- Avian flu is increasingly worrying public health experts.
- The H5N1 avian influenza virus is changing, becoming more similar to humans and giving it more opportunities to adapt.
- An avian flu pandemic isn't inevitable, but it's possible. Here's why you should know what's happening.
Bird flu is raging, leaving many infectious disease experts more concerned than ever.
The H5N1 avian influenza virus has killed tens of millions of birds and more than 40,000 sea lions and seals around the world, creating an animal pandemic.
Still, the CDC says the risk to humans is low: Most people are unlikely to become infected with H5N1 avian flu at this time.
Since the virus suddenly spread through cattle herds, only three people in the United States have tested positive for the virus, all of whom had direct contact with infected cattle.
But infectious disease experts are increasingly concerned that the H5N1 virus could become persistent in humans and begin to spread among them. That's not inevitable, but some recent developments suggest it's a growing threat.
“There's a lot going on,” Dr. Monica Gandhi, professor of medicine and vice chair of the department of HIV, infectious diseases and global medicine at the University of California, San Francisco, told Business Insider. “It's getting more and more worrying.”
There's no need to panic, but you should be aware of what's going on. This virus is a strong candidate to become the next pandemic, and four events have happened in the past month that have experts worried.
Here's what you need to know:
Child hospitalized with bird flu in Australia
The World Health Organization said Friday that a two-year-old child in March became Australia's first case of the H5N1 virus.
After returning from a trip to Kolkata, India, the child developed symptoms including loss of appetite, fever, cough, vomiting and irritability and was hospitalized for two and a half weeks, including in intensive care, according to the WHO.
The growing number of human cases around the world has epidemiologists like Christopher Dye growing increasingly concerned.
“There's a huge amount of virus out there right now, and clearly the virus is changing, producing new and unexpected phenomena,” Dai, a professor and senior research fellow at the University of Oxford, told BI.
He is co-author of a recent study in the medical journal BMJ which argues that the risk of a large-scale human outbreak is “large, real and imminent”.
“Influenza has been a concern for decades, and this particular influenza has been a concern for at least 20 years,” Dye said, “but now I think the level of concern is greater than it's ever been.”
Rats could bring bird flu into homes
A total of 47 mice in New Mexico have tested positive for the H5N1 virus, the U.S. Department of Agriculture announced Tuesday.
“Rats are everywhere,” Gandhi said, “around other animals and often around people. It's a bit worrying.”
The samples were taken from infected rats in early May, and scientists suspect that some of the rats and house cats may have contracted the virus by drinking raw milk from infected cows, according to The Telegraph. (Public health experts strongly advise against drinking unpasteurized “raw” milk.)
“This brings the virus closer to human habitation,” Rick Bright, a former director of the Biomedical Advanced Research and Development Agency, told The Telegraph. “This is out of control,” he added.
New animal populations and new exposure to humans provide opportunities for the virus to mutate and adapt.
One mutation suggests the virus is beginning to adapt.
When the CDC analyzed virus samples taken from the second US farm worker infected, they found a mutation in the virus's replication mechanism (the way the virus enters host cells and makes copies of itself).
The CDC said in a May statement that this is a change “associated with the virus's adaptation to its mammalian host.” The statement also said that studies in mice have shown that this type of genetic mutation in the virus is associated with more severe disease and enhanced viral replication.
But it still can't be called a human virus.
Apart from this one change, H5N1 mainly “has the characteristics of avian viruses and not of human viruses,” Richard Webby, a virologist at St. Jude Hospital and director of the WHO Collaborating Centre for the Study of Animal and Avian Influenza Ecology, told BI.
This means the virus is better suited to breeding and spreading among birds, but not humans.
Still, things could change.
Coughing was an issue in the latest US cases
The first two farmworkers in the United States to test positive for H5N1 had conjunctivitis, but a third case reported in Michigan in May caused symptoms of cough and sore throat.
This means H5N1 was present in the worker's respiratory system, a much scarier place to find a dangerous virus than the human eye.
First, the virus spreads more easily through coughing and sneezing than through sharing fluids that have gotten into the eyes.
The good news is that, as far as scientists know, H5N1 hasn't yet adapted to humans to the point where it can be transmitted between humans, and the CDC reports that there's no evidence that coughing farmworkers can spread the virus to others.
But that doesn't mean H5N1 can't mutate and spread from person to person, which leads to the second unfortunate reality of this respiratory infection in farmworkers.
Compared to the human eye, the human lung is a favorable site for avian viruses to infect mammals, says Webby, because there the virus is exposed to more of the cellular receptors that mammalian viruses bind to, giving H5N1 more opportunity to mutate and start latching onto those receptors, making it better adapted to infecting and spreading to humans.
Many experts worry that the USDA and CDC are not monitoring cows and farm workers closely enough and are therefore missing troubling developments. It's possible that the mutation was discovered early and other human cases go undetected.
“We believe there is an alarming threat here, and that's why we have monitoring systems in place to ensure we can spot anything like this as soon as it happens,” Dai said.
Vaccine in development
The good news is that bird flu is not COVID-19: Scientists have been tracking this virus and its entire family tree for decades, watching for signs of a growing threat to humanity.
As a result, the key components of the vaccine are already ready, and the United States has begun manufacturing millions of vaccines using “candidate vaccine viruses” (weakened versions of influenza viruses) developed by the CDC.
Candidate vaccines will not necessarily be an exact match for the H5N1 strain, and using eggs in the vaccine could pose production obstacles if avian flu is rampant among chickens, but they could provide some immunity if it infects humans.
Moreover, scientists are currently preparing proven mRNA vaccine technology: vaccines using mRNA, the first of which was approved for use with COVID-19, are more flexible and quicker to develop than traditional vaccines, and do not require eggs.
Researchers at the University of Pennsylvania have already developed an experimental mRNA vaccine against H5N1. It has been tested in mice and ferrets.
If H5N1 becomes a problem in humans, the vaccine could be provided in flu shots people get later this year.
Avian flu, on the other hand, is an imminent threat that requires constant attention.
“As far as I can see, this situation isn't going to get resolved anytime soon,” Dye said.
