The spread of bird flu in California has surpassed predictions, causing concerns among dairy farms.
Farmers and vets in California are sounding the alarm as they observe the infection striking dairy herds more severely than in other states, leading to higher rates of sick and deceased cows within affected herds. No indications of escalating illness have been noted in people. Similar to the initial two human cases in California, this latest instance involves a farmworker who had contact with ailing dairy cattle. Investigators have yet to detect any links between this recent occurrence and the previous two, suggesting another instance of animal-to-human transmission, as stated by the California Department of Public Health in a public announcement. Symptoms in all three cases were mild, featuring red and inflamed eyes, a telltale sign of conjunctivitis.
Dr. Nirav Shah, the CDC's Principal Deputy Director, stated during a press conference on Friday that these cases were not unexpected.
"Additional cases may continue to be identified as more herds continue to test positive," Shah claimed.
Although public health officials are dealing with the infections in a measured manner, experts outside the field are raising concern over every new human infection. According to Dr. Jennifer Nuzzo, who runs the Pandemic Center at Brown University, such reports underscore her fears that if unchecked, the virus will result in severe health issues for people.
"Many individuals have underestimated the threat posed by H5N1 on farms, relying on a limited number of mild incidents to assume safety. Yet epidemiologists know that the higher the number of infections, the more likely we'll see severe outcomes," Nuzzo explained in an email to CNN.
Nuzzo further expressed her concern, stating, "I have yet to be reassured that this virus will not result in hospitalizations or fatalities."
Since late August, more than 80 herds in California have been impacted by bird flu, as confirmed by the United States Department of Agriculture's most recent update. California, being the nation's largest milk producer, has been applying bulk milk tank sampling in areas with positive test results.
Dr. Eric Deeble, acting senior advisor for the USDA's H5N1 response, mentioned during the press conference that the testing has assisted in promptly identifying additional affected herds in a similar manner to Colorado, where bulk milk tank testing was mandated by the state.
The USDA has dispatched a strike team to assist California in tracking the outbreak's expansion, while the state is exploring ways to broaden its milk testing beyond areas with known infections. Farmers in California, however, have raised concerns about the H5N1 infection in their herds being considerably more severe than reported in other states. In other states, roughly 10% of cows in an affected herd have shown symptoms, resulting in the death of less than 2% of the animals, as reported by the American Veterinary Medical Association.
In contrast, California dairy farms are reporting that the virus is infecting 50% to 60% of their herds, and 10% to 15% of the cows are succumbing to their infections, as reported by the California Dairy Quality Assurance Program. The higher infection and fatality rates in California were first disclosed by the Los Angeles Times.
Scientists are questioning whether environmental factors, such as heat, or if the virus itself is adapting and causing more severe infections are contributing to this increase in severity. Researchers would be better equipped to determine if genetic modifications to the virus are playing a part if state and federal officials were to release more comprehensive information about the viruses they are finding.
The initial infected herds in California were detected in late August. On Monday, the CDC unveiled the gene sequences of viruses isolated from the first two farmworkers in the state to test positive to a widely used data sharing site called GISAID.
Further sequences from dairy cattle in the United States, shared by the USDA's Animal and Plant Health Inspection Service, can be found in the database, but these sequences lack crucial information required to place them within the broader outbreak context, such as the state of origin and the collection date.
The USDA states that it adheres to the same procedure throughout the outbreak, uploading raw sequences every Friday as they become obtainable and generally within two weeks of sample collection. The agency adds additional information about the sample, including the collection's state and date, around six weeks later after the epidemiological investigation has been concluded.
Other nations, such as some in Africa, succeed in sharing the sequences of viruses within days and typically with more details than are being provided by the USDA, according to a GISAID spokesperson.
Without this information, it is challenging for researchers to trace the virus's evolution and understand whether it is transforming to pose a more significant threat.
Despite the mild symptoms observed in the three reported human cases, Dr. Jennifer Nuzzo expresses concern that the higher number of infections in animals could lead to more severe health issues in people. The infection rates and fatality rates for cows in affected California dairy herds are significantly higher than in other states, leading scientists to question if environmental factors or genetic modifications to the virus are contributing to the increased severity.
