The CDC is investigating samples from a 42-year-old patient in Brazil who died after contracting H1N1, a type of flu that spreads among pigs, the World Health Organization said June 16. It's unclear how the woman caught the virus.
Brazil notified the WHO of the case June 7, after confirming the case was caused by H1N1, a subtype of influenza A. The woman had "underlying medical conditions" and lived near a swine farm, though did not have any direct contact with pigs, according to health officials. Ongoing investigations confirmed two of her close contacts worked at the swine farm, but did not develop respiratory disease and tested negative for influenza.
"Based on the information currently available, WHO considers this a sporadic case, and there is no evidence of person-to-person transmission of this event," the agency said. "The likelihood of community-level spread among humans and/or international disease spread through humans is low."
Countries are required to notify the WHO of all human infections caused by a novel influenza subtype under the International Health Regulations.
The CDC studies thousands of sequenced flu viruses each year through its collaboration with the WHO, according to CBS News. The CDC did not immediately respond to the news outlet's request for comment.