Four patients, who recovered from the illness and got discharged from a hospital, tested positive for the virus after a period of 5 to 13 days. These are the findings of a small study, which is one of the first to look at what happens after people recover from COVID-19. 

The findings suggest that some recovered patients may still be virus carriers, according to the research team from the Department of Radiology, Zhongnan Hospital of Wuhan University, Wuhan and the Department of Laboratory Medicine, Zhongnan Hospital of Wuhan University, Wuhan.

"Four patients with COVID-19 who met the criteria for hospital discharge or discontinuation of quarantine in China (absence of clinical symptoms and radiological abnormalities and 2 negative RT-PCR test results) had positive RT-PCR (real-time reverse transcriptase-polymerase chain reaction) test results 5 to 13 days later."

"These findings suggest that at least a proportion of recovered patients still may be virus carriers," states a research letter published in JAMA. Although no family members were infected, all reported patients were medical professionals and took special care during the home quarantine. 

"Previous studies on coronavirus disease 2019 (COVID-19) mainly focused on epidemiological, clinical and radiological features of patients with confirmed infection. Little attention has been paid to the follow-up of recovered patients," say researchers. 

All four patients were exposed to the novel 2019 coronavirus through work as medical professionals. Two were male and the age range was 30 to 36 years. 

One hospitalized patient and three patients (all medical personnel) quarantined at home with COVID-19 were treated at Zhongnan Hospital of Wuhan University, Wuhan, China, from January 1, 2020, to February 15, 2020.

"Among 3 of the patients, fever, cough, or both occurred at the onset. One patient was initially asymptomatic and underwent thin-section CT due to exposure to infected patients," according to researchers.

"All patients had positive RT-PCR test results and CT imaging showed ground-glass opacification or mixed ground-glass opacification and consolidation. The severity of disease was mild to moderate,” say researchers.

Antiviral treatment (75 mg of oseltamivir taken orally every 12 hours) was provided for four patients. According to medical experts, all clinical symptoms and CT imaging abnormalities had resolved for three of the patients. The CT imaging for the fourth patient showed "delicate patches of ground-glass opacity".

They were evaluated with real-time reverse transcriptase-polymerase chain reaction (RT-PCR) tests for COVID-19 nucleic acid to determine if they could return to work. 

All four patients had two consecutive negative RT-PCR test results. The time from symptom onset to recovery ranged from 12 to 32 days.

The patients had to fulfill four criteria for hospital discharge or discontinuation of quarantine.

This includes normal temperature lasting longer than three days, resolved respiratory symptoms, substantially improved "acute exudative lesions" on chest computed tomography (CT) images, and two consecutively negative RT-PCR test results, separated by at least one day.

"After hospital discharge or discontinuation of quarantine, the patients were asked to continue the quarantine protocol at home for five days," says the study.

Post recovery, patients and their families were contacted directly, and patients were asked to visit the hospital to collect throat swabs for the RT-PCR tests.

When the RT-PCR tests were repeated 5 to 13 days later, the team found that all were positive. All patients had three repeat RT-PCR tests performed over the next 4 to 5 days and all were positive.

"An additional RT-PCR test was performed using a kit from a different manufacturer and the results were also positive for all patients," the research shows.

"The patients continued to be asymptomatic by clinician examination and chest CT findings showed no change from previous images. They did not report contact with any person with respiratory symptoms. No family member was infected,” the team says in their analysis.

Based on their findings, the researchers recommend that the current criteria for hospital discharge or discontinuation of quarantine and continued patient management may need to be reevaluated. 

"Although false-negative RT-PCR test results could have occurred as suggested by a previous study,  consecutively negative RT-PCR test results plus evidence from clinical characteristics and chest CT findings suggested that the 4 patients qualified for hospital discharge or discontinuation of quarantine."

Since the current research is limited to a small number of patients with mild or moderate infection, the team recommends that further studies should follow up on patients who are not healthcare professionals and who have a more severe infection after hospital discharge or discontinuation of quarantine. 

"Longitudinal studies on a larger cohort would help to understand the prognosis of the disease," says the team.