Lancashire's director of public health said the risk to people remains "very low", but he has warned against handling sick or dead birds to avoid spreading the virus.
The exact location of the confirmed cases has not been made public, but the Department for the Environment, Food and Rural Affairs (Defra) said it has been detected in Lancashire's wild bird populations.
Dr Sakthi Karunanithi, director of public health for Lancashire County Council, said: "I want to reassure residents that the risk to public health from avian flu is very low.
"However, it is important that people do not pick up any sick or dead birds to avoid spreading the virus, which can affect humans in rare cases.
"If you do find any dead swans, geese or ducks or other dead wild birds while out and about, please report them to the Defra helpline on 03459 33 55 77.
"I would also urge bird keepers to be vigilant for any signs of disease and report any suspected cases to their nearest Animal and Plant Health Agency (APHA office)."
The warning follows several confirmed cases of avian influenza in wild birds across Britain. The avian influenza circulates naturally in wild birds and when they migrate to the UK from mainland Europe over the winter, they can spread the disease to poultry and other captive birds, says Defra.
Mark McGivern, consultant in health protection in the North West at the UK Health Security Agency, echoed Dr Sakthi's advice.
"The risk to public health from the virus is very low," he said, "however it is important that people don’t pick up sick or dead birds.
"As a precaution, anyone who was in contact with the droppings or birds in an area where the infection has been confirmed, is undergoing close monitoring and are assessed to determine whether a course of antiviral medication is also required.
"I would also urge bird keepers to be vigilant for any signs of disease, to report any suspicions of disease to their nearest Animal and Plant Health Agency (APHA) office and to ensure they are maintaining good biosecurity on their premises."
People who find dead swans, geese or ducks or other dead wild birds, such as gulls or birds of prey, should report them to the Defra helpline on 03459 33 55 77.
Advice for bird keepers in Lancashire
It is now a legal requirement for all bird keepers in Lancashire and across Great Britain to follow strict biosecurity measures to help protect their flocks, says Defra.
Keepers with more than 500 birds will need to restrict access for non-essential people on their sites, workers will need to change clothing and footwear before entering bird enclosures and site vehicles will need to be cleaned and disinfected regularly to limit the risk of the disease spreading.
Backyard owners with smaller numbers of poultry including chickens, ducks and geese must also take steps to limit the risk of the disease spreading to their animals.