The NHS is warning people to be on the lookout for symptoms of the potentially deady "Aussie" flu following a rise in Lancashire cases.
Medical professionals are calling on people to spot the signs and treat them at home as soon as possible to prevent it spreading any further.
Flu viruses fall into one of three categories - A, B and C - and symptoms include: a temperature of 38°C or above; an aching body; a sore throat; headaches; and a loss of appetite.
The "Aussie" variety also goes by the name of H3N2 and is just one of several strains of flu circulating the country this winter.
It is a type A virus, the most severe of the three, and seems to most seriously affect young children and the elderly.
It was given its nickname after recently becoming Australia's biggest outbreak of flu in nearly a decade.
Chief Executive of Lancashire Teaching Hospitals NHS Foundation Trust, Karen Partington, said: “Anyone with a long-term medical condition, or who is pregnant or over 65, should contact their GP if they think they have flu, as the risk of complications in these patient groups is increased.
"The flu vaccine is the best protection against flu, and there’s still time to get it.
"Anyone in these patient groups who hasn’t yet taken up the offer of a free flu jab should contact their GP practice as soon as possible to protect themselves and their families.”
Hospital admissions and GP visits due to flu are also rising across the country, said Claire Roach, of Public Health England.
"People suffering with flu-like symptoms should catch coughs or sneezes in tissues and bin them immediately, wash their hands regularly with soap and warm water and frequently clean regularly used surfaces to stop the spread of flu. Avoid having unnecessary contact with other people if you or they have symptoms of flu,” she added.
For more advice on protecting yourself against winter illnesses visit https://www.greaterprestonccg.nhs.uk/latest-news/flu-or-norovirus-what-do-do-1375