The symptoms passengers and others on the train suffered were consistent with those caused by pepper spray, officials said.

CNN: Subway checked for hazardous material; none found

None of the other passengers has exhibited any flu-like symptoms, one health official said.

CNN: Confirmed cases of H1N1 virus approach 900

One aircraft from Tokyo was quarantined in San Jose, California, for several hours after passengers who had joined the plane in Hong Kong showed symptoms of SARS (which later proved misleading).

ECONOMIST: Getting better, or worse? | The