There's a zombie epidemic spreading across Russia right now: lethargic, fearless, wandering street birds have infested the population in Russia's biggest city, and the government doesn't know what to do about it.

Residents of Moscow are reporting more and more sightings of these strange "zombie pigeons" wandering the streets. Usually, when approached by a human, the birds will flap frantically and take off for safer skies. Now, the birds are just sitting there. They don't react to anything, and ignore oncoming vehicles and people.

Some pigeons are just walking around in circles on the sidewalk. Others have been spotted losing their balance and falling off of window ledges. More still are lying around, resting their beaks on the ground. There have not been any reports of the birds eating brains, but it may only be a matter of time.

Some officials say the pigeons' behavior won't harm humans. Moscow's deputy mayor claims an intestinal infection that can't be passed to humans is to blame. Russia's Federal Veterinary and Phytosanitary Inspection Unit tells a different story: the birds are suffering from something called Newcastle disease, which is highly contagious and can cause eye infections and flu-like symptoms in humans. The country's Veterinary Committee has a third theory that links the pigeons' strange behaviors to lesions seen on dead birds' livers and intestines, caused by salmonella poisoning. Salmonella is definitely dangerous to people.

For now, authorities are asking anyone in Moscow who sees a strange bird to report it to the police. They're waiting for more evidence to confirm one specific cause before taking action.