San Diego County is now the fifth location in California to detect the bird flu, county officials announced Monday.

San Diego County has a closed sewage system, meaning that its stormwater and wastewater do not intentionally intermix. This greatly reduces, but does not eliminate, the probability that this detection is from an environmental source such as migrating birds.

Three more California dairy herds have been infected with H5N1 bird flu. A new case of human infection has also been reported in Missouri.

Genetic analysis of a bird flu virus detected in a person in Missouri who didn’t previously have contact with animals offers more details on the case, but experts say there isn’t substantial evidence

Last week, a person in Missouri was infected with bird flu despite not having any exposure to animals. The state’s health department said the individual recovered from their illness but that a household contact of the patient had become ill with similar symptoms on the same day.