Scientists tracking the spread of bird flu are increasingly concerned that gaps in surveillance could cause them to fall behind a new pandemic, according to Reuters interviews with more than a dozen scientists. eminent specialists in the disease.
Many have been monitoring the new H5N1 avian flu subtype in migratory birds since 2020. But the virus’s spread to 129 dairy herds in 12 U.S. states signals a shift that could bring the virus closer to human-to-human transmission. Infections have also been seen in other mammals, from alpacas to domestic cats.
“It almost feels like a pandemic happening in slow motion,” said Scott Hensley, a professor of microbiology at the University of Pennsylvania. “Right now, the threat is pretty low … but that could change in the blink of an eye.
The earlier the warning of a human outbreak, the more steps global health authorities can take to protect the population by initiating vaccine development, widespread testing and containment measures.
Federal oversight of dairy cows in the United States is currently limited to testing herds before they cross state lines. State testing efforts are inconsistent, while testing of people exposed to sick cattle is low, public health officials and pandemic flu experts told Reuters.
“You need to know which farms are positive, how many cows are positive, how much the virus is spreading, how long these cows stay infectious, what the exact transmission route is,” said Dutch virologist Ron Fouchier, of the Erasmus Medical Center Rotterdam.
Dr. Jeanne Marrazzo, director of the US National Institute of Allergy and Infectious Diseases, said surveillance of humans was “very, very limited.”
Ms. Marrazzo described the U.S. Centers for Disease Control and Preventions’ human influenza surveillance network as “a passive reporting and reporting mechanism.” The U.S. Department of Agriculture is more proactive about testing cows, but it does not make affected farms public, she said.
Several experts said differences in approach between animal and human health agencies could hamper a faster response.
“If you were designing the system from scratch, you would have only one agency,” said Gigi Gronvall, a biosecurity expert at the Johns Hopkins Center for Health Security. “This is not the only example of environmental or animal problems leading to human problems.
A USDA spokesperson said the agency is working “around the clock” with the CDC and other partners as part of a whole-of-government response, adding that ongoing research shows that “supply America’s Food Standard remains safe, that sick cows generally recover within a few weeks, and that the risk to human health remains low.”
In a statement, the CDC said “the USDA and local and state health departments across the country have been preparing for the emergence of a new influenza virus for nearly two decades and continuously monitoring for the slightest changes in the virus.
A NOTE OF CAUTION
Some pandemics, including COVID-19, occur without us noticing. During the last flu pandemic, caused by the H1N1 virus in 2009, the virus and its predecessors had already been spreading among animals for several years, Hensley said, but increased surveillance would have helped health authorities prepare.
Since late March, three people in the United States have tested positive for the H5N1 bird flu virus after coming into contact with cows and have had mild symptoms. One person in Mexico was infected with a separate H5 strain that had not previously been seen in humans and had not been exposed to animals. Other cases have been reported in India, China and Australia, caused by different strains.
The World Health Organization considers the risk to humans from the H5N1 virus to be low, as there is no evidence of transmission to humans. Some tools are available in case of change, including limited quantities of the existing H5N1 vaccine and antiviral drugs such as Tamiflu.
There are mechanisms to launch larger-scale production of tests, treatments and vaccines, if necessary, said Wenqing Zhang, head of the U.N. agency’s flu fight.
Other experts said there was enough concern to start preparing for possible spread to humans, although the triggers for action differ depending on the role played in the response, Richard Hatchett said , executive director of the Coalition for Epidemic Preparedness Innovations (CEPI). His organization acted early in funding COVID vaccine development and is currently in talks with research partners about H5N1.
CEPI aims to create a library of vaccine prototypes for pathogens with pandemic potential. This would help drugmakers launch large-scale production and distribute vaccines if needed within 100 days of an outbreak.
Some countries are taking measures to protect the population against H5N1. The United States and Europe are saving doses of pre-pandemic flu vaccine that could be used for high-risk groups, including agricultural or laboratory workers. Finland is expected to be the first country to vaccinate fur farm and poultry workers, as well as animal health workers.
Expanding access to vaccines is also complex, said WHO’s Zhang. Manufacturers of potential pandemic flu vaccines produce seasonal flu vaccines and cannot produce both at the same time.
Since most flu vaccines are made from viruses grown in eggs, pandemic vaccines could take up to six months to produce. The U.S. is in talks with Moderna to use its faster mRNA technology for pandemic flu vaccines.
Experts all acknowledged the need to strike a balance between acting quickly to avoid a threat and overreacting.
“We want to urge caution,” said Wendy Barclay, a virologist at University College London who researches avian flu for the UK Health Security Agency, “without saying that the end of the world is imminent.” (Reporting by Jennifer Rigby and Julie Steenhuysen; Writing by Michele Gershberg and Bill Berkrot)
