An unidentified form of pneumonia has broken out in the central Chinese city of Wuhan, prompting authorities to quarantine those infected and raise hospital alerts.

Axar.az reports citing Time that Wuhan’s health bureau announced Sunday that close to 60 patients have been diagnosed with the virus, and neighboring Hong Kong has announced suspected cases. (A suspected case in Singapore turned out to be a false alarm.)

The mysterious strain has been linked to a seafood market that has been closed for sanitation since Jan. 1. Medical experts are attempting to identify the illness. While they say it is unlikely that this new strain of pneumonia could cause a repeat of 2003’s deadly SARS outbreak in 2003, which killed hundreds in mainland China and spread as far as the U.S. and Canada, they stress that vigilance should not be relaxed.