New Delhi – Bird flu has spread from a Colorado dairy farm to a nearby poultry farm, resulting in the infection of five human workers involved in culling the affected birds. The highly infectious avian influenza H5N1 virus, which has pandemic potential, is prompting an urgent effort to develop a vaccine to mitigate its impact.
The US Centers for Disease Control and Prevention (CDC) confirmed four human cases originating from the commercial egg-laying business. The fifth case is awaiting CDC confirmation but is presumed positive.
Source and Spread of Infection
While the exact source and route of infection at the poultry farm are unclear, it is hypothesized that the virus jumped from dairy cattle to the poultry farm. Genomic sequencing of samples from the poultry operation confirmed the presence of the same genotype of highly pathogenic avian influenza found in the nearby dairy herds, according to Eric Deeble, acting senior adviser from the US Department of Agriculture.
This evidence suggests the virus is capable of thriving in multiple animal hosts without significant mutation, a possibility that raises considerable concern among scientists. The ability of a virus to jump between species increases its potential to spread efficiently. Earlier this year, cows in the US began contracting avian flu, which then spread to two humans.
Despite these developments, CDC principal deputy director Nirav Shah emphasized that the risk to the general population remains low and there is no current recommendation for H5-specific vaccines for livestock workers due to the mild symptoms observed and the absence of concerning genetic mutations in the virus.
Human Symptoms and Agricultural Impact
Preliminary analysis of the virus’s genes from one infected poultry farm patient did not show any mutations of concern. The virus’s sequence closely matched that of infected chickens from the same farm and was identical to virus subunits found in Texas and Michigan.
While human symptoms have been mild and recovery swift, the virus’s impact on agriculture is significant. Milk from infected cows is unsafe for consumption, and large-scale culling to prevent further spread, like the 1.8 million birds at the Colorado poultry farm, severely impacts livestock numbers.
Risks to Workers
The culling process appears to elevate the risk of human infection. The five infected workers were involved in loading birds into carbon dioxide gas chambers for culling, according to the Colorado Department of Public Health and Environment. Principal deputy director Shah noted that industrial fans, while cooling the barns, also spread virus-carrying feathers. The culling method required workers to move between potentially infected birds, increasing their exposure.
Despite the extensive use of personal protective equipment (PPE), the high temperatures in Colorado, reaching up to nearly 40 °C (104 °F), made it difficult for workers to maintain protective measures.
An industrial hygienist has been enlisted to develop better strategies for preventing transmission among workers involved in such high-risk tasks.
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