Patients retesting positive after having recovered from novel coronavirus disease (COVID-19) are not contagious, a Vietnamese expert has said.

They cannot transmit the pathogen because their body simply contains the remains of the virus after their recovery, said Nguyen Van Kinh, former director of the National Hospital for Tropical Diseases in Hanoi.

Vietnam’s Ministry of Health requires that those retesting positive be isolated and treated like new patients.

Those having recovered from SARS and MERS-CoV, two respiratory diseases caused by the old strains of the coronavirus, will be completely rid of the pathogen which also exists for a short period of time, Kinh said.

“COVID-19 is similar to the two diseases but the novel coronavirus mutates more frequently,” the expert remarked.

“It takes time for the world to study its pathogenesis and viral immunology.”

A wave of recovered patients retesting positive has been recorded in several countries, including Vietnam with over a dozen cases and South Korea with 260 ones.  

“Such cases didn't exhibit any symptoms and appeared clinically healthy,” Kinh said.

“But their final test still returned positive.”

Vietnam is employing the real-time PCR method to confirm COVID-19 cases, the expert said, adding this test has 98 percent sensitivity.

“Vietnam is among the few countries that can culture and isolate this virus,” Kinh said.

Lab experiments showed that no virus grew again from samples taken from those retesting positive, the expert revealed.

“This proves that tests simply picked up the remains and fragments of the virus during the body’s elimination process,” Kinh concluded.

“Epidemic investigations in China, Vietnam, and Japan have shown that patients declared recovered and later testing positive did not pass the pathogen to others, even when they had contact with their kin.”

The World Health Organization told AFP on Wednesday that recovered patients retesting positive does not constitute a reinfection.

"We are aware that some patients test positive after they clinically recover," a WHO spokesperson told AFP.  

"From what we currently know – and this is based on very recent data – it seems these patients are expelling left over materials from their lungs, as part of the recovery phase."

Vietnam has confirmed 271 cases as of Thursday morning, with 232 recoveries and no documented death, according to the Ministry of Health.

The Southeast Asian country has carried out over 261,000 tests so far, while quarantining more than 34,000 people at the time of writing.

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