A review of the recent studies suggested that asymptomatic Covid-19 patients and those with mild symptoms may not be infectious for more than 10 days.

The review, conducted by researchers at Oregon Health and Science University and Oregon State University, was published in the journal Infection Control and Hospital Epidemiology.

The review looked at over 75 studies and concluded that people who are critically ill from the virus can transmit SARS-CoV-2 for as long as 20 days.

The review is in line with the guidelines formulated by the US Centers for Disease Control and Prevention (CDC).

The authors wrote in their analysis: “Detection of viral RNA may not correlate with infectivity since available viral culture data suggests shorter durations of shedding of viable virus. Additional data is needed to determine the duration of shedding of viable virus and the implications for risk of transmission.”

Co-author Monica Sikka, MD, assistant professor of medicine (infectious diseases) in the OHSU School of Medicine stated: “Even though people can shed virus for a prolonged period of time, the studies we reviewed indicated that live virus, which may predict infectiousness, was only detected up to nine days in people who had mild symptoms.”

For the review , the researchers took into account 77 studies worldwide, including 59 that had been peer-reviewed.

All the studies that were analysed reported assessments of viral shedding using standard methods to identify the virus by replicating it through a process called a polymerase chain reaction, or PCR.

“Although PCR positivity can be prolonged, culture data suggest that virus viability is typically shorter in duration,” the authors added.