Boy’s infection was genuine: Yuen Kwok-yung

Microbiologist Yuen Kwok-yung on Thursday rejected suggestions that a four-year-boy had tested false positive for the coronavirus, saying his infection should be treated as genuine.

The boy developed a fever and sore throat on May 12. He was taken to a private doctor in Tsing Yi the following day and a Covid-19 test was ordered.

On May 15, health authorities said the boy was infected and they didn’t know how he had caught the virus.

However, he repeatedly tested negative for the virus afterwards, nor did he carry the antibodies for it, leading to speculation that his case was a false positive.

But speaking to reporters after inspecting the laboratories that processed the four year-old’s deep throat saliva sample, Yuen said he didn’t believe the sample had been contaminated.

A separate test by the University of Hong Kong also confirmed the infection, he added.

The expert said the boy could have been caught the virus from his neighbours at Pak Tin Estate all the way back in January, but showed no symptoms all along.

“About 20 percent of the patients who didn’t display symptoms also won’t generate antibodies. It’s also possible they continue to release residues of the virus for several months,” he said.

The second possibility, the microbiologist added, was that the boy was infected by both Covid-19 and another virus.

“That would have led to a high CT value, which means a low viral load. The interference by the other virus could also delay the body from generating antibodies, or it may never appear.”

To play safe, Yuen said the 34 people who had been classified as the boy’s close contacts have to remain in quarantine.

The latest discovery dashed hopes that Hong Kong could soon reach the target of 28 days with no untraceable infections.