(AP) -- The World Health Organization says an outbreak of hand, foot and mouth disease has surged in Vietnam, killing 98 children and sickening more than 42,000 others this year.

It says three-quarters of the deaths have been in children three years old or younger.

This year's outbreak is a sharp increase over previous years. Since 2008, about 10,000 to 15,000 cases were reported per year, with about 20 to 30 children dying annually.

The WHO statement quoted Vietnam's health minister as warning that cases might increase in coming months when preschools and kindergartens resume.

The disease is spread by sneezing, coughing and contact with fluid from blisters or infected feces. No vaccine exists, but illness is typically mild and most children recover quickly.

Explore further Vietnam on alert as common virus kills 81 children

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