Africanized honey bees – which are so aggressive toward humans that they're known as "killer bees" – have been found in the San Francisco Bay Area for the first time.
The bees, which swarm aggressively and can be a deadly threat to anyone who might disturb their colonies, were found in Lafayette, about 10 miles northeast of Oakland in the East Bay area.
The discovery was made by researchers from the University of California, San Diego, who have been tracking the Africanized breed of bees as they've moved northward through the state.
Warming temperatures in the Bay Area may have attracted the bees, experts say, although it's hard to estimate the numbers present.
"The sampling is a little sparse up north," said UC San Diego biology professor Joshua Kohn. Still, he added, it's likely there's more than just one colony established in the Bay Area.
"Normally, honeybees forage within about a mile of their hive, though they can go up to about five miles," he said. "There is no way we found a member of the only Africanized bee colony in that region."
Officials with the East Bay Regional Park district said they would be on the alert.
"No one wants to hear about killer bees," noted district spokeswoman Carolyn Jones. "It reminds you of some '70s horror movie — you know, 'killer bees are coming.'"
While the bees can represent a danger to humans, people shouldn't be alarmed, according to Kohn, who along with his research student Yoshiaki Kono reported the discovery in the journal PLOS One.
"An Africanized honeybee out foraging on flowers is no more aggressive than your average European honeybee. Nor is the sting of an individual any different," he explained. "It's only when a hive is disturbed that the level of aggression from Africanized bees is elevated."
Experts say anyone suddenly finding themselves close to an African honeybee hive should move away quickly. If bees begin to approach, you should run at least 100 yards away. In doing so, avoid swatting or crushing any bees, as that could antagonize other bees from the hive.
Jumping in a swimming pool is not recommended, experts say, since the bees have been known to hang around for a considerable amount of time – longer, probably, than a person could hold their breath – waiting for them to resurface.
Upon reaching a safe location, you should call emergency personnel and a local beekeeping professional.