# **H5N1 Bird Flu Reaches Dairy Worker in Nevada: Essential Information**
A dairy worker in Nevada has contracted a variant of the H5N1 bird flu—genotype D1.1—that has recently transitioned to cows, confirmed by the Centers for Disease Control and Prevention (CDC). This case represents a remarkable development in the ongoing H5N1 outbreak that has been affecting dairy cows across the U.S.
## **Infection Details**
The affected worker showed conjunctivitis (commonly referred to as pink eye) as the sole symptom and is currently on the mend, according to a press release from the [Central Nevada Health District](https://www.centralnevadahd.org/press-release/). This case is significant as it is the first documented occurrence of the D1.1 genotype transferring from birds to cows and subsequently to a human.
H5N1 clade 2.3.4.4b, genotype D1.1, is the main variant present among wild birds in North America. It was first identified in cows in Nevada last week through bulk milk tests performed by the U.S. Department of Agriculture (USDA). Previously, the outbreak affecting dairy cows—announced in March 2024—was attributed to a different genotype, B3.13, believed to have stemmed from a singular spillover incident from wild birds to cows in Texas around late 2023 or early 2024.
## **Instances of H5N1 in Humans in the U.S.**
Since the start of the outbreak, the CDC has verified **68 human cases of H5N1 in the U.S.**, including:
– **41 instances in dairy workers**
– **23 instances in poultry workers**
– **1 instance linked to backyard/wild bird exposure in Louisiana**
– **3 instances with unclear infection sources**
Most of these cases have been mild, presenting with symptoms such as conjunctivitis or slight respiratory issues. However, the D1.1 genotype has been associated with more serious cases, including a **fatal infection in Louisiana** and a **severe case in a Canadian teenager** requiring intensive care.
## **Genetic Insights and Possible Hazards**
The USDA and CDC are actively observing the genetic progression of the virus. A recent investigation revealed that the D1.1 strain affecting cows in Nevada carries a **significant mutation (PB2 D701N)**, which facilitates bird-adapted viruses to replicate more effectively in mammals. This mutation has not been detected in the B3.13 genotype circulating in dairy cows or in D1.1 variants found in wild birds, though it was previously noted in a **2023 human case in Chile**.
Despite the presence of this mutation, the CDC has declared that:
– No additional concerning mutations have been detected.
– The virus is not predicted to alter its interaction with human immune responses or anti-viral treatments.
– There is **no proof of human-to-human transmission** currently.
## **Current Risk Evaluation**
While the CDC assesses the overall risk to the broader public as low, individuals who interact closely with poultry, dairy cows, and wild birds face a heightened risk of exposure. Health officials suggest that these workers implement appropriate precautions, including wearing protective equipment and maintaining good hygiene practices.
To date, **967 herds across 16 states** have contracted H5N1 bird flu, and **almost 158 million commercial birds** have been impacted since 2022. The CDC and USDA continue to monitor the situation diligently to prevent additional spread and evaluate any potential public health risks.
## **Summary**
The appearance of H5N1 genotype D1.1 in dairy cows and its transmission to a human in Nevada is a troubling progression in the ongoing bird flu situation. Although the risk to the general public stays low, this development highlights the necessity for ongoing monitoring and precautionary measures to curtail the virus’s spread.
For the latest updates, check out the [CDC’s official bird flu page](https://www.cdc.gov/bird-flu/situation-summary/index.html).
