MANILA - A total of 51 patients in South Korea were re-diagnosed with COVID-19 after recovering from the respiratory disease, according to a report that quoted Seoul officials.

Experts were dispatched to the COVID-19 hotspots of Daegu and North Gyeongsang province, where many of these cases were reported, said public broadcaster KBS.

Blood tests and other measures will examine whether the cases were reinfection or reactivation of the virus, the report quoted Director of the Korea Centers for Disease Control and Prevention (KCDC) Jeong Eun-kyeong as having said.

China and Japan earlier reported suspected cases of COVID-19 re-infection.

Experts say there are several ways discharged patients could fall ill with the virus again, Reuters reported. Convalescing patients might not build up enough antibodies to develop immunity to SARS-CoV-2, and are being infected again. The virus also could be “biphasic,” meaning it lies dormant before creating new symptoms.

Other experts have also raised the possibility of “antibody-dependent enhancement,” which means exposure to viruses might make patients more at risk of further infections and worse symptoms.

• READ: Explainer: Coronavirus reappears in discharged patients, raising questions in containment fight

Philippine Health Secretary Francisco Duque III earlier advised the public to wait for the World Health Organization's take on the issue.

He also noted that a study around 2006 showed that patients who recovered from coronaviruses could develop antibodies that can protect them from getting infected again for 8 to 16 months.

The Philippines as of Tuesday confirmed 3,764 cases of COVID-19, with 177 deaths and 84 patients who recovered.

South Korea, which has been praised for its fast and effective response to the pandemic, has recorded a total of 10,384 coronavirus cases as of midnight Tuesday, with 200 deaths.

• How South Korea flattened the COVID-19 curve

-- With a report from Reuters