Dr. Dustin VanOverbeke is an entomologist and professor of biology at the University of Redlands who can comment on the facts and threat level of the "murder" hornet in the United States.
"The name 'murder hornet' has taken off through social media and news reports, spreading increased and likely unnecessary fear over the Asian Giant Hornet (Vespa mandarinia).
"There is no evidence that they have been in North America before late 2019. Are they really invading the United States now? In short, no. That comes with the caveat of not yet.
"In September 2019 some wasps were discovered on Vancouver Island in British Columbia. The nest was located and eradicated. In December 2019 they were confirmed sighted, and a dead specimen was found, in Washington state near the border with Vancouver Island.
"Results suggest that the wasps were from different colonies, so people in Washington state should be on the lookout this year for any individuals. If people are vigilant in reporting any, we stand a good chance at the moment to eradicate this species before it becomes established. Preventing the establishment of any invasive species is important, but it is crucial in this particular case for the protection of Honeybee colonies. Therefore, beekeepers in Washington state should be especially alert.
"It is likely that we are hearing more about them now through social media as just another example of why 2020 is so far not turning out to be a good year. The name 'murder hornet' also helps spread clicks on articles, both increasing awareness, but also unduly increasing fear over an invasion that has not yet occurred. People outside of Washington state are incredibly unlikely to encounter any, and instead there are many reports of false identifications which lead to more unnecessary villainization and destruction of our native wasp species, such as the Eastern Cicada Killer (Sphecius speciosus).
Are they deadly? "They are deadly to the insects on which they feed, including bees, other hornets, and mantises. People who are allergic to bee stings and prone to anaphylactic shock would be susceptible to a sting as well as anyone stung multiple times, just as with a sting from other bees, hornets, and wasps. The likelihood of being stung enough is incredibly low, as findings by Yanawaga et al. (1980) showed that people stung on average of 28 times survived, while the average number of stings to people killed was 58. However, their sting is reported to be excruciatingly painful."
Should we be worried? "For the great majority of North America—no. For locals in Washington state and especially beekeepers there – yes. They should report any potential sightings to the Washington State Department of Agriculture."
Source: Yanagawa, Youichi; Morita, Kentaro (10 October 1980). "Cutaneous hemorrhage or necrosis findings after Vespa mandarinia (wasp) stings may predict the occurrence of multiple organ injury: A case report and review of literature". Clinical Toxicology. Informa Healthcare USA. 45 (7): 803–807.