Data to guide the application of the new WHO criteria for releasing COVID-19 patients from isolation

On 17 June 2020, the World Health Organization released an update on their recommendations on the criteria for releasing COVID-19 patients from isolations [1]. In the new update, the criteria required to release a symptomatic patients are 3 days without symptoms after 10 days from symptom onset (symptoms include fever and respiratory symptoms). The authors acknowledge the possibility that patients released from isolation with these criteria may still test positive for the COVID-19 virus (SARS-CoV-2) by RT-PCR, but they consider unlikely that they would be able to transmit the virus to another person.

Since 23 March 2020, we have monitored and are still monitoring patients discharged from the Luigi Sacco Hospital of Milan during their home isolation through the Operations Center for Discharged Patients (COD19). COD19 is an active surveillance service for home-care patients operated by resident doctors via phone calls. At discharge, patients are provided with hydroxychloroquine and lopinavir/ritonavir therapy, and a thermometer and a pulse oximeter for parameter monitoring. Parameters are collected once or twice a day, and include body temperature, oxygen saturation at rest and after 6-minute walk test, respiratory rate, and COVID-19 related symptoms. The service also serves as the reporting service for patients ready to be tested for release. The criteria currently enforced require all confirmed COVID-19 diagnosis 2 negative swab tests after 14 days without symptoms.

To put in context the updated WHO recommendations, we share the results of swab test performed after an accurate assessment of 14 days without symptoms on patients with a confirmed COVID-19 diagnosis. Of 314 confirmed diagnosis, 226 (72·0%) tested negative after 14 days without symptoms, 54 (17·2%) tested weak positive, and 34 (10·8%) tested positive for the COVID-19 virus. Fig. 1 shows after how many days from symptom onset those swab were performed. Positive tests were obtained with a minimum of 14 days from symptom onset to a maximum of 73 days, with a median of 33 days. While most patients tested negative or weak positive, the markedly positive results found in almost 11 % of our sample may cause some concern, also considering that stricter criteria (14 days vs. 3 days) were applied in this case.

Fig. 1.

Frequency of swab results (binwidth = 5 days).

These data can guide countries who may choose to continue to use testing as part of the release criteria of patients with confirmed COVID-19 diagnosis.

Funding statement

The surveillance was funded by Fondazione Romeo ed Enrica Invernizzi. The funding agency had no influence in the publication of this letter.

Declaration of Competing Interest

All authors declare no conflict of interest.