Topline
There has been a global outbreak of H5N1 bird flu since 2020, but recent outbreaks among cattle in several U.S. states and also a huge breakout among sea mammals has experts concerned the virus may mutate and eventually spread to humans, where it has proven deadly—though still very rare.
Key Facts
The global H5N1 bird flu outbreak began in 2020 after a reemergence in birds in Europe and led to the deaths of millions of birds, but it’s evolved and has increasingly been infecting mammals (on land and sea), which means it could possibly spread to humans, according Jeremy Farrar, chief scientist for the World Health Organization.
As of Tuesday, more than 90 million poultry (primarily chickens) in 48 states have been euthanized because of bird flu since 2022, and 33 dairy cow herds across eight states have tested positive, according to data from the Centers for Disease Control and Prevention (unlike chickens, cows appear to recover from the virus).
The Department of Agriculture first detected bird flu in dairy cows in March, and it believes the cows fell ill after coming into contact with infected birds, though it confirmed in an update from last week that cow-to-cow transmission through infected unpasteurized milk may also be a factor.
Can Bird Flu Spread Between Humans?
Bird flu doesn’t “transmit easily from person-to-person,” according to the World Health Organization. Bird flu rarely affects humans, and most previous cases came from close contact with infected poultry, according to the CDC. Because human-to-human spread of bird flu poses “pandemic potential,” each human case is investigated to rule out this type of infection. Though none have been confirmed, there are a few global cases—none in the U.S.—where human-to-human transmission of bird flu was thought to be “probable,” including in China, Thailand, Indonesia and Pakistan.
Is Bird Flu Fatal To Humans?
It is very deadly. Between January 2003 and March 28, 2024 there have been 888 human cases of bird flu infection in humans, according to a report by the World Health Organization. Of those 888 cases, 463 (52%) died. To date, only two people in the U.S. have contracted H5N1 bird flu, and they both were infected after coming into contact with sick animals. The most recent case was a dairy worker in Texas who became ill in March after interacting with sick dairy cows, though he only experienced pink eye. The first incident happened in 2022 when a person in Colorado contracted the disease from infected poultry, and fully recovered.
Is It Safe To Drink Milk Infected With Bird Flu?
Raw, unpasteurized milk is unsafe to drink, but pasteurized milk is fine, according to the FDA. Bird flu has been detected in both unpasteurized and pasteurized milk, but the FDA recommends manufacturers against making and selling unpasteurized milk since there’s a possibility consuming it may cause bird flu infection. However, the virus remnants in pasteurized milk have been deactivated by the heat during the pasteurization process, so this type of milk is still believed safe to consume.
Is It Safe To Consume Meat Infected With Bird Flu?
The CDC warns against eating raw meat or eggs infected with bird flu because of the possibility of transmission. However, no human has ever been infected with bird flu from eating properly prepared and cooked meat, according to the agency. The possibility of infected meat entering the food supply is “extremely low” due to rigorous inspection, so properly handled and cooked meat is safe to eat, according to the USDA. To know when meat is properly cooked, whole beef cuts must be cooked to an internal temperature of 145 degrees Fahrenheit, ground meat must be 160 degrees and poultry must be cooked to 165 degrees. Rare and medium rare steaks fall below this temperature. Properly cooked eggs with an internal temperature of 165 degrees fahrenheit kills bacteria and viruses including bird flu, according to the CDC. “It doesn’t matter if they may or may not have [avian] influenza… runny eggs and rare pieces of meat” are never recommended, Francisco Diez-Gonzalez, director and professor for the Center for Food Safety at the University of Georgia, told Forbes. To “play it safe,” consumers should only eat fully cooked eggs and make sure “the yolks are firm with no runny parts,” Daisy May, veterinary surgeon with U.K.-based company Medivet, said.
What Are Bird Flu Symptoms In Humans?
Symptoms of bird flu include a fever, cough, headache, chills, shortness of breath or difficulty breathing, runny nose, congestion, sore throat, nausea or vomiting, diarrhea, pink eye, muscle aches and headache. However, the CDC advises it can’t be diagnosed based on symptoms alone, and laboratory testing is needed. This typically includes swabbing the nose or throat (the upper respiratory tract), or the lower respiratory tract for critically ill patients.
How Is Bird Flu Affecting Egg Prices?
This year’s egg prices have increased as production decreased due to bird flu outbreaks among poultry, according to the USDA. A dozen large, grade A eggs in the U.S. costed around $2.99 in March, up almost a dollar from the fall. However, this price is down from a record $4.82 in January 2023, which was also spiked by bird flu outbreaks. Earlier this month, Cal-Maine Foods—the country’s largest egg producer—temporarily halted egg production after over one million egg-laying hens and chickens were killed after being infected with bird flu.
Why Do Poultry Farmers Kill Chickens With Bird Flu?
Once chickens have been infected with bird flu, farmers quickly kill them to help control the spread of the virus, since bird flu is highly contagious and fatal in poultry. The USDA pays farmers for all birds and eggs that have to be killed because of bird flu, as an incentive to responsibly try and curb the spread of the disease. The USDA has spent over $1 billion in bird flu compensation for farmers since 2022, according to the nonprofit Food & Environment Reporting Network.
Is There A Vaccine For The Bird Flu (h5n1)?
The FDA has approved a few bird flu vaccines for humans. The U.S. has a small stockpile of vaccines for H5N1 bird flu, but it wouldn’t be enough to vaccinate all Americans if an outbreak were to happen among humans. If a human outbreak does occur, the government plans to mass produce vaccines, which can take at least six months to make enough for the entire population. Sequirs, the maker of one of the approved vaccines, expects to have 150 million vaccines ready within six months of an announcement of a human bird flu pandemic. Although there are approved vaccines for other variants designed for birds, there are none for the H5N1 variant circulating. However, the USDA began trials on H5N1 animal-specific vaccines in 2023.
Key Background
The virus spreading in cattle recently has experts concerned it may mutate and spread more easily in humans, though the CDC said its risk to the public remains low. Farrar called the cattle infections in the U.S. a “huge concern,” urging public health officials to continue closely monitoring the situation “because it may evolve into transmitting in different ways.” The increased number of mammal bird flu infections since 2022 “could indicate that the virus is looking for new hosts, and of course, moving closer to people,” Andrea Garcia, vice president of science, medicine and public health for the American Medical Association, said. More than 10 human bird flu cases were reported to the World Health Organization in 2023, and all but one survived. Bird flu has devastated bird populations, and 67 countries reported the deaths of 131 million poultry in 2022 alone. Although bird flu typically infects wild birds and poultry, it’s spread to other animals during the outbreak, and at least 10 countries have reported outbreaks in mammals since 2022. Around 17,400 elephant seal pups died from bird flu in Argentina in 2023, and at least 24,000 sea lions died in South America the same year. Besides cattle, bird flu has been detected in over 200 other mammals—like seals, raccoons and bears—in the U.S. since 2022. Although rare, even domestic pets like dogs and cats are susceptible to the virus, and the FDA warns against giving unpasteurized milk to cats to avoid possible transmission.
