What The Data Say About Asymptomatic Covid Infections
Roughly one in five people with COVID-19 dont experience symptoms.Credit: Ezra Acayan/Getty
How many people dont experience any symptoms after becoming infected with SARS-CoV-2? And what is their role in spreading COVID-19? These have been key questions since the beginning of the pandemic.
Now, evidence suggests that about one in five infected people will experience no symptoms, and they will transmit the virus to significantly fewer people than someone with symptoms. But researchers are divided about whether asymptomatic infections are acting as a silent driver of the pandemic.
Although there is a growing understanding of asymptomatic infections, researchers say that people should continue to use measures to reduce viral spread, including social distancing and wearing masks, regardless of whether they have symptoms.
The issue with putting a reliable figure on the rate of asymptomatic COVID-19 is distinguishing between people who are asymptomatic and pre-symptomatic, says Krutika Kuppalli, an infectious-disease researcher at the Medical University of South Carolina in Charleston. Asymptomatic is someone who never developed symptoms ever throughout the course of their disease, and pre-symptomatic is somebody who has mild symptoms before they do go on to develop symptoms, Kuppalli says. There is also no standardized accepted definition of that, she says.
What To Do If You Have Covid
People with COVID-19 should seek advice from their local health authorities on what actions to take and follow the appropriate guidelines.
Anyone with COVID-19 should advise the people they have been in contact with that they have tested positive, so they can also get a test.
The only time a person with COVID-19 should leave their home is to seek medical care if their doctor has advised them to do so.
Asymptomatic Covid Patients Are Responsible For Nearly Half Of All Transmitted Cases
A lack of symptoms doesn’t mean you aren’t able to spread the virus, either. According to the study, asymptomatic cases and pre-symptomatic cases “substantially drive community transmission.”
“We can tell that more that 50 percent of the transmission happening in the community is from people without symptomsthose who are asymptomatic and pre-symptomatic,” senior author Mercedes Pascual, PhD, the Louis Block Professor of Ecology and Evolution at the University of Chicago, said in a statement. And for more up-to-date COVID news delivered right to your inbox, .
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Similar Viral Loads Found In South Korea
Kim and colleagues found almost the same proportion, 19% of 213 patients, without severe symptoms of COVID-19 remained asymptomatic through potential exposure, lab confirmation, and hospital admission.
The upper respiratory tract viral load did not differ significantly between asymptomatic and symptomatic individuals in upper respiratory tract samples in South Korea.
“Our data adds to the recent growing body of evidence that asymptomatic individuals with SARS-CoV-2 infection are indeed contributing to the ongoing community spread of COVID-19, senior study author Kim told Medscape Medical News.
The mean cycle threshold values of SARS-CoV-2 genes, which reflect the viral load, “were highly similar between asymptomatic individuals and symptomatic patients,” added Kim, professor of infectious diseases and chief of the Office of Infection Control at Asan Medical Center in Seoul, South Korea.
The findings suggest that asymptomatic individuals have “a comparable potential for spreading the virus as much as symptomatic patients,” he said. “To prevent the transmission from asymptomatic individuals with SARS-CoV-2 infection, the use of face masks by the general public regardless of the presence of symptoms is highly recommended.”
“We were able to assess many asymptomatic individuals who were otherwise unlikely to be identified as cases of COVID-19,” the investigators note.
Continue To Rely On Tried
For people who think they may be experiencing symptoms but need to leave the house, the safest way to move about society requires wearing a high-quality mask around others, Salinas says, and isolating to the extent that you can. At this stage in the pandemic, Americans desperately need universal paid sick leave and free and easily accessible testing until that happens, individuals will unfairly remain responsible for interpreting their symptoms as best they can.
Unless youre able to regularly test, take note of how youre feeling every day and continue to mask up in public settings. If you feel healthy without pain relievers and cold medicines, considering your own circumstances and history, you can safely assume youre without symptoms, experts say. Anything less than your best means you should take every sniffle, ache, or cough seriously.
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Stop Wasting Covid Tests People
With the surge in cases, tests should be reserved for those who need them most.
Move over mimosas, because America has a fresh New Years tradition: struggling to get tested for COVID before returning to school or work. The line for brunch was replaced, last weekend, with line after line after line of weary citizens waiting to receive their viral clearance. Testing backlogs are only going to get worse from here, as case numbers continue their ascent. But amid the complaints about a lack of rapid-testing kits and long delays for lab results, Im reminded of the adage You are not stuck in traffic. You are traffic. Yes, the system failed us: Inadequate public investment in the nations testing infrastructure has worsened the congestion. But we can help ease it tooand clear the way for those who have the greatest need for their resultsby staying off the road whenever possible.
Its possible to feel outrage at this state of affairs while behaving as responsibly as possible, given the circumstances. This is the testing version of vaccine equity: the effort to ensure that life-saving inoculations dont disproportionately benefit the healthiest and wealthiest people. When the same principle is applied to diagnostics, it means that people at the lowest risk from COVID shouldnt buy up large stocks of at-home tests, or grab PCR appointments when theyre not experiencing symptoms.
