If it wasn't the 26th anniversary of the Chernobyl nuclear disaster, perhaps the clouds enveloping Moscow would not feel so ominous. But the combination of the mysterious vapor permeating the city's air, and an anniversary laden with toxic memories have turned what the Russian news agency Interfax says is a pollen cloud into a full-scale Twitter freak-out. Tweets like those from @Russian_market, which referred to "chatter on chemical accident in Moscow" have been getting retweeted and, since they first started coming out about an hour ago, have ratcheted up their level of hysteria. They've started coming in all caps, reporting evacuations of Red Square and Pushkin Square.

But as Russia Today reports, the threat of panic seems worse than the threat of poison. "The Emergencies Ministry is advising the public to calm down. It says the clouds are actually composed of birch pollen, not of chemicals from an allegedly burning factory in the Moscow region, as some reported." But those clouds of birch pollen still irritate. "Biologists say birch trees started blooming yesterday, which would also explain why Muscovites have started sneezing. Birch pollen is a strong allergen, so people suffering from hay fever are strongly advised to take the necessary steps."

So, no poison, no mass evacuations. This sounds like little more than digital hysteria. As Gizmodo's Sam Biddle put it: "This may turn out to be the first disaster hysteria caused by app filter."