London, Oct 29 (IANS): Researchers have reported that some patients recovered from Covid-19 could still carry the virus, suggesting that recovered patients should be more cautious and avoid close contact with others.

According to the study, published in the American Journal of Preventive Medicine, close to 17 per cent of patients considered fully recovered from Covid-19 tested positive for the virus in follow-up screening.

Patients who continued to have respiratory symptoms, especially sore throat and rhinitis, were more likely to have a new positive test result.

This suggests the persistence of these two symptoms should not be underestimated and should be adequately assessed in all patients considered recovered from Covid-19.

"Clinicians and researchers have focused on the acute phase of Covid-19, but continued monitoring after discharge for long-lasting effects is needed," said study lead author Francesco Landi from Catholic University of the Sacred Heart in Italy.

The study included 131 patients who met the World Health Organization (WHO) criteria for discontinuation of quarantine at least two weeks prior to the follow-up visit.

The WHO criteria specify that the patient should be fever-free without fever-reducing medications for three days, show improvement in any symptoms related to Covid-19, be more than seven days past symptom onset, and test negative for the virus twice, with reverse transcription PCR (RT-PCR) testing.

A new RT-PCR test was administered at the time of post-acute care admission.

Demographic, medical, and clinical information was collected, with an emphasis on the persistence of symptoms and signs related to Covid-19 such as cough, fatigue, diarrhoea, headache, smelling disorders, loss of appetite, sore throat, and rhinitis.

The findings showed that 16.7 per cent of the patients tested positive again. There was no significant difference between patients with positive and negative test results in terms of age or sex.

None of the patients had a fever and all reported improvement in their overall clinical condition.

Time since onset of disease, number of days hospitalized, and treatments received while hospitalised were not significant.

The only two symptoms that were higher and significantly prevalent in patients with a positive test were sore throat (18 per cent vs four per cent) and signs of rhinitis (27 per cent vs two per cent).

"Our findings indicate that a noteworthy rate of recovered patients with Covid-19 could still be asymptomatic carriers of the virus," Dr Landi observed.