- Coronavirus symptoms are a poor marker of COVID-19 infection, as many people might be asymptomatic or presymptomatic when spreading the illness.
- UK researchers found that more than 75% of the people who tested positive did not show any symptoms on the day of testing. The percentage is even higher for certain symptoms that are commonly associated with COVID-19.
- Other studies have shown that COVID-19 patients are most infectious a few days before the onset of symptoms and a few days after.
The novel coronavirus is raging as many countries brace for the second wave. On Wednesday alone, nearly 675,000 people tested positive for the virus, which is a new record for a pandemic that has already claimed the lives of more than a million people. The virus is incredibly contagious, and many people may spread the illness before developing any symptoms. People are most contagious a few days before the onset of symptoms and a few days after, which is why health officials urge us to keep respecting the only health measures that can reduce the spread. Social distancing, face masks, and frequent hand washing are required to minimize the risk of spreading the virus.
The scary conclusion of a new study from the UK shows why preventive measures should be respected. Researchers from Great Britain analyzed data about COVID-19 testing, finding that well over 75% of those people who tested positive for the novel coronavirus did not show any signs of having the illness.
The study analyzed COVID-19 testing data from the Office for National Statistics, the UK statistics body, looking at a sample of 36,061 individuals who had a COVID-19 test between April 26th and June 27th. “To reduce transmission of SARS-CoV-2, it is important to identify those who are infectious,” the researchers wrote. “However, little is known about what proportion of infectious people are asymptomatic and potential ‘silent’ transmitters.“
The researchers wanted to determine how many people showed symptoms on the day of the test and found that some 625 persons had reported symptoms that may have been consistent with a coronavirus infection on the day of testing.
Of the 115 COVID-19-positive cases, 27 (23.5%) were symptomatic and 88 (76.5%) had no symptoms.
The scientists focused on a few specific COVID-19 symptoms for the study, including cough, fever, and smell and taste loss. When looking for those symptoms, just 16 (13.9%) people reported symptoms, while 99 (86.1%) had no signs that would raise COVID-19 suspicions.
One of the problems with the novel coronavirus is that it lacks specific signs aside from the sudden loss of smell and taste. Even that symptom does not appear in all cases. That’s why the only way to confirm a diagnosis is through a PCR test.
It’s widely believed that 40% to 50% of infected people are asymptomatic and that asymptomatics do not infect as many people as people who show symptoms. But even people who end up developing COVID-19 signs can be infectious in the presymptomatic phase.
The UK study further underscores that idea. Many people who might end up developing COVID-19 symptoms could be infectious without suspecting they’ve been infected themselves.
“COVID-19 symptoms are poor markers of SARS-CoV-2,” the study concludes. “Thus, 76.5% of this random sample who tested positive reported no symptoms, and 86.1% reported none of those specific to COVID-19. A more widespread testing program is necessary to capture ‘silent’ transmission and potentially prevent and reduce future outbreaks.”
The UK research has been peer-reviewed, and it’s available in full here. As with other COVID-19 studies, more research is required before researchers and health experts can draw any definitive conclusions.
While the UK scientists proved that widespread testing might be a key element for reducing transmission, the study also indirectly supports recommendations from public health experts who have devised protocols for containing the infection. Simple things like social distancing, avoiding crowds, avoiding indoor spaces, hand hygiene, and wearing face masks while in public can prevent encounters with silent spreaders who might be infectious and reduce transmission risk.