Bird flu outbreak highlights potential risks for global food security

Global agrifood systems are weathering the outbreak of a highly pathogenic subtype of avian influenza called H5N1 — more commonly known as bird flu — currently centered in the United States. Veterinary and health experts are fighting to contain the outbreak, which has crossed over into dairy cattle in 12 U.S. states and has infected at least 29 people across nine countries since early 2022 — though transmission to mammals remains rare. While the impact on global food supplies and nutrition is currently low, experts say that the outbreak serves as a warning of how disruptive the virus could be to agrifood systems and how dangerous to animal — and potentially human — health. U.S. public health officials say the commercial food supply is almost certainly safe from the virus itself. But avian influenza outbreaks can necessitate widespread culling of poultry populations in order to contain the spread of the virus, which could lead to shortages of vital sources of animal protein particularly in lower-income settings. “It is an event that sounds an alarm bell,” Thomas Mettenleiter, an expert in animal virus infections at the Friedrich Loeffler Institute, told Devex. “It’s another in a series of events that tells us that these viruses have to be taken seriously.” And it has prompted renewed calls for investment in a “One Health” approach — which recognizes that environmental health, animal health, and human health are all interlinked, and would facilitate a response to outbreaks like avian influenza that works across all three of those areas. But limited resources — particularly in the veterinary and wildlife sectors and especially in lower-income countries — can minimize surveillance efforts, restrict the connections between various sectors, and lead to a late response. “The concept of one health had become the global slogan during the first round of [avian flu] outbreaks in the early 2000s,” Robyn Alders, a veterinarian and One Health expert at the Australian National University, told Devex. “But we haven’t really managed to nail down the implementation, what does it mean, and how do we deal with that significant resource inequity.” Rare crossover into mammals Several different strains of highly pathogenic avian influenza have emerged in recent decades. A clade of the H5N1 strain is currently circulating in North America after first being detected on the continent in late 2021. It rapidly spread to Central and South America and then to much of the rest of the world and is responsible for record numbers of outbreaks in both wild and domesticated birds. In the U.S., it has affected more than 96.9 million birds, according to the Centers for Disease Control and Prevention. The clade is also getting attention because of its crossover into U.S. dairy cattle — a rare occurrence for avian influenza — catching many dairy farmers unprepared. Since March, infections have been detected within 101 dairy herds, although the actual number is almost certainly higher. Though bird flu has crossed over into mammals before, Mettenleiter said there has long been a question about whether the virus will “ever pass solidly, sustainably into a mammalian population or just remain a single spillover. This question has now been answered by nature.” Scientists are still working to understand if there is something specific about the clade that has allowed it to infect dairy cattle. Ian Brown, the chair of the World Organisation for Animal Health-Food and Agriculture Organization joint network of expertise on animal influenzas, cautioned during a World Health Organization-organized press conference earlier this month that the “fact that it’s in a cow doesn’t mean it’s going to automatically jump into other species.” In a few instances, at least, cattle do appear to have presented a transmission route for humans. At least three people in the United States have become ill after working with infected cows, according to the CDC. There has been no evidence of sustained human-to-human transmission, though, and experts agree that the risk of infection — particularly for people who are not interacting with infected animals — is extremely low. And though the presence of the virus in dairy cattle raised fears about the impact on domestic and global food supply, there has been a relatively stable flow of food supplies with no dramatic impact on global nutrition, Madhur Dhingra, the senior animal health officer at FAO, told Devex. In part that’s because U.S. exports largely go to countries that have the capacity to absorb any shocks and could shift quickly to import from other countries if needed, she said. Meanwhile, pasteurizing milk and other food safety measures can neutralize the threat of any spread through cattle products. Those assurances have convinced countries not to ban U.S. beef and dairy. But some import bans on U.S. poultry products remain in place. “Of course, longer-term effects could still be felt in those countries which don’t have such robust capacity to withstand those economic shocks,” Dhingra said, and experts will monitor that. Effects on lower-income countries While the acute impacts on agrifood systems and nutrition appear to be limited, the outbreak highlights the potential risks as avian influenza spreads and evolves. “It’s been causing intermittent problems with poultry production for a number of years,” Alders said. “The impacts of those outbreaks have become more challenging. Where you have poor, insufficient resourcing of the animal health sector, it’s going to be problematic, both for the animals, but also for people who work with the animals and the wider food system.” Of course, microbes know no borders, meaning every country must take the threat seriously in order to keep it at bay. And any outbreak introduces threats to food security and nutrition, particularly in low-resource settings. As poultry are culled to stop the spread of the virus, those critical sources of protein disappear, and the prices of what remains go up. South Africa was forced to cull at least 7.5 million chickens last year to contain outbreaks of two separate strains of avian influenza, leading to shortages of both eggs and poultry. At the same time, the cost of culling is high, both to the farmers and to governments that usually compensate them for their losses. “A lot of resources that could be invested in disease prevention get channeled into putting out these outbreaks,” Dhingra said. Prices also rise as processing plants and other stages in the food production cycle are disrupted in order to sanitize equipment. And the impact extends beyond the agrifood sector. Efforts to bring avian influenza outbreaks under control strain veterinary and health services — particularly in countries where resources are already limited, Dhingra said. How a One Health approach would work A One Health approach that begins with stricter surveillance and quickly alerts experts across the wildlife, animal, and human sectors could help limit outbreaks and curb their potential impacts, Dhingra said. But it will require significant investment, particularly as avian influenza appears in more species. “The big challenge is many countries in the global south lack the financial resources and technical resources for comprehensive surveillance programs,” she said. “Most of the surveillance done is passive surveillance,” — often when a farmer notices that animals appear to be ill and then reports to a veterinary authority. There is no guarantee, though, that that information then gets shared with wildlife or human health authorities, underscoring the need to improve pathways for sharing across these sectors. And surveillance is only the first step. Countries also need to be equipped with the resources to respond quickly when an outbreak is detected. “Wherever possible, when new clades are emerging, we really, really need to try to knock them on the head if we can,” Alders said. That requires a combination of treatment, culling, and even vaccination. The vaccines, which are primarily available for poultry, must be carefully matched to the strain, which means they are “not a panacea for everything,” Dhingara said. And now with the sustained spillover into the dairy cattle population in the United States, there are demands for more intensive research on how the virus makes the jump to other species and whether that will have long-term implications, even as researchers are beginning to look at vaccines for cattle. “The system that takes care of our health, animal health, has got to work together to have a healthy environment that reduces the risk of spillover of virus from wildlife, but also reduces spillback,” Alders said. Experts warn that the future of our food systems and so much more may depend on it.