(Bloomberg) -- Mounting cases of bird flu in humans is luring the day trading crowd to snap up stock in vaccine developers. It’s a familiar setup for industry veterans who have witnessed past trading frenzies at the first signs of an outbreak. 

Shares of CureVac NV, which has a bird-flu vaccine in early-stage testing, jumped 15% Wednesday as concerns grow over a potential outbreak of bird flu in humans following reports of a new case in Australia. Novavax Inc. — which recently touted its plans to explore an avian flu vaccine — gained for the third day closing at its highest level since December 2022. 

Shares of Moderna Inc. rose 2.9% in afterhours trading while Pfizer Inc.’s gained 1.4% following a report that the companies are in talks with the US government about the development of vaccines for bird flu. Moderna and fellow Covid shotmaker BioNTech SE notched double-digit advances in regular trading, while Pfizer rose 3.6%. 

Read more: Second US Human Bird Flu Infection Reported in Michigan

“Bird flu is adding momentum to stocks that were already going higher,” Jared Holz, a health-care specialist at Mizuho said. “A lot of it is probably just big picture — more retail-oriented trading on the back of these headlines linking the problems that are arising with bird flu with the vaccine stocks.”

Past outbreaks like Ebola, Zika and monkey pox have spurred similar swings — particularly for smaller players — as companies come out of the woodwork touting their plans for a vaccine or treatment. Day trader chatrooms search for potential winners but only a handful may eventually emerge — if at all — with successful treatments. Even fewer stocks end up becoming household names like Moderna or BioNTech.

So far, the stocks’ reactions have been “fairly extreme,” Holz said. He recommended selling into the strength as its as of yet unclear if the illlness will spread or have any impact on revenue, though “the story is definitely catching on more.”

Read more: US Bird Flu Surveillance Gets $100 Million Funding Boost 

Many of the vaccine names had been jumping prior to the newly reported case. Novavax’s stock has been soaring ever since it inked a license pact with Sanofi — and revealed its bird flu plans — two weeks ago. A rally in Moderna shares kicked off after a recent patent win against Pfizer. 

--With assistance from Matthew Griffin.

(Updates with afterhours trading.)

©2024 Bloomberg L.P.