By Emma Farge

GENEVA (Reuters) – A World Health Organization official on Tuesday described the COVID-19 pandemic as “one big wave” and warned against complacency in the northern hemisphere summer since the infection does not share influenza’s tendency to follow seasons.

WHO officials have been at pains to avoid describing a resurgence of COVID-19 cases like those in Hong Kong as “waves” as this suggests the virus is behaving in ways beyond human control, when in fact concerted action can slow its spread.

Margaret Harris repeated that message in a virtual briefing in Geneva. “We are in the first wave. It’s going to be one big wave. It’s going to go up and down a bit. The best thing is to flatten it and turn it into just something lapping at your feet,” she said.

Pointing to high case numbers at the height of the U.S. summer, she urged vigilance in applying measures and warned against mass gatherings.

“People are still thinking about seasons. What we all need to get our heads around is this is a new virus and…this one is behaving differently,” she said.

“Summer is a problem. This virus likes all weather.”

However, she expressed concern about COVID-19 cases coinciding with normal seasonal influenza cases during the southern hemisphere’s winter, and said the Geneva-based body was monitoring this closely.

So far, she said, laboratory samples are not showing high numbers of flu cases, suggesting a later-than-normal start to the season.

“If you have an increase in a respiratory illness when you already have a very high burden of respiratory illness, that puts even more pressure on the health system,” she said, urging people to be vaccinated against flu.

(Reporting by Emma Farge; Editing by Michael Shields, William Maclean)