U.S. officials warn doctors about dengue as worldwide cases surge

U.S. health officials on Tuesday warned doctors to be alert for dengue cases as the tropical disease breaks international records.

The virus, which is spread by mosquitoes, has been surging worldwide, helped by climate change. In barely six months, countries in the Americas have already broken calendar-year records for dengue cases.

The World Health Organization declared an emergency in December, and Puerto Rico declared a public health emergency in March.