Brazilian army joined health care experts this week to fight against the deadliest outbreak of dengue fever to hit Rio de Janeiro in the recent years.

During the past four months, more than 55,000 cases of dengue have been reported in Brazil. The disease has already killed 67 people this year in Rio, according to the state’s ministry of health, CNN Web site reports. Slightly less than half of the deaths were children under the age of 13, the ministry said.

Dengue fever – which is transmitted by mosquitoes – comes in several strains and is difficult to diagnose, according to the U.S. Centers for Disease and Control. The disease is also known as “bone-break fever” and often causes severe joint pain, elevated body temperature, diarrhea, vomiting and bruising. People who suffer repeat infections from different strains run the risk of potentially fatal internal bleeding. No vaccine is yet commercially available.

Moreover, dengue hemorrhagic fever, one of the most severe forms of dengue “can be fatal if unrecognized and not properly treated,” the CDC says. There are nearly 10 million cases of dengue worldwide each year, the CDC estimates.

The number of patients seeking treatment overwhelmed public hospitals in the northern and western districts of the city. Many people complained about long delays.

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.

Therefore, more than 1,200 military personnel arrived in Rio this week to help fighting against dengue, by spraying insecticide in hard-hit neighborhoods and by erecting emergency hospital tens.

Rio de Janeiro health officials have recommended that children wear long pants, socks and shoes, not sandals, to prevent mosquito bites.