April 16 (UPI) -- A significant number of people with COVID-19 may also be infected with other viruses, a new analysis indicates. The findings highlight the challenges of diagnosing and tracking the new coronavirus, experts say.
In a report published Wednesday by JAMA Network Open, researchers at Stanford University School of Medicine report that they tested more than 1,200 people for COVID-19, and found that 116 people were infected. Of these, more than 20 percent also tested positive for another virus, rhinovirus -- the pathogen that causes the common cold -- as well as enterovirus and respiratory syncytial virus, or RSV, both of which are fairly common in children.
In addition, several simultaneously tested positive for another coronavirus, which suggests that SARS-CoV-2, the virus that causes COVID-19, may be more closely related to other viruses in the family than originally thought.
"As is true for a lot of infectious diseases, with SARS-CoV-2 you may have multiple pathogens and diseases," Caroline Buckee, associate director of the Center for Communicable Disease Dynamics at Harvard T.H. Chan School of Public Health, said in a conference call with reporters. She was not involved with the Stanford study.
"The question is, how do we make sense of that with this outbreak?" she added.
In all, the researchers tested 1,217 nasal and throat swabs for SARS-CoV-2 and other respiratory pathogens from 1,206 unique subjects in the northern California area. Of these, 116 of the specimens, or roughly 10 percent, were positive for SARS-CoV-2 while 318, or 26 percent, were positive for one or more other viruses.
Of the 116 specimens positive for SARS-CoV-2, 21 percent, were positive for at least one more virus. The most common "co-infections" were rhinovirus and enterovirus at 7 percent, RSV at 5 percent, or another coronavirus at just over 4 percent.
The authors emphasized that the findings may be unique to the region. They noted, however, that the results "suggest that routine testing for non-SARS-CoV-2 respiratory pathogens during the COVID-19 pandemic is unlikely to provide clinical benefit unless a positive result would change disease management."
The new study was released days after the U.S. Centers for Disease Control and Prevention released its final FluView report for the 2019-20 winter season. In it, the agency said its estimates for flu cases, hospitalizations and deaths -- 39 million cases, 410,000 hospitalizations and 24,000, respectively -- were likely impacted by the COVID-19 outbreak in some parts of the country, particularly toward the end of the winter.
More than 638,000 Americans have tested positive for the disease caused by the new coronavirus, and 31,000 have died. Buckee doesn't expect that the final numbers for the disease toll will "change wildly" once any crossover between COVID-19 and seasonal flu is accounted for.
"The PCR assays being used are quite specific and they can, and will, easily differentiate flu and the SARS-CoV-2," Stephen S. Morse, a professor of epidemiology at Columbia University's Mailman School of Public Health, told UPI. "However, we aren't able to test and characterize as many flu isolates as we'd like, and testing is extremely limited for SARS-CoV-2."
While the CDC's test for the new coronavirus "seems to work pretty well," according Morse, delays in rolling out an accurate version of the kits -- and the fact that "most infected individuals are mildly ill or asymptomatic" -- means that many cases may have been missed or misdiagnosed, perhaps as flu, given that the two share common symptoms, including cough and fever.
COVID-19 also progresses much slower than the flu, Morse adds, with most people not experiencing symptoms until one to two weeks after they were actually exposed to the virus.
"Since we're only really diagnosing clinical cases of disease that come to medical attention, we're identifying only a relatively small fraction of the infections," he explained. "This virus is probably circulating around for weeks before we identify our first 'case.' Failing to understand this distinction -- together with much too little testing capacity -- led to a fatally flawed testing and control strategy that put us where we are today."