Doctors find that an increasing number of people are experiencing motion sickness in Japan due to hundreds of aftershocks since the massive earthquake of March 11.
"We are seeing a sharp increase in the number of patients complaining of dizziness," the Mejiro University Clinic, which specialises in ear, nose, and throat conditions, said on its website.
"They are likely experiencing 'earthquake sickness', a condition similar to motion sickness," the hospital's chief physician Hideaki Sakata wrote on his blog.
Residents and rescue workers in the northeastern region, struck by a 9.0-magnitude earthquake on March 11, had felt nearly 400 aftershocks stronger than magnitude 5.0 as of Friday morning.
Countless smaller jolts have also hit, the Japan Meteorological Agency said.
Major local media reported that the conditions have even affected people in Tokyo, more than 300 kilometres away from the offshore epicentres.
Sakata said the sickness can be eased by simply relaxing, and by sticking to fixed routines such as getting up and going to sleep at roughly the same time each day.