Two poultry farmers have tested positive for bird flu after they came into contact with infected birds in England, the UK Health Security Agency (UKHSA) said on Tuesday.

The cases were found in the workers, both of whom had no symptoms, after they had come into contact with contaminated birds.

Humans that contract bird flu (also known as avian influenza) may suffer a serious infection and can develop symptoms after merely inhaling infected air from a farm.

One of the affected employees in this week’s case was, it is thought, almost certainly contaminated after inhaling farm-related contaminants. This is according to the timing of exposures and test results.

According to the Department for Environment, Food & Rural Affairs and Animal and Plant Health Agency, there have been 183 confirmed cases of highly pathogenic avian influenza (HPAI) H5N1 since October last year; 153 of these were in England, 21 in Scotland, eight in Wales, and one in Northern Ireland.

So what is bird flu and what should you do if you see an affected bird?

What is bird flu and how is it transmitted?

The Department for Environment, Food and Rural Affairs (Defra) says wild birds migrating to the UK from mainland Europe during the winter months can carry the disease. This can lead to cases in poultry and other captive birds.

Birds can be infected with the avian influenza virus through contact with infected birds or waste products. Wild birds including waterfowl (swans, ducks, geese) can carry and transmit the virus without showing evidence of disease, according to Paul Walton, head of habitats and species at the Royal Society for the Protection of Birds (RSPB) Scotland.

How do you spot bird flu?

There are two types of avian influenza, with highly pathogenic avian influenza (HPAI) being the more serious type. It is often fatal in birds.

Some of the clinical signs of HPAI in birds include a sudden and rapid increase in the number of birds found dead; several birds affected in the same shed or air space; a swollen head; closed and excessively watery eyes; head and body tremoring; drooping of the wings and/or dragging of legs; twisting of the head and neck; and swelling and blue discolouration of comb and wattles.

Other signs include haemorrhages on shanks of the legs and under the skin of the neck; loss of appetite or marked decrease in feed consumption; a sudden increase or decrease in water consumption; respiratory distress; sneezing; a noticeable increase in body temperature; discoloured or loose, watery droppings; and cessation or a marked reduction in egg production.

What can the Government do about bird flu?

The RSPB is calling for UK governments “to develop a response plan urgently”.

The charity says: “We want to see co-ordinated surveillance and testing of wild and domestic birds, carcasses to be safely disposed of, and vulnerable bird populations protected. We also want measures put in place to stop the unnecessary disturbance of wild birds affected by the virus.

“In the longer term, we want much higher importance being given to prioritising and funding seabird conservation. This would help make our seabird populations more resilient to these diseases and the other challenges they face.”

What is the risk to the public from bird flu?

The risk to human health from the virus is very low. Food standards bodies advise that avian influenzas pose a very low food-safety risk for UK consumers, according to Defra.

People are advised not to touch or pick up any dead or sick birds that they find and instead report them to the relevant helpline.

Defra says there is no impact on the consumption of properly cooked poultry products, including eggs.

Is it still okay to feed birds in your garden amid bird flu?

The RSPB says everyone should take care to maintain good hygiene when feeding garden birds. It also recommends “regularly cleaning feeders outside with mild disinfectant, removing old bird food, spacing out feeders as much as possible, and washing your hands”.

UK chief veterinary officer Christine Middlemiss said people who keep chickens and want to feed wild birds need to make sure everything is kept “scrupulously clean” and “absolutely separate” to avoid infecting their own flocks.

What should you do if you see a sick or injured bird?

The RSPB says if people find any dead waterfowl, any gulls or birds of prey, or five or more of any other species in one place, they should report them to the Defra helpline on 03459 335577 or in Northern Ireland to the Department of Agriculture, Environment and Rural Affairs (Daera) on 0300 200 7840.

The RSPB also advises that people who live in bird-flu areas should keep their dogs on a lead, as the virus can be passed to pets.