Public alarm about swine flu rose yesterday, with callers swamping the telephone advice service NHS Direct to seek information about the disease.

The news came as the Government's chief medical officer, Sir Liam Donaldson, said that up to a third of the population may catch swine flu this winter and that the virus could be around for up to five years.

Operators answered 9,060 calls about swine flu, the highest number in a single day, following the death of a six-year-old London schoolgirl, Chloe Buckley. The parents of the girl, who died 48 hours after catching swine flu, said they were satisfied with the care she had received. Early reports suggested she had initially been diagnosed with tonsillitis and sent home, before her condition worsened.

Her parents, Michael and Jacinta, from West Drayton, issued a statement expressing their distress at the loss of "our fun-loving baby girl" and asked to be left to grieve in peace. "We are satisfied that the medical care Chloe received at all times was appropriate, and are disappointed with the stories that suggest otherwise," the statement said.

A post mortem was being carried out to establish the exact cause of her death.

Michael Day, a 64-year-old GP from Bedfordshire who had been infected with swine flu before his death on Saturday, did not die from the disease, a post-mortem report revealed yesterday. It stated that he died from "natural causes". Reports suggested he suffered from heart disease and high blood pressure and gave the cause of death as a blood clot in his lungs.