US doctors are warning of an emerging polio-like disease in California where up to 20 people have been infected.
A meeting of the American Academy of Neurology heard that some patients had developed paralysis in all four limbs, which had not improved with treatment.
The US is polio-free, but related viruses can also attack the nervous system leading to paralysis.
Doctors say they do not expect an epidemic of the polio-like virus and that the infection remains rare.
Polio is a dangerous and feared childhood infection. The virus rapidly invades the nervous system and causes paralysis in one in 200 cases. It can be fatal if it stops the lungs from working.
Global vaccination programmes mean polio is endemic in just three countries - Afghanistan, Nigeria and Pakistan.
Click "source" to read more.