H5N1 bird flu claims first US victim in Louisiana

H5N1 has swept through US dairy and poultry farms. Photo / AFP

A man in Louisiana has become the first person ever to die of H5N1 bird flu in the United States.

The patient, a 65-year-old with underlying health conditions, tested positive for the virus in mid-December and was sent to hospital soon after.

He is believed to have caught the disease directly from birds kept on his property, the US Centres for Disease Control (CDC) previously said.

Local health authorities in Louisiana said no further cases had been detected and there was no evidence of transmission between humans.

H5N1 has swept through US poultry farms and dairy cattle herds in a major outbreak which began last year.

Over 900 herds have now been infected across the country, according to the latest figures from the CDC.

As a result, more than 60 people have contracted the virus, the vast majority of them agricultural workers who had contact with infected animals.

Nearly all of the cases detected so far have presented with mild symptoms, including conjunctivitis and sore throat.

However, the Louisiana patient contracted a different strain of the virus, one linked directly to birds rather than the strain circulating among dairy cattle. This bird-derived strain is believed to cause more severe illness.

In neighbouring Canada, an otherwise healthy teenage girl required several months of treatment in an intensive care unit after catching what was believed to be the bird-derived strain.

Over the last 25 years, more than 940 people, largely in Asia and Egypt, have been infected with H5N1 and just under 50% of them – 464 people – have died.

It’s not yet understood why the strain circulating in dairy cattle, known as the B3.13 genotype, is causing only mild illness in humans.

Scientists say it may have something to do with the way the virus is transmitting, as most patients have contracted H5N1 through contact with milk from infected cows.

It’s thought that inhaling the virus directly into the airways could make it cause much more severe illness.

Another hypothesis is that the strain circulating in cattle is inherently less severe than that from wild birds.

Scientists recently discovered H5N1 is just one mutation away from developing the ability to transmit from one person to another, a step that would almost certainly lead to a human pandemic.

The British Government recently announced it had procured five million doses of an H5 vaccine, in case the virus does indeed start to spread between humans.