New warning on Zika virus

There's a new warning on Zika virus.

The head of the World Health Organization says "the more we know, the worse things look."

There's more evidence the mosquito-borne virus can cause birth defects and also Guillain Barre Syndrome, which can paralyze muscles.

The majority of cases are mild, but if the virus continues to spread, experts say we could see a public health crisis with more newborns facing severe neurological problems.