(CNN) -- More than 55,000 cases of dengue, a sometimes deadly mosquito-borne disease, have been reported in a southeastern Brazilian state in the past four months, authorities said Thursday.
The disease has killed 67 people this year in Brazil's Rio de Janeiro state, the state's ministry of health reported. Slightly less than half of the deaths were children under the age of 13, the ministry said.
Brazilian authorities are calling the situation an epidemic.
The ministry of health did not identify whether the deaths were attributed to the more severe form of dengue, dengue hemorrhagic fever, which "can be fatal if unrecognized and not properly treated," the Centers for Disease Control and Prevention said.
The CDC said that with treatment, fatalities due to dengue hemorrhagic fever, which is characterized by abnormal internal or external bleeding, can be less than 1 percent.
Dengue fever, the more common form of dengue, is caused by four closely related viruses. All of them are carried by infected mosquitoes, mainly the Aedes Aegypti mosquito, the CDC said. Watch a report on the outbreak »
It cannot be spread from person to person.
The Rio de Janeiro health ministry said 513 of its 57,010 cases of dengue were that of dengue hemorrhagic fever.
Rio de Janeiro Mayor Cesar Maia said that patients from outside the city are flooding the municipal hospital and that there aren't enough beds to accommodate them, Brazilian newspaper O Globo reported.
The newspaper said the average hospital waits ranged from eight to 28 hours in some places.
One father told O Globo, "I am just watching my son die slowly as we knock on different hospital doors."
The state's secretary of health, Sergio Luiz Cortes da Silveira, acknowledged, "We don't have enough hospitals for these patients." He said the state was appealing for help from pediatricians elsewhere in the country. Watch ill Brazilians being cared for »
Earlier this week, the country's health minister, Jose Gomes Temporao, said that 2,000 people, including members of the Ministry of Health and the military, were working to combat the Aedes Aegypti mosquito, the government reported on its Web site.
At least part of this work, he said, included going door-to-door to inform people of where the mosquitos live. "Without the mosquito, dengue does not exist," he said, according to the government.
The CDC estimates that there are 10 million cases of dengue around the world each year. "It actually is quite common," said Dr. Ali Khan of the CDC. Watch Khan discuss dengue and its prevention »
Mosquitoes carrying dengue viruses breed in stored, exposed water, including places as shallow as jars, discarded bottles and plant saucers, according to the World Health Organization.
Khan emphasized prevention. "Wear long sleeves, loose, baggy pants and make sure you're using good insect repellent."
Symptoms of dengue fever include high fever, severe headache, backache, joint pains and eye pain, nausea, vomiting and a rash, according to the CDC.
There is no vaccine to prevent dengue fever or dengue hemorrhagic fever, the CDC said. E-mail to a friend