Do Asymptomatic People Still Develop Covid Antibodies
Heres the good news: If you produce an asymptomatic COVID response, you will still get antibodiesbut they likely wont be as strong as someone who has a more severe response. It appears that everybody develops some antibodies, some better than others, Dr. Taege says. Theres discussion about whether or not this has to do with whether youre more symptomatic or less, and yes, the levels of antibodies is different, but the amount is always enough to interact with and control the virus.
Dr. Mir adds that immunity is more complex than having antibodies, and as with most things COVID-related, more research is needed. Immunity involves more than antibodies, so some patients may not have detectable antibodies but still be protected, explains Mir. All great questions, but we need more research and more time to answer them.
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You Can Still Have Lingering Issues From Covid Following An Asymptomatic Case
An asymptomatic case could also still affect you long-term. In fact, several studies have shown that long-term health issues arise in those who had COVID but had no symptoms. Eric J. Topol, MD, founder and director of Scripps Research Translational Institute, told TheWall Street Journal that at least four studies so far have analyzed the lung scans of asymptomatic individuals, finding that “half have significant abnormalities consistent with COVID pneumonia but without symptoms.” And a July study published in JAMA Cardiologydiscovered abnormal cardiac MRIs in both symptomatic and asymptomatic COVID patients, concluding that heart damage due to the virus is possible no matter how mild or severe your case is.
“There is a risk of internal hits to these people that they are unaware of,” Topol said. “When things happen slowly in a person, below the surface, you can end up with a chronic situation.” And for more on how the virus can progress, If You’ve Done This, You’re Twice as Likely to Develop Severe COVID.
Is It Common For Viruses To Affect People Of Varying Ages Differently
Age also seems to affect the degree to which people are asymptomatic when they contract a virus. The Duke study of children with COVID-19 found that asymptomatic cases were highest among kids ages 6 to 13. Asymptomatic cases were less common but still occurred 25% of the time in children ages 0 to 5 and teens who were 14 to 20 years old. The study did not look at adults, but older people have fared worse when they get COVID-19.
Beckham said its quite common for different viruses to affect people of various ages in different ways. Some can be more severe in children or young adults. Other infectious illnesses like SARS-CoV-2 and the flu are more dangerous to older people. People with underlying health conditions and older people have been among those who have been most critically ill and who have died at higher rates from COVID-19.
Kids seem to have lower overall rates of infection, but they clearly can get infected and they can be asymptomatic, Beckham said. Theres still a lot of work to be done to understand the epidemiology of these younger kids. I dont think we know exactly what role they play in the spread of the virus.
While researchers have much more to learn about how common asymptomatic cases of COVID-19 are and exactly how asymptomatic spread occurs, theres plenty of evidence to warrant concern and careful behavior now.
Beckhams take-home message to reduce asymptomatic spread boils down to this simple advice. Wear your mask.
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Heart Inflammation And Blood Clots
Just as imaging scans have revealed damage to the lungs of asymptomatic individuals, chest scans have also shown abnormalities in the hearts and blood of people with asymptomatic infectionsincluding blood clots and inflammation.
Thrombosis Journal and other publications have described severalcases of blood clots in the kidneys, lungs, and brains of people who hadnt had any symptoms. When these gel-like clumps get stuck in a vein, they prevent an organ from getting the blood it needs to functionwhich can lead to seizures, strokes, heart attacks, and death.
There have been relatively few of these case reportsand its unclear whether some patients might have had other underlying issues that could have caused a clot. But the Washington State researchers who reported on one case of renal blood clot write that it suggests that unexplained thrombus in otherwise asymptomatic patients can be a direct result of COVID-19 infection, and serves as a call to action for emergency department clinicians to treat unexplained thrombotic events as evidence of COVID-19.
Meanwhile, studies also suggest that asymptomatic infections could be causing harm to the heart. In May, cardiac MRI scans of 1,600 college athletes who had tested positive for COVID-19 revealed evidence of myocarditis, or inflammation of the heart muscle, in 37 people28 of whom hadnt had any symptoms, says Saurabh Rajpal, a cardiovascular disease specialist at the Ohio State University and lead author on the study.
Younger Patients More Likely To Be Asymptomatic
The meta-analysis also found those under the age of 39 were most likely to be asymptomatic, confirming previous research.
This indicated that young adults who often presented mild or no symptoms were a potential source of transmission in the community, study authors write.
The study is the biggest and most updated of its kind, covering Europe, the U.S., Africa, Asia, and South America. It included 19,884 people with a confirmed COVID-19 infection, with 11,069 being asymptomatic.
Our results could raise awareness among the public and policy makers and provide evidence for prevention strategies, Prof. Liu says.
Screening for asymptomatic infection is required, especially for countries and regions that have successfully controlled SARS-CoV-2. Asymptomatic infections should be under management similar to that for confirmed infections, including isolating and contact tracing.
South West News Service writer Mark Waghorn contributed to this report.
