What Are Mild COVID-19 and Asymptomatic (Symptom-free) Disease? Can a Person Become Infected a SECOND TIME?
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Unfortunately, despite all the precautions taken, the number of deaths worldwide from COVID-19 continues to rise. People presenting to hospitals usually have high fever, fatigue and a dry cough; nasal congestion, loss of smell, sore throat, myalgia (muscle pain) and diarrhea may be other symptoms. Most patients develop symptoms within 3-7 days.
Is It Possible to Contract COVID-19 and Even Recover Without Symptoms?
Yes, it is possible. Studies suggest that more than 80% of all COVID-19 cases involve patients who have no symptoms (asymptomatic) or experience mild illness.
The first point to emphasize is that a person can carry COVID-19 without showing any symptoms; such people are even called silent carriers and are the main people spreading the disease. Contact with others, particularly people identified as being in risk groups, may cause no problems for the asymptomatic patient (silent carrier) but can cause serious health problems in others and may even result in death.
-Related topic: How Can the Same Virus Cause No Symptoms in One Person but Death in Another?
Researchers identify the main reason for the virus’s very rapid worldwide spread as people without symptoms failing to follow isolation rules. For this reason, pay attention to social isolation!
How Can You Tell Whether You Are a Silent Carrier?
Being a silent carrier means having no symptoms, so it cannot be identified through examination or self-observation. If you have had contact with someone known to be ill, work in crowded settings, have been in such settings without protection, or are a healthcare worker, you may be a silent COVID-19 carrier. To protect yourself, you can avoid leaving home as much as possible, follow social distancing rules, wear a mask and wash your hands frequently. If, in the future, safe and effective antibody tests become widespread, it may become easier to identify who has and has not had the disease.
Scientific Studies on Silent Coronavirus Carriers
In a recent statement, Mi Feng, spokesperson for China’s National Health Commission, said that among 6764 people who tested positive for SARS-CoV-2 and were followed up, 1297 developed symptoms in subsequent days. He added that 1023 were being kept in medical isolation to see whether they would develop symptoms, while the remaining 4444, who had shown no symptoms, were released from medical observation once their tests for the virus became negative.
These 6764 positive cases were detected by testing people who had been in contact with previously confirmed COVID-19 cases. In this context, the number of asymptomatic carriers may be much higher, because people without symptoms do not seek testing. This makes it almost impossible to determine the actual proportion of asymptomatic carriers. However, the passenger ship ‘’Diamond Princess’’ may have allowed scientists to study the issue. Studies on the ship, which was quarantined for more than two weeks in February, produced statistical models suggesting that 18% of infected people developed no symptoms. An important point is that the average age on the ship was higher than in the general population. Since older individuals tend to have more severe illness and are more likely to show symptoms, it is thought that asymptomatic carriers (those with no symptoms) may account for 30-40% of the general population. Robert Redfield, director of the US Centers for Disease Control and Prevention (CDC), recently gave this proportion as 25% without citing a reference.
Although the novel coronavirus (SARS-CoV-2) has 80% homology (similarity) with SARS-CoV, there are substantial differences in the illnesses they cause.
During the SARS outbreak in 2003, viral infectiousness was greatest (when the viral load in the respiratory tract was highest) 10 days after symptoms appeared, and the viral load in the upper respiratory tract was low in early infection. This may be one reason why the SARS outbreak could be controlled. New England Journal of Medicine reported a study finding that, in COVID-19 caused by SARS-CoV-2, viral load peaks immediately after symptoms begin. In the same study, one of the 18 patients examined was asymptomatic and had a viral load similar to the other 17. Other studies emphasize that infectiousness begins before symptoms appear.
How long the virus continues to spread after symptoms disappear remains a mystery.
These questions will remain unanswered until comprehensive studies are conducted in large patient groups using sound scientific methodology. At this stage, the most sensible thing everyone can do is consider themselves a carrier of the novel coronavirus and protect themselves and those around them by observing all social isolation recommendations from relevant experts.
Is It Important to Identify Patients Who Have COVID-19 Without Symptoms?
Certainly! We now know clearly that the novel coronavirus (SARS-CoV-2) spreads mainly through silent carriers. The countries with the lowest COVID-19 death rates are those that test as many asymptomatic patients as possible, isolate them and prevent or slow transmission to older people (see Singapore).
Identifying silent carriers is also important for the experimental convalescent (recovered-patient) plasma therapy discussed in our other articles. Let us briefly recall what we know about this treatment;
Most patients who contract COVID-19 develop immunity to the virus. In other words, against the risk of encountering the virus again, the individual produces IgG antibodies that attack and neutralize it and keeps them ready in the plasma portion of the blood.
As can be seen above, if a person’s immune system can develop IgG antibodies against the infection (red line), that person recovers, and these IgG antibodies may protect against subsequent infections (depending on their neutralizing properties and how long they remain at high levels). Rapid antibody tests for SARS-Cov-2 can establish whether a person has had COVID-19.
Can I Catch COVID-19 Again After Recovering Once?
Unfortunately, it currently seems difficult to give a clear answer. When our body encounters the virus, our immune system begins producing antibodies, eliminating the virus while the antibodies in our plasma also protect us against future infections. In theory! Unfortunately, the situation is more complicated. Some viruses, such as those causing chickenpox and measles, produce immune responses resulting in lifelong protection. This is not the case with viruses such as HIV. Regarding SARS-CoV-2, George Rutherford, head of Infectious Diseases and Global Epidemiology at the University of San Francisco, says there are still many unknowns about our immune responses to the virus and that we need more time to learn the facts. Two important questions must be answered to determine whether people who recover can contract COVID-19 again: How long do antibodies produced by immune cells against SARS-CoV-2 remain in the body, and how long does their protection last?
David Walt, a professor of pathology at Harvard Medical School and Brigham and Women’s Hospital in Boston, states that there is no evidence that the antibodies produced will also be protective in the future and emphasizes that there is also no scientific evidence that a person will not become infected with SARS-CoV-2 again. Previous studies of other coronavirus types have shown that encountering the virus did not provide adequate protection against future infections. After these concerning statements, Prof. Walt mentions other hopeful developments: "Not all antibodies produced by immune cells are the same. Some recognize the pathogen but cannot bind to it. Others, however, carry out a process called neutralization. After recognizing the pathogen, they bind tightly to it and prevent it from harming us, while helping immune cells destroy it. There is evidence that antibodies produced against SARS-CoV-2 have neutralizing properties. Plasma therapy, which has begun in many places, also shows us this. However, we do not yet know how long this protection lasts." Mike Ryan, executive director of the World Health Organization’s emergency programmes, said at a press conference: "Unfortunately, we do not currently have an answer to this question. However, studies are continuing".
To find the answer, researchers need to take blood samples from individuals at regular intervals and test them. The expected answer can be provided as a result of these studies. Until then, following social isolation rules remains very important, even if you have no symptoms and have recovered from the disease.
Sources
Zou L, Ruan F, Huang M, et al. SARS-CoV-2 Viral Load in Upper Respiratory Specimens of Infected Patients. N Engl J Med. 2020
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