Hongkongers have snapped up medicine for diarrhoea and vomiting after cases of the new XBB Omicron strain that causes gastrointestinal problems emerged in the city and over the border.

Montmorillonite Powder, an anti-diarrhoea medicine, became a top trending topic on Chinese social media, and dispensaries in Hong Kong on Wednesday reported that residents had switched to hoarding similar drugs after ones combating fever and flu sold out in December.

Staff at the Hon Hing Dispensary in the border town of Sheung Shui said all Chinese-made anti-diarrhoea medicine was sold out by Tuesday.

Yao Xiaoling, a 30-year-old housewife, said she had visited two dispensaries on Wednesday and finally managed to buy the medicine she was seeking.

“I heard that the new Omicron variant would cause diarrhoea, so I bought four boxes of Ya-Hom powder for my mother just in case,” she said, referring to a Chinese medicine used to treat the symptom.

Coronavirus infections began rising in Hong Kong in early November and after topping 29,000 at the end of last month, they have started to decline. Health officials on Wednesday confirmed 16,423 infections, of which 401 were imported, and 63 related deaths.

The XBB subvariant has already become the dominant strain in Europe and the United States. Medical experts said the current dominant Omicron subvariants in Hong Kong were BA.2 and BA. 5, and that they did not think new strains XBB and BQ. 1.1 would trigger a wave of infections because the city had been exposed to them for a while and had enough immunity.