What is bird flu, and should you be worried about it?

The Guardian

10-03-2025

Bird flu has been spreading in North America since late 2021, but recently the situation has taken some concerning turns.
In January, the first person in the US died from bird flu. In February, two more people were hospitalized, and officials detected two new spillovers into cows, indicating the virus is here to stay among livestock and farm workers. The price of eggs has also skyrocketed as bird flu moves through egg-laying chickens.
'The past couple of weeks, it's all been new plot twists in the H5N1 story,' said Meghan Davis, an associate professor of environmental health at the Johns Hopkins Bloomberg School of Public Health.
People who work closely with wild and domesticated animals should take precautions, such as washing their hands, wearing a face mask while handling sick or dead poultry and cleaning their litter, and monitoring symptoms after contact with animals.
But most people should feel 'alert, not alarmed', Davis said.
'The overall risk to the average person remains low,' said Boghuma Titanji, an infectious diseases physician and assistant professor of medicine at Emory University.
'But have an awareness, because that could potentially change – because the outbreak is not quite contained.'
Bird flu is influenza that usually spreads in birds – but it can also be transmitted to other animals and people.
There are several types of bird flu, but right now the H5N1 strain is a highly pathogenic avian influenza spreading widely in wild and domestic species, and spilling over into people.
Bird flu usually causes respiratory symptoms and sometimes stomach upset.
Patients usually have typical flu symptoms: cough, fever, fatigue, body aches and headaches. Some patients have runny or stuffy noses and sore throats, and some people experience diarrhea, nausea or vomiting.
More severe illness includes difficulty breathing or shortness of breath, seizures and what the US Centers for Disease Control and Prevention (CDC) calls 'altered consciousness' – all signs that a patient should go to the hospital.
Very red or irritated eyes (known as conjunctivitis or 'pink eye') have also been a common symptom in this outbreak, and are not a typical flu symptom.
Since 2003, there have been more than 950 reported cases of H5N1 globally, and 49% of patients have died.
In the US outbreak, the mortality rate has been much lower so far. There have been 70 confirmed cases, and several more probable cases, in the past year. One person has died, and three others have been hospitalized.
It's possible the mortality rate is lower because the cases detected in this outbreak have been less severe. But the mortality rate is still significantly high in cases that are bad enough to need hospital care, said Davis.
In countries with poor access to healthcare, the mortality rate may be higher because sick patients aren't able to get care that could save their lives, she said.
'The virus can be really nasty for some people,' said Megan Ranney, an emergency physician and dean of the Yale School of Public Health.
We don't know yet what puts someone at risk of getting really sick, Ranney said.
Flu viruses mutate and evolve quickly. If bird flu begins spreading between humans, there could be changes in how it sickens people, she added. 'There's really no way for me to say, if it becomes a pandemic, that we're going to have the same case fatality ratio that we're seeing right now.'
Bird flu spreads through contact with animals and unpasteurized animal products. That means the people who are most at risk are those who care for chickens and dairy cattle, those who come into contact with wild birds and animals, and anyone drinking raw milk or eating undercooked meat.
There have also been two US cases, in California and Missouri, where patients got sick with H5N1 with no known contact with animals or raw food.
There has been no documented transmission between humans.
However, details about the outbreak have been scarce in the past month especially, starting with a communications blackout at health agencies, so it's not clear if new patterns of transmission have emerged.
'We're missing opportunities to learn more about this virus and the risk that it poses to people and our economy,' said Jennifer Nuzzo, professor of epidemiology and director of the Pandemic Center at Brown University School of Public Health. 'But also, we're missing the opportunity to possibly discover something that would make us worry less about the virus.'
Flu antivirals like Tamiflu seem to work against bird flu by reducing the severity of illness and possibly keeping patients from transmitting it to others.
But Tamiflu needs to be given soon after illness starts. And scientists recently identified a strain that could demonstrate some resistance to antivirals.
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'We need more therapeutics,' said Nuzzo.
Yes, there are bird flu vaccines for people and for animals. But we don't use them yet.
Some of the shots for people have been licensed for use in the US, while others are still awaiting approval. The US government has stockpiled 4.8m doses of H5N1 vaccines.
But none of them are available to the public. The reasons why are complicated: there have been few hospitalizations and deaths in the US, there isn't evidence of person-to-person transmission, and officials worry about hesitation over a new vaccine, Nirav Shah, principal deputy director of the CDC, has told the Guardian.
Experts say the vaccine should be made available to farm workers, veterinarians and other people at risk. 'This is a recurring occupational hazard,' Nuzzo said.
There are also vaccines for poultry, and scientists are working on a cow vaccine as well. But none of these have been given to animals yet.
'You should get the seasonal flu vaccine to protect you from seasonal flu,' Davis said. Another reason is that in rare cases when someone catches H5N1, they might catch the seasonal flu at the same time – and the two variants could mix together in a process called reassortment.
This could cause H5N1 to become more easily transmissible or cause more severe disease, suggested Davis. 'Brand-new viruses that can transmit easily are the ones that tend to cause epidemics or pandemics.'
Fewer cases of seasonal flu takes pressure off the healthcare system during flu season, and makes it easier for doctors and health departments to identify rare infections like H5N1.
Any hopes that the current outbreak would simply pass through 'have been dashed', Nuzzo said.
'We have to be looking ahead to what would happen if this virus began spreading more easily between people,' Nuzzo has said. 'If it could spread easily between people, we would be in a pandemic, and it would be around the globe in a matter of weeks.'
Experts expect another flu pandemic at some point. It might not be H5N1 – it might be a combination of H5N1 and a different flu variant, or a different type altogether.
That means it's important to prepare vaccines, treatments and tests, and to strengthen healthcare systems.
Yes. Your doctor can order an H5N1 test for you at commercial laboratories.
It's important to let your doctor know why you think you might have bird flu – for instance, if you work closely with animals or consume raw milk, meat or eggs.
'It will help the health authorities to get things in the queue much faster for further testing,' Davis said.
Raw milk can contain enormous quantities of virus. While no cases have been reported yet in humans from drinking raw milk, it has sickened and killed mammals such as cats – so officials strongly recommend against it for people, as well. Pasteurization (boiling milk for a certain amount of time) kills the virus and makes milk safe to drink. Eggs and meat should be cooked fully to kill all pathogens, including bird flu, according to the US Food and Drug Administration (FDA).
Davis recommended 'good hygiene practices writ large in the kitchen,' such as washing your hands after handling raw eggs or meat.
It's illegal for sick animals to enter the food chain, but US officials have detected bird flu in meat from dairy cows intended for slaughter. It's important to cook meat to an internal temperature of at least 145F/63C.
'There are many, many, many different pathogens that you can get exposed to from these sources,' Davis said, such as campylobacter, cryptosporidium, E coli, listeria and salmonella.