Cows are seen standing in a feedlot on June 14, 2023 in Quemado, Texas.
Brandon Bell | Getty Images
US health officials are monitoring the bird flu virus in humans and preparing to combat it, even as they stress that the risk to the general public remains low.
A strain of bird flu called H5N1 has been confirmed in dairy cows in nine US states, along with two people, amid an ongoing global outbreak among poultry and other animals. The latest case was announced Wednesday in a dairy farm worker from Michigan. The country announced on Tuesday that an Australian child was recently infected with bird flu.
The H5N1 virus has been spreading among more animal species around the world since 2020, but its discovery in American livestock earlier this year was a development that health officials did not expect. In rare cases, bird flu viruses spread to humans and can cause mild to severe symptoms that may require hospitalization.
There is currently no evidence that the H5N1 virus spreads from person to person. The Centers for Disease Control and Prevention also said the risk of infection is higher among farmworkers than among the general population.
However, the US government, along with state and local health departments, is monitoring new and emerging infections among humans and animals. Federal agencies in the United States and elsewhere have also tracked the H5N1 virus for years to monitor its evolution.
The US government has long held a stockpile of vaccines and drugs for use against a potential bird flu pandemic. Last week, it began preparing nearly 5 million doses of vaccines that are expected to be well-matched against the H5N1 virus, among other response efforts, the Department of Health and Human Services confirmed to CNBC.
Some infectious disease experts told CNBC that the US government appears generally prepared if bird flu begins to spread more widely and easily among humans, especially compared to how prepared the country is for the Covid pandemic. Experts said most of the necessary tools are already available, but the government must ensure they are deployed effectively, if necessary.
“There are a lot of pieces already in place that help us understand that we can respond to this faster,” said Dr. Andrew Pekosh, a professor at the Johns Hopkins Bloomberg School of Public Health. “But as always, it's about the efficiency of our responses, right? We know what we can do. We just have to be able to do it effectively.”
The latest human infection in a dairy worker in Michigan is not surprising, according to both experts and the government. The CDC said Wednesday that similar cases could be identified in humans because high levels of the virus have been found in raw milk from infected cows.
Millions of vaccine doses
The US government currently has two virus vaccine candidates that it believes are a good match for the H5N1 virus. These candidates are weakened versions of the virus that trigger a protective immune response against it in the body and can be used to produce vaccines.
Both candidates are already available to manufacturers, according to the CDC. The Department of Health and Human Services confirmed that the government began the process of manufacturing 4.8 million doses of these human vaccines last week in case they are needed.
Bikosh described these doses as “the first line of defense in the event of transmission from one person to another.” He said that number is enough to stop the outbreak in its early stages, which could include vaccinating farmworkers and some health care workers.
But he said much more would be needed for more than 300 million people in the United States if the virus spreads widely among people.
“Five million doesn't get us much. It's just a quick start,” Pekosh said.
US health officials said earlier this month that the government could ship more than 100 million doses of human bird flu vaccines within three to four months if needed, NBC News reported.
It is worth noting that people will need two doses of the vaccine, meaning that 100 million doses are sufficient for only 50 million people. This indicates that the United States will need approximately 600 million doses if it wants to vaccinate the entire population.
The government faces a difficult decision regarding the number of doses that must be prepared, especially since it takes a few months to prepare them.
“It's either too little or too much. For example, if you prepare too much food, a lot of food will go to waste,” said Dr. Peter Chin-Hong, an infectious disease physician at UC San Francisco Health. “That's the big dilemma now with a vaccine when you have a potential threat. It's the high cost and the high-risk aspects.”
Misinformation and post-Covid vaccine hesitancy make this decision more difficult, he said. But Chen Hong said he believes “you can never invest too much” in preparing for potential pandemics, especially at a time when climate change, population growth and other factors make them more likely.
The Food and Drug Administration will need to approve bird flu vaccines before they can be rolled out. But Piekosh said it would likely be a “quick action” since the FDA is used to clearing seasonal flu vaccines, which are made using the same manufacturing process as bird flu vaccines.
Potential mRNA shots
US health officials are also in talks with messenger RNA (mRNA) vaccine makers about potential bird flu vaccines for humans. Few details about those negotiations have been shared, but the Department of Health and Human Services said a final announcement is expected soon.
Unlike traditional flu vaccines, mRNA works by teaching cells to produce a harmless piece of the virus, triggering an immune response against certain diseases. It's the same technology for both Pfizer And Moderna Which they used in their Covid vaccines.
Chen Hong said mRNA vaccines could be updated more quickly to match currently circulating bird flu strains. But those vaccines have their own challenges, such as the need to store them at extremely cold temperatures, he said.
In a statement to CNBC, Moderna confirmed that it is participating in negotiations with the government regarding its experimental pandemic influenza vaccine, mRNA-1018. It targets the exact strain of the virus responsible for the outbreak in dairy cows.
The biotech company began testing that shot in an early- to mid-stage trial last summer.
Pfizer declined to confirm negotiations with the government. The company said it continues to monitor the spread of the H5N1 virus and study its mRNA-based pandemic influenza vaccine candidates in an early trial.
Virus monitoring and treatment
CDC and its partners, including state and local health departments, use multiple surveillance systems to monitor seasonal influenza and other diseases. They also have specialized methods for detecting and monitoring new influenza viruses.
Seasonal influenza spreads mostly among humans and peaks during the year, while avian influenza spreads mostly among wild birds and other animals.
The Centers for Disease Control and Prevention said it is looking for the spread of the H5N1 virus to or among people in areas where the virus has been identified in animals or humans. So far, the agency has found “no indications of unusual influenza activity in humans,” including the H5N1 virus, according to an update on the agency's website from last week.
CDC also conducts ongoing analyzes of seasonal and new influenza viruses to identify genetic changes that may allow them to cause more serious infections in humans, spread more easily between people or become less susceptible to vaccines and drugs.
Although there is robust testing at the federal, state and local levels, it is just as difficult for the average person to self-test and be diagnosed with bird flu as it is for COVID. This is “the big hurdle, especially among the residents who are being affected now,” Chen Hong said.
Chen Hong points to farmworkers, a large percentage of whom are immigrants, who may struggle to navigate the American health system due to language barriers and access to health care.
If people become infected with the virus, there are a few FDA-approved antiviral medications for seasonal influenza that can be used to treat bird flu. This includes Tamiflu, an oral prescription drug that must be taken within 48 hours of the onset of symptoms.
A Texas dairy farm worker who was diagnosed with bird flu in March was treated with an antiviral drug and recovered, according to a CDC report.
But Piekosh said antiviral drugs in the country's stockpile would likely not be enough for the vast majority of the population, so manufacturers may be asked to increase supply.
The average person can protect themselves from bird flu by avoiding any live or dead animals that may be infected, such as livestock or chickens, according to Francesca Torriani, a clinical professor of medicine at the University of California, San Diego.
People who need to come into contact with these animals should wear an appropriate mask and eye protection and wash their hands afterward.
Torriani added that pasteurized milk and cheese are likely safer to consume than raw dairy products because the pasteurization process kills harmful bacteria.
