Asymptomatic patients have higher SARS-CoV-2 viral loads than symptomatic patients, study says

By Angela Betsaida B. Laguipo, BSNNov 29 2020

The coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread across the globe. To date, there are over 62.6 million infections and more than 1.45 million related deaths recorded globally.

Many studies have shown that asymptomatic carriers can spread the virus even if they do not manifest any symptoms, such as fever and cough.

Now, a surprising new study shows that asymptomatic COVID-19 patients have greater viral loads than those with symptoms.

A team of researchers aimed to evaluate the viral loads of six different sample types of patients of different ages and clinics to determine the relationship between disease course and SARS-CoV-2 viral load.

Study: Higher viral loads in asymptomatic COVID-19 patients might be the invisible part of the iceberg. Image Credit: NIH

COVID-19 - a challenging disease

The coronavirus pandemic first emerged in Wuhan City, China, in late December 2019. From there, it has spread to over 191 countries and territories.

On January 7, 2020, the causative agent was identified in humans and was named SARS-CoV-2. By March, the World Health Organization (WHO) declared COVID-19 as a pandemic.

COVID-19 is a challenging disease. As the disease evolves, new information emerges. For instance, COVID-19 was first described as a respiratory tract infection. However, as the virus spread across the globe, many patients manifested other complications. The SARS-CoV-2 infection also causes systemic inflammation and thrombosis.

Though some people experience severe disease, the majority of patients only develop mild to moderate symptoms. In some cases, they do not manifest any symptoms at all. Called asymptomatic carriers, they contribute to the vast spread of the illness.

What the study found

The study, published in the journal infection, highlights the role of asymptomatic spread in the coronavirus pandemic.

To arrive at the study findings, the researchers collected nasopharyngeal, oropharyngeal, oral cavity, rectal, saliva, urine, and blood samples from patients who were hospitalized due to COVID-19.

A total of 360 samples from 60 patients were obtained upon admission. Of these, 25 percent did not have symptoms, while 75 percent were symptomatic.

The Public Health Institute of Turkey Virology Reference and Research Laboratory analyzed the samples.

The researchers found that vital loads of asymptomatic patients were higher when compared with symptomatic patients. Further, the viral load had a negative trend with increasing age, while a significant decrease in viral loads was seen with increasing disease severity.

“This study demonstrates that asymptomatic patients have higher SARS-CoV-2 viral loads than symptomatic patients, and unlike in the few study in the literature, a significant decrease in viral load was observed with increasing disease severity,” the researchers wrote in the paper.

The team noted that factors tied to a poor prognosis, including bilateral ground-glass opacity in chest X-ray, low lymphocyte count, and older age, are correlated with low SARS-CoV-2 viral load.

“COVID-19 is a complicated puzzle with pieces of many colors and shapes. Further, virologic and immunological studies are urgently needed to put all the pieces together and see the big picture,” the researchers added.

Asymptomatic patients are known to spread the virus without them knowing they are infected. This makes it harder for countries to control the spread of the virus.

To date, some countries have reported second waves of infection. The United States reports over 13.35 million confirmed infections and more than 266,000 deaths.

Other countries with a high number of cases include India, with over 9.39 million cases, Brazil, with more than 6.29 million cases, France, with at least 2.27 million cases, and Russia, with more than 2.24 million cases, among others.

Mexico reports more than 1.1 million confirmed cases, and a staggering 105,000 deaths tied to the infection.

With the winter season fast approaching in the northern hemisphere, health experts warn that surging cases will be reported over the coming weeks. They firmly advise people to avoid crowds, maintain a distance from others, wear masks, and practice regular hand hygiene.

With many people not exhibiting symptoms of the infection, staying cautious around others is crucial to prevent being infected with the virus.