They survived the coronavirus. Then they tested positive again. Why?
March 13, 2020
BEIJING —
The neighbors were
free at last.
After weeks of
confinement to their apartments because one person in the building had tested
positive for coronavirus,
they were throwing a party to celebrate his recovery and their release.
It was Feb. 24,
and Mr. Wang, a resident of Xuzhou, in Jiangsu province, appeared to have
emerged victorious from a monthlong battle with the illness. Sixty-five
residents of his building gathered downstairs to greet Wang with bouquets of
pink flowers, a cake with a flamingo on it, and a red banner that read: “With
strong neighborly feelings, we welcome you home.”
They pressed in
close around him for a group photo that was captured in a local news video.
Three days later,
though, Wang tested positive for the coronavirus again. He was re-hospitalized
and his neighbors were locked down once more. His current condition is unknown.
Wang, whose full
name has not been disclosed for privacy reasons, is one of more than 100
reported cases of Chinese patients who have been released from hospitals as
survivors of the new coronavirus — only to test positive for it a second time
in the bewildering math of this mysterious illness.
The science
surrounding these apparent reinfections is further complicated by China’s
handling of the outbreak, which since January has been marred by faulty
testing procedures and questionable case counting methods with shifting definitions. In
addition, the overburdened healthcare system has put pressure on doctors
to discharge people who may not have fully recovered to free up beds for newly
infected patients.
China has been
praised in recent weeks by the World Health Organization for containing the
virus. But the Communist Party’s early moves to suppress public knowledge on
the extent of infections prompt concerns over the accuracy of information about
recovered patients who retest positive but may have been misdiagnosed in the
first place.
Such cases account
for less than 0.2% of China’s total infections — not enough to cause alarm. But
they are raising questions in China about the reliability of diagnostic tests,
the possibility of reinfection and whether patients are wrongly designated as
“recovered” and released too early from hospitals.
Although most
patients who retest positive do not display clinical symptoms, some have
developed fevers and other signs of the virus. One such patient, a 36-year-old
man, died in Wuhan on March 2, five days after being declared
recovered.
His diagnosis,
according to hospital reports published in local media before they were
censored, was respiratory tract obstruction, respiratory failure and COVID-19,
the official name for the illness caused by the coronavirus.
China’s National
Health Commission says 64,216 out of 80,991 confirmed COVID-19 patients have
recovered, and 3,179 have died. There is no official record of how many
recovered patients have retested positive and returned to hospitals, but such
cases have been reported in the provinces of Hubei, Guangdong, Hainan, Sichuan
and Jiangsu, and the cities of Tianjin and Chongqing.
In Guangdong,
officials responsible for the coronavirus response announced Feb. 25 that 14% of declared recoveries in the
province had later retested positive.
The dynamic is
also playing out in other countries: Two such cases have emerged in Japan and South
Korea, though the Korean patient has been released from hospital after
retesting negative five times.
Scientists in and
outside China agree that reinfection is a highly unlikely explanation for the
patients who retest positive. They say testing errors are more likely to blame
— either false negatives that resulted in patients being discharged too early,
or false positives when they retested and were taken back into hospital.
Those errors could
be attributed to contaminated test samples, human error while taking swabs, or
an oversensitive nucleic acid test that detects strands of virus. When a person
gets sick with any kind of viral infection, their immune system naturally
develops antibodies that should protect them from contracting the illness again
after they’ve recovered.
Even in cases
where that immunity wears off, it shouldn’t be as quick as within a few days or
weeks, said Dr. Keiji Fukuda, director of Hong Kong University’s School
of Public Health.
“If you get an
infection, your immune system is revved up against that virus,” he said. “To
get reinfected again when you’re in that situation would be quite unusual
unless your immune system was not functioning right.”
What’s more likely
is that people are being released from hospitals while still carrying dormant
fragments of the disease that are not infectious but resemble the virus when
put through a nucleic acid test, he said.
“The test may be
positive, but the infection is not there,” he said.
Another
possibility is that the level of virus fell below the threshold that tests
could detect but then resurfaced, said Dr.
Clifford Lane, deputy director for Clinical Research and Special Projects
at the National Institute of Allergy and Infectious Diseases.
“So it looks like
they cleared the virus and then the virus came back,” Lane said. “But they
never really cleared it and they had a more prolonged course of infection.”
Lane was one of
only two U.S. experts in a World Health Organization delegation that visited
China in February. He said Chinese experts told the visitors that there were no
examples of people who became “reinfected.”
The best way to
prove reinfection, Lane said, would be to sequence the genomes of the initial
and subsequent viruses that circulated in a patient. If there is a difference
between the two, that would suggest that the virus had mutated enough to evade
the patient’s antibodies and prompt a second infection.
Developing a
vaccine would be significantly more difficult if the virus is changing fast
enough to cause true reinfections. It would undermine the immunity patients
develop from natural infections.
It’s too early to
know the true cause of these apparent reinfections, Lane said, especially
because cases are so rare.
“These are
exceptions,” he added. “These are not the rule.”
Another potential
explanation is that some patients may also have been discharged too early
because of pressure on hospitals to free up beds for new patients.
“If you don’t
discharge them, who’s going to save the other patients? You need to make
trade-offs,” one unnamed doctor said in a report
by the Paper, a Shanghai-based news outlet.
A doctor at a
Wuhan hospital told the Paper that he’d seen discharged patients still using
oxygen tanks, having trouble walking and displaying obvious clinical symptoms,
including serious lung infections, in February. Some of the recovered patients
had worse clinical symptoms than the new, mild cases entering the hospitals, he
said.
But the situation
improved in late February, when fewer patients turned up at Wuhan’s hospitals,
enabling them to keep patients longer.
Chinese
authorities claim that none of the patients who tested positive again have
infected others. If true, it’s an encouraging sign that even if some discharged
patients are still carrying low levels of the virus, they are not contagious.
But one study
by Chinese scientists published last month in the Journal of the American
Medical Assn. raised questions about testing. The study examined four medical
workers in Wuhan, all infected with coronavirus and then declared recovered
according to national criteria. But five to 13 days after the four were
released from quarantine, they all tested positive again. They were then each
given three repeat tests over the next four to five days. All were positive.
Dr. Dale Fisher, professor of medicine at the National
University of Singapore and another participant in the WHO’s China delegation,
said the apparent reappearance of coronavirus in recovered patients was
probably because of “excessive” testing and follow-up on discharged cases in
China.
“The outbreak is
being driven by people who are spreading it in those first five days while
they’re symptomatic and before they’re isolated ... when people are going
around coughing and undiagnosed, infecting people,” he said. “The things to
worry about are at the other end of the illness.”
Times staff
writer Victoria Kim in Seoul and Nicole Liu of The Times’ Beijing bureau
contributed to this report.
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