LONDON — A leading epidemiologist whose work heavily influenced Britain’s lockdown measures said the coronavirus outbreak in the U.K. is unlikely to worsen during the summer but that the outlook from September was “very unclear.”

Professor Neil Ferguson from Imperial College London said he expects levels of coronavirus transmissions and cases to “remain relatively flat between now and September, short of very big policy changes or behavior changes in the community.”

He told a committee of lawmakers in the House of Lords on Tuesday that the “real uncertainty” will be in September, a time of year when respiratory viruses tend to start transmitting more forcefully.

Ferguson resigned from his position as a government adviser last month after revelations that he broke social distancing rules.

Ferguson leads a team which modeled the spread and impact of the coronavirus. The team's data was instrumental in prompting Prime Minister Boris Johnson to impose the lockdown on March 23.

The lockdown is being eased across the U.K., most quickly in England, raising concerns among many health officials of a potential second spike in infections.