Bird flu outbreaks among dairy cows in several states and at least one farm worker infection in Texas have raised concerns that the virus could become the next threat to humans. It's increasing.
The influenza virus, called H5N1, is highly pathogenic and can cause severe illness and death. But while the spread among cattle was unexpected, federal officials said people can only contract the virus through close contact with infected animals, not from each other. Ta.
“It's really a question of people in the environment who may come into contact with cows infected with this virus,” said Dr. Demetre Daskalakis, director of the U.S. Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases.
“The risk for most other people is very low,” he added. “At this time, there are no changes to our risk assessment, but if they do, we will respond quickly and transparently to them.”
Avian influenza is often fatal to birds, but so far no infected cows have died. The Texas patient's only symptom was conjunctivitis, or conjunctivitis, which has also been reported in infected people during other bird flu outbreaks.
The CDC and U.S. and other agencies have been tracking H5N1 for years to monitor its evolution. Federal agencies are stockpiling vaccines and drugs in case of a possible bird flu outbreak.
Rick Bright, CEO of Bright Global Health, a consulting firm focused on improving responses to public health emergencies, said: “We are probably more prepared for an influenza pandemic than for any future pathogen.'' has been completed,” he said.
Dr. Bright led influenza preparedness at the Biomedical Advanced Research and Development Authority (BARDA), a federal agency that supports research into vaccines and emergency drugs, for several years before serving as director of the agency from 2016 to 2020. .
Here's what you need to know about the H5N1 virus.
Is a human pandemic inevitable?
Among birds and animals, H5N1 avian influenza has already become a pandemic, or panzoonous disease, with infections observed on every continent except Australia. To date, this virus has not evolved to be easily transmitted from person to person, and may never be able to do so.
As its name suggests, H5N1 is primarily a problem in birds. However, it has now spread to a wide range of species, from small carrion species such as seabirds and foxes to large mammals such as bears and cows.
Human infections have occurred sporadically since 1997, when an outbreak occurred in Hong Kong. However, most patients around the world had very close contact with infected animals and generally did not transmit the virus to others.
To become adept at transmitting from person to person, H5N1 will need to find a few more mutations to change its shape. A strain isolated from an infected farm worker in Texas contains one of these mutations, but the change has previously appeared in humans, foxes and seals, with no further effects. .
Vincent Munster, a virologist at the National Institute of Allergy and Infectious Diseases who studies the mutations necessary for H5N1 to adapt to humans, said that so far, human infection has “fortunately disappeared over time.” “This is also a single interspecies infection.”
History suggests that even if the virus changes enough to start transmitting widely among people, something may have to be given up in exchange, Dr. Munster said. For example, when other influenza viruses adapt to humans, they lose much of their virulence and cause only mild symptoms.
How do we know if the virus can spread to people?
H5N1 is an influenza virus that is tracked by an extensive scientific network that tracks influenza viruses around the world.
“We're looking at it, and we've been looking at it for years,” Dr. Daskalakis said.
These surveillance networks were tracking H5N1 even before it exploded in birds and animals over the past two years. Now they are on high alert. Scientists are monitoring mutations that could make the H5N1 virus more likely to infect humans or make it more resistant to vaccines and drugs available to combat it.
The World Health Organization, CDC, and other world health organizations regularly share information and genetic sequences to monitor which influenza strains are circulating where.
In the current outbreak, the USDA is sharing the genetic sequences of infected cattle with the CDC, which analyzes the sequences to ensure that vaccines and drugs in stockpiles are still effective.
Is there a vaccine for bird flu?
yes.
BARDA contains enough vaccine components (including adjuvants, substances that increase the vaccine's strength) to produce millions of doses in a matter of weeks. Federal officials said mass production could be rapidly scaled up if needed.
The CDC already has two candidate viruses that can be used to make vaccines. As the virus changes (for example, by acquiring mutations that make it resistant to current vaccines and drugs), federal researchers may create new candidates.
Three pharmaceutical companies could be commissioned to produce avian influenza vaccines, but those vaccines would be made on the same production lines used to make seasonal influenza vaccines. David Boucher, director of infectious disease control and response at the Department of Health and Human Services, said federal officials need to consider the impact of seasonal production disruptions before embarking on large-scale manufacturing.
Not all pharmaceutical companies use egg-based methods for vaccine production, an important consideration as an outbreak of bird flu could disrupt the country's egg supply. BARDA is also considering adding mRNA to the list of technologies that can be used to produce avian influenza vaccines. (The coronavirus vaccines made by Pfizer and Moderna relied on this method.)
What about treatment?
At least four antiviral drugs are available to treat people who may contract avian influenza, including the widely available generic drug oseltamivir (sometimes sold as Tamiflu). included.
Unlike vaccines, which are stockpiled by the federal government, antiviral drugs are commercially available. Generic versions of oseltamivir are manufactured by many manufacturers around the world.
Dr. Boucher said the federal government has tens of millions of doses of oseltamivir in stockpiles. The government is in close contact with manufacturers who may quickly ramp up production of oseltamivir, as it has done during past influenza seasons.
All these preparations are being made for the worst-case scenario, but “we're not there yet,” Dr. Bucher said. “Our job here is to prepare for the worst and be prepared if it happens.”