Asymptomatic individuals are the biggest problem in the COVID fight
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease (COVID-19), affects people differently. Some people may experience mild to moderate symptoms, while others may require hospitalization due to severe symptoms. Others may not develop symptoms at all.
These people, known as asymptomatic carriers, can pass the virus on to others without knowing it. Since the pandemic began in December 2019, the asymptomatic spread has contributed to exploding cases.
Researchers at the Georgetown Center for Global Health Sciences and Safety at Georgetown University in Washington report that the lack of testing on asymptomatic carriers makes it difficult to control the spread of SARS-CoV-2.
Transmission without symptoms
The researchers found in a study published in the journal Science that asymptomatic cases are those in which no symptoms occur during the duration of the infection. In contrast, presymptomatic cases develop symptoms later in the course of the infection. These two groups of people are key drivers of transmission.
Symptom-free transmission poses challenges in identifying the infectious schedule and possible exposures. Not knowing they are infected, they can likely mix with others and encourage the spread of viruses. You may also fail to adhere to masking, distancing, hand hygiene, and staying at home.
Although the prevalence of asymptomatic cases is not accurately reported, early studies showed that these cases accounted for about 30 to 80 percent of infections. Recent evidence reports a rate of asymptomatic cases between 17 and 30 percent.
To contain Covid, we need to put out the “smokeless fires”. This brief review of the asymptomatic status, what we need to know and what action is required is exceptional. From @angie_rasmussen and @SaskiaPopescu @ScienceMagazine today with @ScienceVisuals https://t.co/Ak4hc2TwuF pic.twitter.com/3mFq2TZtUH
– Eric Topol (@EricTopol) March 18, 2021
Evaluation of the secondary transmission
As important as assessing the prevalence of asymptomatic infections, it is important to determine the risk of secondary transmission. Contact tracing is based on identifying cases where people with symptoms are being tested. If a person tests positive for SARS-CoV-2, all contacts are checked for possible infections.
However, when it comes to asymptomatic cases, it will be difficult to identify close contacts. Surveillance tests to analyze secondary attack rates, the percentage of cases that come from an infected person in a group, are very difficult.
The real effect of asymptomatic spread
In COVID-19 patients with symptoms, the infection period begins two days before symptoms appear and a few days after. There is also decreased virus excretion within the first week of symptoms appearing.
In asymptomatic cases, the kinetics of virus shedding is not well understood. During early infection, people have similar viral loads regardless of the severity of symptoms. People without symptoms have reduced peak replication titers and faster virus clearance, which shortens the infection period.
Therefore, measuring the real effects of asymptomatic spread is critical, although this can be confusing. Some studies showed that asymptomatic people were 42 percent less likely to transmit the virus and had lower rates of secondary attacks. Other studies have found that despite the shorter infection period, virus transmission is similar in patients with presymptomatic or asymptomatic SARS-CoV-2 infection.
The researchers also found that people with symptoms may have higher rates of secondary attacks, but they are the most likely to undergo testing and self-isolation. People without symptoms can prevent transmission by following public health measures to prevent infection. These include wearing face masks, washing your hands regularly, promoting ventilation, and social distancing.
“With many contagious people without symptoms and with no reliable surveillance tests for asymptomatic or presymptomatic infections, it is critical to maximize efforts to reduce the risk of transmission in the community,” the researchers found in the study.
They added that the lack of testing and isolation of asymptomatic cases could lead to an increase in cases. Governments must do extensive testing and monitoring to detect those without symptoms. This will adequately isolate infected people, reducing the risk of virus transmission.
“Until a full implementation of robust surveillance and epidemiological measures is in place to enable us to put out these smoke-free fires, the COVID-19 pandemic cannot be completely erased,” the team added.
Currently, the number of confirmed SARS-CoV-2 infections worldwide has exceeded 123 million, with over 69 million reported as recovered.