The Centers for Disease Control and Prevention in the United States said that four farm workers who work at the same poultry farm contracted bird flu on Monday, bringing the total number of cases to eight.
Concurrent with the incidents is a concerning viral outbreak among livestock that has also infected humans.
Although a fifth case is also suspected, confirmation requires more analysis.
For the American public, the risk is still “low,” according to the CDC. In addition to conjunctivitis, the affected workers reported experiencing “flu-like symptoms.”
In the United States, an odd twist to the bird flu outbreak was discovered in the spring: the disease, which had hitherto only affected poultry and animals, was suddenly being discovered in cows.
The first human infection via a cow was announced on April 1, in the state of Texas.
Two other cases were then reported in Michigan, and in early July, another case was found in Colorado.
That western US state is now seeing the disease spread among both livestock and poultry.
Experts are concerned about the growing number of mammals infected with the disease, though human cases are still rare.
They fear that high circulation could make it easier for a mutation of the virus to develop that would allow it to pass from one human to another.
The CDC renewed its call for precautions for workers in contact with infected cows or poultry.
