H1N1 swine flu is the dominant strain of the virus this year, say health experts. the majority of victims have had underlying health problems. Photograph: Lewis Whyld/PA

The Health Protection Agency has confirmed H1N1 swine flu is the dominant strain of the virus this year and that 10 people in the UK have died from it in recent weeks.

Doctors have urged those most at risk to visit their GP to receive a vaccine.

This year’s vaccine protects against three strains of flu, including H1N1. the Health Protection Agency (HPA) said the majority of victims this year had underlying health conditions. High-risk groups include expectant mothers and people with chronic conditions, such as lung and heart disease.

The HPA said: “The flu H1N1 (2009) virus, formerly known as swine flu, is now one of the group of seasonal flu viruses circulating around the world. Following a pandemic it is often the case that the pandemic strain becomes the most common seasonal strain of influenza the next flu season, so it in not surprising to see H1N1 (2009) circulating this winter.”

A spokeswoman said “a small proportion” of those who died from the virus this year had previously been in good health.

In Greater Manchester two men have died at the Royal Oldham hospital after contracting swine flu. NHS Oldham said the patients, both from the town, had underlying illnesses.

The director of public health for Oldham, Alan Higgins, said swine flu had been a factor in the deaths of the men. He added: “Those at greater risk of developing serious complications from flu should contact their local GP as soon as possible to arrange a flu jab to protect themselves from the virus.”

The deaths come at a time when the number of flu-related visits to GPs is low. Consultations about flu-like symptoms in England last week were 13.3 per 100,000 of the population.

Professor John Watson, head of the respiratory diseases department at the HPA, said: “Over the last few weeks we have seen a rise in the number of cases of seasonal flu, including both H1N1 (2009) and flu B, in the community. we have also received reports of patients with serious illness requiring hospitalisation, and outbreaks of flu in schools across the country.

“For most people flu is not life-threatening and usually lasts seven to 10 days. however, it can be far more dangerous for those in at-risk groups, such as the elderly, pregnant women and patients with heart problems, diabetes or lung, liver or renal diseases, or those who have weak immune systems, who are at risk of developing complications.”

He said vaccination offered the best protection for those at high risk from seasonal influenza. “Although unpleasant, flu is a self-limiting illness and if you have flu it is best to stay at home until well,” he said.

“If individuals in at-risk groups develop symptoms consistent with flu, or anyone whose symptoms persist or become more severe, then we advise they should seek medical advice.”

Professor David Salisbury, director of immunisation at the Department of Health, said: “These figures demonstrate that the effects of flu are not to be underestimated. It is not the same as getting a cold and can seriously affect your health. the seasonal flu jab protects against the dominant strains … including the type known as swine flu.”

A patient is in intensive care at Southport and Formby district general hospital after contracting swine flu. the patient is expected to be transferred to another hospital for specialist treatment.

A spokesman for the Southport and Ormskirk NHS Trust said it had admitted a number of patients since mid-October with the H1N1 virus.