An enduring coronavirus mystery: Why do only some get sick?
S E E D E D C O N T E N T
Months into a pandemic that has caused more than 500,000 deaths worldwide, scientists are still trying to answer crucial questions about the coronavirus.
Chief among them: everything about asymptomatic patients.
People who contracted COVID-19 but didn't get sick and had no symptoms have been one of the most confounding factors of the public health emergency. The United States has more than 2.5 million confirmed coronavirus cases, but it's likely that many asymptomatic people have fallen through the cracks of official counts.
Now, scientists say that without a better understanding of how many people have been asymptomatically infected, it's difficult to know precisely how they contribute to the spread of the virus and whether they have developed antibodies or other protections that would confer some type of immunity against reinfection.
Dr. Jorge Mercado, a pulmonologist and critical care doctor at New York University's Langone Hospital-Brooklyn, said scientists still aren't sure why some people who have been exposed to the virus get very sick, while others develop no symptoms.
"We really don't know much about this disease," he said. "We know a little more than we did three months ago, but there are still a lot of things we don't have answers to."
Public health officials are struggling to get a handle on the true number of people who have been infected. The Centers for Disease Control and Prevention said Thursday that the number of COVID-19 cases in the U.S. — including those that are asymptomatic — may be 10 times higher than what has been reported, meaning the true case count could be closer to 23 million.
"Our best estimate right now is that for every case that's reported, there actually are 10 other infections," Dr. Robert Redfield, director of the CDC, said Thursday.
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Early on, many asymptomatic cases went unnoticed because states were dealing with dire shortages of test kits and supplies, which limited testing capacity to only the sickest patients. Many asymptomatic people likely had no idea they were ever positive, said Dr. Marybeth Sexton, an assistant professor of medicine at Emory University in Atlanta.
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"We tend to pick up asymptomatic or mildly symptomatic people when we do contact tracing, so when we get someone who is positive and we start testing people they've been in contact with," she said. "I think it'll be a long time before we know for sure what the true percentage is."
Sexton added that the virus' long incubation period has also led to some confusion over how "asymptomatic" is defined. According to the CDC, it could take up to 14 days after exposure for someone to show any symptoms.
"There are people who are positive but truly have no symptoms, and there are people who go on to develop very mild or atypical symptoms, and then there are people who think they are asymptomatic until you query them about some of the more unusual manifestations of COVID-19," she said. "But sometimes, these all get lumped together as 'asymptomatic.'"
It's thought that people in all three categories — including those who are presymptomatic — can transmit the virus, although there was again some confusion about the nature of asymptomatic spread. In early June, the World Health Organization was forced to clarify that the coronavirus can be spread by people with no symptoms after one of the agency's top infectious disease epidemiologists, Maria Van Kerkhove, said she thought asymptomatic spread of COVID-19 was "very rare."
Van Kerkhove's assessment was roundly criticized by scientists around the world. A day later, she said her response had been based on several studies that hadn't undergone peer review, and she made it clear that the WHO's guidance still stands.
Yet even if scientists are sure that asymptomatic people can be so-called silent spreaders — transmitting COVID-19 even if they show no symptoms — it's not known to what degree they are contributing to the outbreaks.
"It's been very hard thus far to nail down how much of transmission is due to asymptomatic people and how much is due to people who get quite sick," Sexton said.
Another big unknown is how asymptomatic people's immune systems respond and whether they will develop antibodies or other protections against the virus.
A study published June 18 in the journal Nature Medicine was the first to examine the immune responses in asymptomatic coronavirus patients. The researchers followed 37 asymptomatic people in China's Wanzhou district and compared them to 37 people who had symptoms.
Although it was a small study, the scientists found that the asymptomatic patients did develop antibodies, which are protective proteins the immune system produces in response to infections. But the researchers discovered that antibody levels among those people diminished within two to three months.
It's not yet known whether COVID-19 antibodies confer any kind of immunity, but if they do, the recent results suggest that the protections may not last long — particularly among those who are asymptomatic.
Mercado said it's possible that even low antibody levels could afford some protection, although more studies are needed to know for sure.
"There's a glimmer of hope that an antibody response can at least decrease the chances that you'll progress to a severe disease," he said.
Dr. Daniel Kuritzkes, chief of the infectious diseases division at Brigham and Women's Hospital in Boston, said it's not altogether surprising that asymptomatic patients would have more modest immune responses. But he noted an intriguing finding from the Nature Medicine study that further muddies the definition of "asymptomatic" coronavirus patients.
In CT scans of the study participants, the researchers found signs of lung inflammation, known as pulmonary infiltrates, even in people who showed no symptoms. Signatures of inflammation were observed in 57 percent of the asymptomatic group, a "surprising" find because it's not common to conduct CT scans on people who aren't exhibiting symptoms of a respiratory infection, Kuritzkes said.
