COVID-19 Patients Shed Coronavirus for 17 Days on Average, Study Finds

A group of COVID-19 patients in China shed the coronavirus for 17 days on average, according to a study.

The paper, published in the International Journal of Infectious Diseases,involved 147 patients diagnosed with COVID-19 at Changsha Public Health Treatment Centre. The city of Changsha is the capital of Hunan province, and adjacent to Hubei province, where the pandemic is thought to have started in its capital Wuhan late last year. Since then, the coronavirus has killed more than 318,000 people in 4.8 million known cases worldwide, according to Johns Hopkins University, while more than 1.7 million people have survived. The U.S. has the most known cases in the world, as the Statista graph below shows.

Countries with the most confirmed COVID-19 cases.
Countries with the most confirmed COVID-19 cases. Getty Images

The patients who took part in the study visited the hospital between January 24 and March 8, 2020. To qualify for the study, they had to have tested positive for SARS-CoV-2 (the coronavirus which causes COVID-19) on a known date, and be aged 18 or over. The patients were aged 42 on average, and 54 percent were female. The most common symptoms in this group were a fever and cough. On average, patients had symptoms for six days before they were admitted to the facility. All of the patients took antiviral treatments.

Of the total participants, 86 had moderate COVID-19, defined as having a fever, respiratory tract symptoms, and chest scans which confirmed they had pneumonia. The remaining 14 percent were severe, with conditions including respiratory distress and low blood oxygen levels. The patients were discharged if they hadn't had a fever for over three days, saw a significant improvement in their respiratory tract symptoms and lung scans, and two negative coronavirus tests over a 24-hour period.

After studying the patients' medical records, the researchers noted the length of time between patients reporting their first COVID-19 symptoms and their negative SARS-CoV-2 test. On average, it took 17 days for patients to test negative. The time of shedding ranged from six to 47 days in one patient.

The team pinpointed certain variables which were linked to patients shedding (where a virus replicates in the body and can be passed on) the bug for over 17 days. They found those with the highest temperature, at 38.3 degrees Celsius (100.94 degrees Fahrenheit) on average, patients who stayed in hospital longest, and those who had symptoms for a longer period before they were admitted to hospital appeared to shed the virus for a longer period. Patients who coughed up blood were more likely to shed for over 17 days.

However, there was no link between age, sex, BMI, exposure history to the coronavirus or underlying conditions and the length of shedding.

Ian Jones, professor of virology at the University of Reading who did not work on the study, told Newsweek: "This study on virus shedding formalises what is generally known, that patients shed virus for 2 to 3 weeks and that, broadly speaking, the sicker the patient the more virus they release.

"While there are no surprises in what is reported, the data reinforce the point that the sooner a patent is treated, the better the outcome, both for the patient and those around them. Testing and isolation, much discussed as a control strategy, gets very firm support by the data provided."

The authors acknowledged the study was limited in several ways, including that the sample size was relatively small and most patients had mild symptoms. As the study was retrospective, where scientists look back at existing data, demographic and clinical characteristics as well as laboratory and radiographic findings were incomplete.

The researchers concluded: "Potential risk factors were identified and should be taken into consideration for the strategy of quarantine of infected patients."

The team are among those attempting to shine a light on how the little understood coronavirus interacts with our bodies. In March, a separate team concluded COVID-19 patients whose symptoms have cleared can carry the new coronavirus for up to eight days. The findings were published in the American Journal of Respiratory and Critical Care Medicine.

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A nurse talks with a driver before taking a sample at a COVID-19 drive-thru test point, in Bogota, Colombia, on May 14, 2020. JUAN BARRETO/AFP via Getty Images