The number of confirmed cases of the dengue fever outbreak on Hawaii island is now at 49.

The confirmed cases involve 39 adults and 10 children. Thirty-nine of the cases have been Hawaii residents, and 10 have been visitors, according to the Health Department’s website.

The number of confirmed cases increased by 11. On Friday the tally was 38 cases.

Dengue is not endemic to Hawaii, the state Health Department says. However, it is intermittently imported from endemic areas by infected travelers.

This is the first cluster of locally acquired dengue fever since the 2011 outbreak on Oahu.

The largest outbreak of dengue fever in Hawaii occurred in 1944, when an estimated 1,200 people were stricken with the mosquito-borne virus, resulting in several deaths.

There were no subsequent outbreaks in Hawaii until 2001, when 153 people became infected. Health officials at the time believed the virus was brought to Maui by visitors who had traveled to French Polynesia and the Samoan islands. The disease was concentrated in East Maui, but cases were also confirmed on Oahu, Kauai and Hawaii island.

From 2002 to 2009 the number of dengue cases ranged from three to 14 per year.

Symptoms usually begin five to six days after a patient is bitten by an infected mosquito, but the onset can range from two to 15 days. Symptoms include a sudden fever, severe headaches, pain behind the eye, joint and muscle pain, and rash — typically on hands, arms, legs and feet three to four days after the fever starts.

The disease cannot be spread from person to person.

Hawaii County Civil Defense will hold the last two of its information briefings on dengue fever this week. They will be at 6 p.m. tonight at Hilo High School cafeteria and 6 p.m. Tuesday at Keaau High School cafeteria.