(CN) — One of the world's leading virologists suspects there is a growing mass of undetected, symptomless cases of the new coronavirus strain due to technical limitations on diagnostic test kits.
Dr. Christian Brechot, president of the Global Virus Network and professor at the University of South Florida, said in an interview that tracking the spread of the coronavirus has been hampered because current diagnostic kits cannot reliably detect cases of the virus in people who recovered from their infection or experienced no symptoms.
The virus, dubbed COVID-19, has been wreaking havoc across the globe, with major outbreaks in China, South Korea, Italy and Iran. The first major documented outbreak was in the Hubei province of China, where approximately 3,000 deaths have been linked to the pathogen. The Chinese government in late January locked down millions of residents in the city of Wuhan and surrounding areas, a quarantine that was unprecedented in scale in modern history.
In the U.S., there have been 10 deaths linked to the virus in Washington state, several of which stemmed from an outbreak at a nursing home in a Seattle suburb. California on Wednesday reported its first death from the virus.
The available diagnostic kits in the U.S. and abroad aim to detect viral RNA molecules in patients' saliva and nasal swabs. The kits are effective at diagnosing active infections, Brechot said. What we don't have yet are serology-based kits that can detect the immune system's antibodies to the virus, a test method that would help identify people who have been exposed to the virus but did not develop severe infection.
"You have these other tests, which are the serology-based assays. Why do none of the countries have this test, which would allow not only testing of how many patients are infected, but also how many have been exposed to virus?" Brechot asked.
The physician and researcher explained that the challenge in developing this second type of test lies in making sure the results do not conflate the new, more deadly coronavirus strain with common coronavirus strains.
"The problem is that each year, we have several coronaviruses that are infecting humans. We just call those the common cold. When you want to detect this new strain, you have cross-reactivity with the other viruses," Brechot noted. "You don't know whether you are detecting COVID-19 or remnant signals of exposure to mundane viruses."
Researchers ran into the same challenge when trying to develop serology-based diagnostics for SARS-1 coronavirus, which generated a 2002-2003 China epidemic that killed more than 700 people.
If the serology-based tests were available, Brechot said, we might be "surprised to find how many individuals" have been exposed to the new COVID-19 strain but "are absolutely healthy and recovered without symptoms."
According to Todd Ellerin, a Harvard professor and infectious disease specialist in Weymouth, a person who is not showing symptoms of COVID-19 "may be shedding the virus and could make others ill." Ellerin wrote in a post on Harvard's web site: "How often asymptomatic transmission is occurring is unclear."
Preliminary research released last month by China's disease control agency indicated the virus caused only mild symptoms in 80% of the 44,000 Chinese cases analyzed. The overall fatality rate was 20 times higher than the flu, however. In the patient group studied between the ages of 60 to 69, the virus killed roughly one in 28 people.