Federal health officials have confirmed that the avian influenza virus found in a California child is closely related to strains found in dairy cattle and poultry across the United States.
The case, initially reported Nov. 22, involved a child from the San Francisco Bay Area who tested positive for bird flu. The CDC has since analyzed the genetic sequence of the virus in the child, resulting in the latest update.
"Although the genetic data generated were insufficient to classify the virus as a specific genotype, the virus gene segments sequenced most closely resemble those segments from recent B3.13 viruses detected in California in humans, dairy cattle and poultry,” federal health officials wrote in the update.
The finding establishes a clear connection between the child's infection and the ongoing outbreak in livestock.
Despite this link, health officials maintain that the risk to the general public remains low.
The CDC reported that the investigation into the child’s illness faced several challenges. Saliva taken from the back of the child’s throat showed very low levels of flu viral RNA, which they said made it difficult to sequence using standard methods, but eventually through advanced techniques, they were able to generate partial genetic sequences of the virus.
The CDC's analysis revealed that the virus from the child's case did not show signs of any concerning mutations, suggesting it hasn’t developed any adaptations that could increase the chance of it spreading among humans.
They also noted that the virus is not closely related to the one that severely infected a person in British Columbia, Canada, they said.
The specific source of the child's illness remains unknown, but more surveillance could help connect the dots for future cases, the CDC said.
The agency stated, "Public health surveillance and investigations of all identified cases will continue at the local, state, and federal levels” and said it would continue to monitor for any concerning changes in human cases or the virus.
Despite the ongoing outbreak, health officials stress that human infections with bird flu are rare. The California Department of Public Health noted that bird flu has never spread between people in the United States. In the few cases where human-to-human transmission has happened overseas, it was limited to close contacts of person who was sick.