Health authorities on Thursday said Covid activity in Hong Kong appears to be declining from its peak, but that it would take "a month or two" before reaching a lower level.

The Centre for Health Protection said the percentage of respiratory samples testing positive for the coronavirus and the viral load in sewage samples have gone down in the week ending on May 24, compared to the period between May 11 and 17.

The number of patients seeking medical help for Covid also dropped, the centre said in a statement.

But the centre's controller, Edwin Tsui, noted that coronavirus activity would remain "relatively high" in the meantime.

"Hong Kong has experienced an upsurge in Covid-19 cases since April this year, more than half a year after the last increase in July and August of last year. The current active period is expected," he said.

"Although the activity of Covid-19 has started to decline, with reference to previous data, we expect that it will remain at a relatively high level in the short term, and will take a month or two to gradually decline to a lower level."

Tsui noted XDV and variants descended from it, including NB.1.8.1, have become the most prevalent strains in the SAR, according to genetic analysis.

NB1.8.1 has been assigned as one of the "variants under monitoring" by the World Health Organization, but the body suggested that the risk it posed was low.

To that, Tsui said Covid vaccines currently used in Hong Kong "can effectively prevent infection and severe disease", while urging high-risk individuals to "not take this lightly" and get inoculated with a booster shot.