The health secretary of Puerto Rico declared an epidemic on Monday due to a rise in the number of dengue cases.

The United States territory, with a population of 3.2 million individuals, has documented a minimum of 549 instances thus far in the current year, in contrast to a combined total of 1,293 cases throughout the previous year. Most of the cases have been recorded in the capital city of San Juan.

Over 340 individuals have been admitted to the hospital for the illness transmitted by mosquitoes, as reported by the health agency on the island.

In 2012, Puerto Rico’s last recorded a dengue outbreak.

The World Health Organization has reported a total of over 5 million dengue cases worldwide in the past year, with almost 80% of these cases occurring in the Western Hemisphere. This region has already seen 3 million cases this year and health experts attribute the increase to a combination of heavy rain, humidity, and heat related to climate change.

The virus can result in severe headaches, fever, vomiting, a skin rash, and other symptoms. Although many individuals infected with the virus may not exhibit any symptoms, serious cases can result in plasma leaking and possibly death.