In other developments, H5N1 was detected in feral cats in New Mexico and more dairy herds in affected states.
An investigation found that the woman had been exposed to backyard poultry before she became ill.
The positive sample was from 1 of 96 culled dairy cows that were tested at slaughter, and none of the meat entered the food supply.
The group also used the contaminated milk samples to examine heat treatment and refrigeration impacts.
Also today the USDA confirmed 6 more outbreaks in dairy herds and announced 5 more poultry outbreaks, all from Minnesota.
Findings underscore the risk to dairy workers and suggest that contaminated milking equipment may be partly responsible for cattle-to-cattle spread.
The team is producing updated versions of the vaccine that more closely match strains circulating today.
The South Asian 2.3.2.1a clade is known to circulate in birds in India and Bangladesh.
Officials have identified a fill-and-finish opening on a production line at a vaccine company partner and said the activity won't disrupt the supply of seasonal flu vaccine.
Tests on an eye swab were positive in testing at the CDC, though respiratory samples were negative.
