A rare mystery rash recently popped up in New York City that left health experts scratching their heads to figure out a cause. But that cause has finally been discovered, and NYC's Health Department says raw fish are to blame.

Symptoms included red, painful lumps and swelling on the hands and arms. Some even had difficulty moving their fingers. About 30 cases of the rash - which was caused by a bacterium called Mycobacterium marinum - have been diagnosed to date. The infection, also called aquarium granuloma, is very rare. In fact experts say that there hasn’t been an outbreak in New York City for at least 20 years. So it's no wonder that doctors initially could not figure out what was causing the infection.

They now know that all of the victims admitted to handling live or raw fish at one of NYC's three Chinese fish markets. These markets are located in Manhattan's Chinatown, Brooklyn's Sunset Park and Flushing, Queens.

Health Department officials insist that there is no risk in eating the fish, but they are urging consumers to wear plastic gloves and wash hands when handling raw fish from one of these markets.

So you can buy the fish. And you can eat it. Just don't touch it.

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Health experts say that NYC hasn't seen a case of aquarium granuloma in over 20 years.