The swine flu pandemic appears to have peaked for the moment but the virus will return with "a very big surge" in the autumn, the chief medical officer said today.

Sir Liam Donaldson hailed new data as proof of a "pretty firm downturn" in the number of people seeking medical help with H1N1 from a GP. "There's a possibility the virus has had its fill of us for the moment," he said.

The number of people consulting a doctor with flu-like illness had fallen from 155.3 for every 100,000 people to 138.2 for every 100,000, he said. "It's peaked in America, it's peaked in Mexico, it's peaked in Scotland, so why shouldn't it peak here?" About one in every 158 people in England has had flu in the current outbreak and 27 have died.

School holidays and people being away on summer breaks helped explain the apparent decline, said Donaldson, adding: "We don't anticipate it staying down for too long, because we have our own flu season coming up."

Official figures from the Health Protection Agency showed that the number of new cases of swine flu in England last week increased to 110,000, a 10% rise on the previous week. About 150,000 people were also given the antiviral drug Tamiflu after contacting the National Pandemic Flu Service, which began operating last Thursday. The Department of Health said an overlap between the two groups of patients meant it should not be concluded that 260,000 people were sick with the virus last week.

Indications that the spread of swine flu appeared to be slowing were supported by the latest figures for Scotland, where the H1N1 outbreak first began in the UK. The rate of cases was slightly higher than last week, at 5.5 for every 100,000 people.

Health officials said that about 1,500 new cases were detected by doctors last week, compared with about 1,200 in the previous week, but the number of people consulting doctors had increased.

Four more people in London have died after having swine flu, taking the total fatalities in the capital to 15, it emerged yesterday. Only brief details were released, but NHS London said that the victims all had underlying health conditions and had tested positive for the H1N1 virus.

Meanwhile, a 16-year-old British schoolgirl is fighting for her life in a Greek hospital after contracting the virus. Natasha Newman, from Highgate, north London, is in a "very serious" condition in Athens after becoming sick while holidaying on the island of Kefalonia.

Dr Zoe Beka, from the Penteli Children's hospital, said: "She is receiving different treatments including Tamiflu and antibiotics. There is no doubt that she contracted the illness while in London, but there was a delay in her receiving treatment."