A fourth dairy worker in the United States has tested positive for bird flu following exposure to infected cows, marking the first human illness detected in Colorado related to an ongoing outbreak in cattle. This case follows three previous cases, with the second one occurring in Michigan. While some individuals exhibited symptoms such as coughing, the other three cases, including the most recent one in Colorado, have only presented with eye symptoms, like redness. The culprit behind these infections is a bird virus called influenza A(H5N1). This subtype of flu was first observed among wild birds. Since then, numerous poultry farms across the country have reported cases of birds testing positive for the virus. Recent research suggests that when this virus infects cows, it can contaminate the animals’ milk and persist even after harvest. This poses a significant risk to dairy workers, who may come into contact with contaminated milk through direct contact with cows or with milking equipment. However, the pasteurized milk supply remains safe because the pasteurization process effectively inactivates any viruses present in the milk. Due to the risk associated with raw milk, the CDC recommends that individuals avoid consuming it.
In the recent Colorado case, the individual was under surveillance due to their exposure to H5N1-infected cattle at their workplace. Clinical samples collected from the person were sent to the CDC for analysis, which confirmed an infection with an influenza A(H5) virus. The agency is currently conducting further analysis to definitively confirm the virus as H5N1. The infected person received treatment with a common antiviral drug used for seasonal flu, known as oseltamivir, or its brand-name version, Tamiflu. Following this treatment, the person fully recovered. Notably, all three individuals previously infected during this outbreak also recovered from their mild infections. However, it’s important to remember that in the past, H5N1 has been known to cause severe illness and death in some individuals.
Overall, the Colorado case does not alter the CDC’s overall assessment of the ongoing outbreak. The agency has been diligently monitoring influenza surveillance systems, particularly in affected states, and has not observed any unusual influenza activity among the general population. Based on the current available information, this infection does not necessitate any adjustments to the CDC’s current H5N1 bird flu human health risk assessment for the U.S. general public, which is considered to be low. Nevertheless, the CDC remains vigilant and continues to closely monitor for any unusual flu activity. There is a possibility that, over time, H5N1 could acquire mutations that allow the virus to spread easily from person to person, a capability it currently lacks. Such a genetic alteration in the virus would be a cause for concern, as it could potentially trigger a widespread outbreak or even a pandemic.
