The initial recorded death from avian influenza in the United States has been documented after authorities verified on Monday that an individual in Louisiana, who had been admitted to the hospital with serious respiratory symptoms, passed away.

Aged over 65 with pre-existing medical conditions, the individual had interacted with diseased and deceased birds within a domestic flock, as noted by health officials.

No other details were revealed.  

Moreover, an examination of the genetic makeup of the individual’s infection indicated that the avian flu virus had undergone mutations during its time within the person’s system, potentially leading to a more intense manifestation of the illness.

Since March, 66 confirmed bird flu infections have been reported in the US, but previous illnesses have been mild and most have been detected among farmworkers exposed to sick poultry or dairy cows. 

In two cases – an adult in Missouri and a child in California – health officials have not determined how they contract the virus.

Many experts put H5N1 at the top of their lists of pandemic threats, due to how widespread it is among animals and how rapidly it appears to be mutating. 

The death in Louisiana marks the first human case in the US linked to exposure to backyard birds, according to the Centers for Disease Control and Prevention.

Louisiana officials say they are not aware of any other cases in the state, and US officials have said they do not have any evidence the virus is spreading from person to person.

The H5N1 bird flu has been spreading widely among wild birds, poultry, cows and other animals, however. 

And its growing presence in the environment increases the chances people will be exposed, and potentially catch it, officials have said.

Officials continue to urge people who have contact with sick or dead birds to take precautions, including wearing respiratory and eye protection and gloves when handling poultry. 

Infectious disease experts are also alarmed over the figures, warning the scale of cases and every infection outside of birds raises the risk of the virus gaining mutations, allowing it to spread between people.

Dr Marc Johnson, a virologist at the University of Missouri, recently said on X: ‘This virus might not go pandemic, but it is really trying hard, and it sure is getting a lot of opportunities.’

Overall, figures show since the virus was detected in the US in January 2022, more than 12,000 wild and domestic flocks have been infected.

After the virus spread to cows this year, it was diagnosed in 866 herds across 16 states – with the majority in California and Colorado.

And 66 cases have now been detected in humans across ten states this year, the most cases reported in the US in at least two decades. Before the current outbreak, the last human case of bird flu was in 1997.

The patients almost all had direct contact with either infected birds or cattle, and only suffered mild symptoms – such as conjunctivitis, or pink eye.

However, the tide has started to shift to those who don’t work with birds or cattle.

In September, a patient in Missouri became the first to be infected without any direct exposure to infected animals. It’s unclear how they became ill. 

A teenager in California who was not exposed to infected cattle was sickened last month. 

And the disease may be evolving to become more dangerous. A strain linked to wild birds has caused severe disease in humans, including a patient in Louisiana and a teenager in Canada- who was hospitalized for at least three weeks and needed help to breathe.

There is no evidence any of the patients spread the disease to other patients.

However, the virus has been detected in unpasteurized or ‘raw’ milks, leading the United States Department of Agriculture (USDA) to announce that all companies handling raw milk will be required to share samples for testing upon request. 

Many experts, including officials at the World Health Organization, have criticized the US response to the outbreak.

Experts have described it as a pandemic ‘unfolding in slow motion.’ Until last month, nearly all testing of cattle and of people exposed to infected cows were voluntary. 

Even now, mandatory testing is limited only to cattle moving between state lines.  

Cases have also been sporadically recorded in pigs, which has concerned researchers because these animals can catch both human and bird strains of flu – and could be ‘mixing vessels’ for a new strain of bird flu virus.

And infections have been recorded among 419 non-bird wild animals in the US since May 2022, including red foxes, skunks, seals and raccoons.

Experts warned these animals may pick up the virus after eating from carcasses of birds that had died from the bird flu.

Wastewater surveillance for the virus has also picked up traces in 60 of the more than 250 sites monitored across the US. 

In California and Iowa, more than 80 percent of samples have tested positive. 

The US already has a stockpile of about 20million bird flu vaccines in its national stockpile, officials say, which are ‘well matched’ to the H5N1 virus. 

It also has the capacity to quickly make 100million more if necessary. However, the Biden administration said earlier this month that it has no plans to authorize a vaccine.

There are also supplies of antivirals such as oseltamivir (Tamiflu) – which used to treat the latest US bird flu patient in Louisiana – available.

Still ongoing, is work to develop a bird flu vaccine for poultry and tests showing that human antivirals would work just as well on sick cows.