In a small study conducted in China, many patients with mild cases of COVID-19 infection continued to test positive for the virus up to 8 day after their symptoms had resolved, according to a research letter published in the American Journal of Respiratory and Critical Care Medicine.
“The most significant finding from our study is that half of the patients kept shedding the virus even after resolution of their symptoms,” Lokesh Sharma, PhD, instructor of medicine in the section of pulmonary, critical care and sleep medicine at Yale School of Medicine, said in a press release. “More severe infections may have even longer shedding times.”
The study included 16 patients with COVID-19 who were treated and released from the Treatment Center of PLA General Hospital in Beijing from Jan. 28 to Feb. 9. Patients ranged in age from 3 to 68 years, with a median age of 35.5 years, and 11 of 16 were male.
For the study, Sharma and colleagues collected and analyzed throat swabs on alternative days. Patients were discharged after recovery and confirmation of negative status by at least two consecutive real-time polymerase chain reaction (PCR) results.
Major symptoms included fever, cough, pharyngalgia and dyspnea.
Treatment varied among patients and included alpha-interferon as well as other antiviral drugs, including oseltamivir, lopinavir/ritonavir, acyclovir, moxifloxacin, methylprednisolone, gamma globulin, vancomycin and meropenem, alone or in combination. One patient required mechanical ventilation.
Incubation periods were estimated based on the patient’s travel or potential exposure. The time from infection to symptom onset was 5 days in all but one patient who had no specific exposure, according to the results. Symptom lasted for an estimated average of 8 days. Notably, however, eight of 16 patients continued to test positive for COVID-19 for 1 to 8 days after symptom resolution.
The researchers noted that two patients had diabetes and one had tuberculosis, but neither comorbidity affected the time course of disease. The same was true for the youngest patient, aged only 3 years.
“If you had mild respiratory symptoms from COVID-19 and were staying at home so as not to infect people, extend your quarantine for another 2 weeks after recovery to ensure that you don’t infect other people,” Lixin Xie, MD, professor at the College of Pulmonary and Critical Care Medicine at the Chinese PLA General Hospital in Beijing, said in the release.
Additionally, both Sharma and Xie stated in the release that patients with COVID-19 “can be infectious even after their symptomatic recovery, so treat the asymptomatic/recently recovered patients as carefully as symptomatic patients.”
Importantly, the researchers noted that this study was small and included patients with milder infections who recovered from the disease. It remains unclear, they added, whether the more vulnerable population, such as older patients, those with immune deficiencies or those on immunosuppressive therapies, would have delayed viral clearance.
“Further studies are needed to investigate if the real-time PCR-detected virus is capable of transmission in the later stages of COVID-19 infection,” Xie said. – by Melissa Foster
Disclosures: The authors report no relevant financial disclosures.