Continual occurrences of bird flu have ravaged poultry populations and wild birds throughout the United States and globally. The H5N1 virus, notorious for its impact, is now showing increasing compatibility with mammals and has been detected in felines, goats, and raccoons. Its reach in the US has extended to at least 170 dairy herds across 13 states. Furthermore, in April, authorities confirmed the transmission of the virus from an infected cow to a dairy farm employee, marking the first crossover of the virus from a mammal to a human.
Presently, there is a noticeable rise in the number of individuals contracting bird flu. On July 25, the US Centers for Disease Control and Prevention verified an additional three human cases, incrementing the total count of cases in the US to 13 since April. These infections were identified among individuals in direct contact with infected poultry at an egg farm in Colorado, which had reported an outburst of H5N1 among its avian population. All affected individuals exhibit mild symptoms and have been provided with Tamiflu, an antiviral medication. As per the CDC, the general risk of contracting H5N1 among the public remains low.
“Given these people’s direct involvement with infected poultry, these cases are somewhat anticipated,” remarked Stephen Morse, an epidemiologist at Columbia University in New York. “Fortunately, there is no evidence of person-to-person transmission so far. If that were to occur, our concerns would escalate significantly.”
The CDC is investigating whether the personnel in Colorado wore proper personal protective gear, including gloves, coveralls, footwear, masks, and goggles. The agency states that historically, the majority of human bird flu cases have emerged in individuals not utilizing the recommended protective equipment.
These recent cases emerged closely following the identification of another cluster of human infections earlier in the month. On July 19, the CDC confirmed six human cases of bird flu among poultry workers at a separate Colorado facility. These cases involved individuals engaged in the disposal of birds infected with H5N1. When the virus is identified on a farm, all birds are culled as a precaution. With the latest three cases, Colorado now has a total of nine confirmed bird flu cases.
The remaining four cases – one in Texas, two in Michigan, and one in Colorado – stemmed from contact with infected dairy cattle. The probable transmission route was through the consumption of unpasteurized milk. A report released in May revealed that the virus can persist on milking equipment for at least an hour, heightening the risk of infecting individuals and other animals. Fortunately, pasteurization eradicates the H5N1 virus from milk sources.
While the reported US cases this year have exhibited mild symptoms, H5N1 has historically displayed a fatality rate of approximately 50 percent. From 2003 to 2023, there were 878 confirmed positive cases of the virus, resulting in 458 reported deaths.
The last significant outbreak of H5N1 among US poultry was in 2015, resulting in the demise of 50.5 million birds. It wasn’t until April 2022 that the first human bird flu case was reported in a poultry worker in Colorado. Subsequent cases were not documented until this year. Anice Lowen, a flu expert at Emory University in Atlanta, Georgia, notes, “There has been a shift. Whether this is due to modifications in the virus or alterations in exposure circumstances is uncertain without further information.”