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If You Need Meds To Manage Your Symptoms You Have Symptoms
Congestion that youre treating with DayQuil or a headache that necessitates taking pain relievers is a red flag youre experiencing a symptom, Goldman says. Not only are you feeling less than your best, youre also hiding that crucial information from your family, co-workers, roommates and yourself.
If youre masking the symptoms, youre more likely to go to work, youre more likely to do things that will spread the disease, he says. Taking Tylenol, doing something to deal with the symptoms is certainly not going to hurt you. It may just be that you go outside and you arent aware youre sick and spread it to someone else. He recommends getting tested to confirm and doing everything you can to avoid others while you feel sick.
Covid: Us Halves Isolation Time For Asymptomatic Infection
US health officials have halved the recommended isolation time for people with asymptomatic Covid-19 from 10 to five days, amid a surge in cases.
The measure is expected to alleviate disruption caused by staff shortages in many areas because of infections.
The Centers for Disease Control says most transmissions happen in the two days before and three days after symptoms develop.
But experts have criticised the lack of testing requirements to end isolation.
The sharp rise in cases has been fuelled by the Omicron variant of the virus, which is now dominant in the US. Early studies suggest Omicron is more contagious than other variants, although milder.
The growing number of people having to isolate has put pressure on several industries, including air travel, with thousands of flights cancelled during the Christmas holiday.
Leaders of major US airlines were among those calling for the change, as cancellations continued for a fourth day on Tuesday.
The CDC said the new guidance was “motivated by science”, and that the isolation must be followed by five days of wearing a mask around others. The announcement came as more than 200,000 daily infections were confirmed in the past two days nationwide.
CDC director Dr Rochelle Walensky said the recommendation “balances what we know about the spread of the virus and the protection provided by vaccination and booster doses”.
“These updates ensure people can safely continue their daily lives,”Dr Walensky said in a statement.
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Wearing Masks Helps Prevent Asymptomatic Spread Of Covid
That means its all the more critical for people to follow public health measures that clearly work, chief among them wearing masks, staying far apart from people and washing hands frequently.
The closer we can get to 100% mask wearing, the quicker we can end this outbreak and get out of the current spike of the disease, Beckham said.
Public health experts estimate that about 60-to-70% of people in the U.S. routinely are wearing masks when theyre out in public and are exposed to people outside of their homes. Boosting mask wearing to 80-to-85% would dramatically drive down infections and result in fewer illnesses and deaths from COVID-19.
We need to remember to protect each other. Everybody has a grandparent or knows someone who is high-risk. Simply wearing a mask and maintaining six feet of distance from others works to reduce infections since we know that asymptomatic spread occurs, Beckham said.
In general, masks protect other people. But, new research also shows that people who wear masks may not get as sick if they get exposed to people with COVID-19. The mask may reduce the viral load that the person wearing it receives.
Wearing masks clearly works as do other prevention measures, Beckham said.
We all can significantly impact how much transmission is going on in the community. We all can protect grandparents and family members who may be at risk for severe disease.
People With Omicron Much More Likely To Be Asymptomatic Research Suggests
The other study , a vaccine trial studied 230 people living with HIV in East and Southern Africa all had received the Moderna vaccine. Of the 71 participants who tested positive for COVID and were later confirmed to have the Omicron variant, 27 per cent were asymptomatic. A previous portion of the study, which had looked at people in the same region during South Africas Beta outbreak, had found an asymptomatic rate of between one and 2.4 per cent.
As we witness the quick, global spread of omicron, it is clear that we urgently need a better understanding of the transmission dynamics of this variant, Dr. Lawrence Corey, senior author of the study, said in a press release .
The South African study is one of several aiming to discover how and why the newest variant spreads so rapidly. Omicron appears to be much more contagious than previous variants, even among people who are fully vaccinated. A recent Danish study suggested it may be due in part to the way the virus can elude our immune systems.
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No Symptoms Means You Feel Your Best
Defined by the CDC as when a person is infected with a virus and will never feel any symptoms at all, asymptomatic has become a catchall phrase for those who feel fine and arent exhibiting any of the common markers of Covid-19 lack of taste or smell, dry cough, fever but still test positive and appear to be capable of spreading the virus.
In the age of omicron, when symptoms can be almost imperceptible, asymptomatic means absolutely no sniffles, coughs, or aches of any kind. Asymptomatic means you feel in your best shape ever, says Jorge Salinas, an assistant professor of medicine and hospital epidemiologist at Stanford University. You are doing great. You feel amazing, nothing bothers you.
Because community transmission is so high right now, its best to assume youve been exposed to someone who has Covid-19 if youve been to a public place recently, Salinas says. Everyone should act as though theyve come in contact with the virus and are potentially infected, and if anything feels off beyond your normal aches and pains , you should consider it a symptom.
Tolerance for pain or illness varies from person to person what one person considers a mild cold might feel like a more disruptive flu to another and a little throat tickle may not ping as sick to you in ordinary circumstances. But these arent ordinary circumstances. No matter the severity, any cough, sneeze, headache, or body ache should be viewed as a symptom.