With the country almost completely returning to normality after years of quarantine and isolation measures, the Covid pandemic increasingly seems like a distant memory for many.
But infectious disease experts are much less forgetful and have remained vigilant since the new coronavirus was first identified in 2019, continually looking for signs of mutations or other emerging threats.
Now they believe they have found one in influenza A subtype H5N1, known as “bird flu,” which has sickened at least 66 people in 10 states. These cases were caused by people coming into contact with infected birds and livestock or by drinking unpasteurized milk.
There has been no person-to-person transmission.
However, with each new infection between species, there is an increasing risk that the virus will mutate to better infect humans.
Dr Conor Meehan, a professor at Nottingham Trent University, studies how bacteria spread and evolve, focusing on the genetic makeup of microbial communities.
He saying: ‘Compared to just two cases in the Americas in the previous two years, this is a fairly large increase. Add to that a 30 percent mortality rate from human infections, and bird flu is quickly moving up the priority list of public health officials.’
This week, the United States reported its first serious human case of H5N1 in Louisiana and California, where 36 of the country’s most common flu cases have been diagnosed, declaring a state of emergency over the virus just hours later.
At least 66 people have been infected with bird flu. Cases in California have surpassed 35, prompting a statewide emergency declaration.
H5N1 bird flu does not appear to spread from person to person, Dr. Meehan said, “which greatly reduces its likelihood of causing a pandemic in humans…in its current form, H5N1 cannot spread easily between humans “.
However, he added, “a recent study showed that a single mutation in the flu genome could make H5N1 suitable for spreading from person to person, potentially triggering a pandemic.”
Cases of bird flu in humans have generally been relatively mild, manifesting primarily as conjunctivitis (conjunctivitis), cough or difficulty breathing, sore throat, muscle or body aches, diarrhea, and vomiting.
But last week, a Louisiana patient became the first to be hospitalized with the virus. Researchers said they likely contracted the disease after handling sick and dead birds in a poultry flock.
No further details have been revealed about their symptoms, except that they are “seriously ill” with bird flu.
The CDC has not changed its overall assessment that the risk of bird flu to the public is low.
However, H5N1 has been shown to have the ability to mutate rapidly and spread among mammals.
A Michigan patient’s virus had genetic segments closely related to those in dairy cows, but there were no significant changes that improved its ability to spread among humans.
Despite that, experts noted a mutation in that patient associated with a better ability to infect and spread in mammals and greater virus replication in animals.
So while the risk of human-to-human transmission remains low, the risk of more people getting sick as it spreads between animals is increasing.
Human cases of bird flu have been due to exposure to infected cattle and poultry. Risk of human-to-human transmission remains low
Scientists at the Scripps Research Institute revealed earlier this month that only a genetic mutation in the strain of bird flu virus spread in dairy cows would allow it to attach to human cells.
The researchers altered one of H5N1’s proteins called hemagglutinin, which is what attaches to human cells and allows the virus to infect.
The team generated viral proteins from virus genes taken from a person in Texas who developed bird flu after contact with an infected cow.
They then engineered different mutations into hemagglutinin and discovered that just a small change in the genetic makeup of H5N1 allowed it to go from infecting bird cells to infecting human cells in the upper respiratory tract.
Dr. Ian Wilson, a computational biologist at Scripps and co-author of the study, said, “This was surprising. It was this single mutation that was enough to change the specificity of the receptor.”
Governments are already showing signs of preparing for this growing threat. The UK has purchased 5 million doses of the H5 vaccine which can protect against bird flu.
In June this year, Finland became the first country to offer bird flu vaccines to humans, giving two shots to 10,000 people. The vaccines were administered to workers who have been exposed to animals.
This map shows cases of the virus detected in wild mammals, such as red foxes and seals.
And the U.S. government purchased vaccines and commissioned Moderna to create an mRNA vaccine against bird flu.
Dr Meehan said: “Even without the potential ability to spread between humans, bird flu is likely to further impact animal health in 2025.
«By understanding and preventing diseases in our environment and in the animals around us, we can better prepare for and combat diseases that reach humans. Likewise, by studying and combating infectious diseases in humans, we can protect the health of our animals as well as the environment.’