"It makes you wonder if they really were asymptomatic, because clearly they had some pneumonia," he said. "It just goes to show that the absence of symptoms is not the absence of infection."
Sexton said that the recent study, while small, reveals some insights into the immune responses of asymptomatic patients but that the results also show how much remains unknown about this population.
"Until we know how much transmission asymptomatic people are responsible for, it makes an incredible amount of sense to keep stressing that everyone should wear a mask," she said. "If you happen to be in that category and you're wearing a mask, that's going to keep you from infecting people and putting those viral particles out in the environment. And everyone else wearing a mask is doing the same for you."
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Yet it was so easy to jump on China for not immediately understanding what they were dealing with, and the delays caused by that. But the delays in China did not compare with the delays and mismanagement of the American government. The numbers tell that story.
In the movie Sully, the Air Transport Board tried to pin negligence on Sully for not IMMEDIATELY making a turn to return to La Guardia or go to Teterborough Airport when both engines were stopped by birds, but as Sully explained, people are not computers or robots, and one has to take into consideration the human factor when speaking of reaction to something totally unexpected.
Sully at no time had any option to reach the airport...he simply didn't have enough altitude. His experience with gliders and sailplanes gave him the skills to land on the water.
The Chinese delayed informing other countries about the potential of a pandemic and mismanaged their response from the very start. Conflicting information from so called experts to Trump slowed down the response of the US as to the severity and spread of the virus. Looks like your adopted country is still having a lot of problems with the outbreak. Can we really trust the numbers they put out?
I never said China did NOT delay, and since I've explained why I think China's numbers are logical a few times on this site already I'm not going to waste my time bothering to explain it yet again to someone whose attitude is such that it would be useless to do so anyway.
By the way, since you are so knowledgeable about the movie Sully, why don't you try to answer the Movie quiz?
I have flown in a glider myself, and the trick for landing in the water was to maintain the nose with enough elevation so it would not dig into the water which at speed would most likely flip the plane.
It’s crazy to me how little we know about something that’s spread as far and wide as COVID-19. I mean, I get that studies take time. They also depend on financial support and volunteers.
I just spoke to someone I hadn’t talked to in a long time. She had COV-19 and symptoms lasted 30 days! Some were unconventional and some were “expected” based on current knowledge. She didn’t get the lung issues that’s putting people in the hospital, but she said it was absolutely brutal. She works in a sleep/respiratory specialists office... well, she’s been furloughed now. She was furloughed soon after she became ill.
My uncle had typical symptoms and he was very ill for about two weeks, but didn’t need hospitalization. My aunt had very few symptoms for a few days. And my cousin was somewhere between. They all live in the same house. My uncle is retired. My aunt works in a hospital in an office. My cousin works in a medical lab. My uncle was the first to fall ill though. My aunt followed by a day or two and my cousin a day or two after my aunt. It’s a messed up thing, this COVID.
Actually the reason why different people who get infected have different reactions was never a mystery to me. Simply stated-- its because some people's immun systems are stronger than others.
When I first heard about the virus (IIRC it was sometime in Februrary), of clurse I "social distanced", wors a mask" and wahsed my hands frequently. ButI realized my main focus should be to build up my innune system. (Something I already knew about, but wanted to learn more). So I spent hours researching it.
And I investigated both the Western approach as well as that of TCM ("traditional Chinese Medicine").
Chinese Medicine is very big on Mushrooms to enhance immunity--- some more than others. So I found what seemed like the best formula. I also started going back to accupuncture-- specifically to built up my immune system. (As the virus spread, unfortunautely they had to close down.
Western medic89ne is mainly focused on curing conditions after they appear rather than prevention. So I turned to "Alternative medicine".
Recent discoveries indicate that a major source of Immunity comes from the bacteria in your intestines! So I changed my brand of that , etc) to a better brand and increased the dose.. I also investigated other things-- some "glandulars", herbs, etc.
Also your health has a lot to do with the state opf your consciousness-- a subject on which I know much-- so I practiced what I knew.
So my focus was on stregthening my Immune system.
How'd it work out?
Well, not surprisingly I got the Virus. IIRC it was in early March? The worst part lasted over a week-- in all it was almost two weeks 'till I was totally free on it. At its worst it wasn't too bad-- quite similar to other incidences in the past of getting the flu. Some aches and pains. Wanting sleep most of any 24 hours period. More coughing than the regular flu. Not all that bad an experience.
Forget too mention-- I do Reiki, a form pf energy healing. Did it on myself for long periods every day. That, all the sleep, and nutritional approaches and working with consciousness made it not much of an ordeal.
P.S; because of my focus on healthy practices (not being overweight, npot being a alcoholic, eating super-healthy, meditating, etc I have gotten the regular flu for many, many years-- and I don't get glu shots).
Chinese doctors are recommending using a mix of traditional and modern medicines to treat the virus.