentially spread the virus
to two to five others. (Highly contagious measles, in comparison, has a R0
from 12 to 18.)
Estimates for the infectivity of the new virus range from the WHO’s
estimate of 1.4 to 2.5 to a much bigger 3.6 to 4.0 calculation from Jonathan
Read of Lancaster University in England and colleagues. Read’s group
estimates that only about 5.1 percent of cases in Wuhan have been identified
. The researchers reported the preliminary results January 24 at medRxiv.org.
That’s probably not because the Chinese government is covering up how bad
the outbreak is, Majumder says. Many people may have had only mild symptoms
or none at all. Those people probably wouldn’t go to the doctor and get
tested for the virus.
Majumder and Harvard colleague Kenneth Mandl used a different method to
calculate R0 for the new virus, estimating based on cases reported as of
January 22 that its transmissibility falls from 2.0 to 3.3. Their results
were posted to SSRN on January 23.
Meanwhile, Christian Althaus and Julien Riou, both of the University of Bern
in Switzerland, posted data to Github supporting their calculation that the
new virus’s infectivity is between 1.4 and 3.8. Each of those calculations
was arrived at using different methods. While they are slightly different,
they overlap, and Majumder says she’s reassured that the numbers are
similar.
Similar infectivity to SARS doesn’t mean the new virus will spread like
that one did.
“Having SARS in [our] history can help inform some these decisions that we
’re going to make now. Back then, we were less prepared than we are now,”
Majumder says.
What treatments are available?
For now, all doctors can do is treat symptoms of the new disease.
Researchers have also developed some experimental treatments based on SARS
and MERS, including antibodies that may help combat the infections, Fauci
says.
Getting samples of the new virus may allow researchers to develop “
monoclonal” antibodies in the lab. Or scientists may be able to take immune
B cells from people who already have recovered from the virus to produce
antibodies to help other infected people.
Some antiviral medications have shown promise in treating MERS, and are
being tested for their effectiveness against 2019-nCoV. Experimental
vaccines, Facui wrote in JAMA, including some based on RNA, are also in the
works.
Erin Garcia de Jesus contributed to reporting of this story.
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