With an uptick in mosquito-borne illnesses occurring in different parts of the world, the California Department of Public Health is urging travelers to be cautious as they venture out over the holiday season and beyond.

Mexico and Latin America have both seen increased occurrences of the mosquito-borne diseases chikungunya and dengue. The Big Island in Hawaii also has reported a rise in the number of dengue cases, though it has not been reported on any of the other islands.

“We want all Californians to be extra careful when traveling to these regions and take steps to avoid mosquito bites,” said CDPH Director and State Health Officer Dr. Karen Smith. “The mosquitoes that transmit chikungunya and dengue are aggressive daytime biters.”

The CDPH describes chikungunya as a viral disease characterized by an acute onset of fever and severe joint pain. Dengue, another viral disease, is characterized by high fever, severe headache, muscle and joint pain, rash, and in severe cases bleeding manifestations. For both, treatment is supportive, the disease is not contagious person to person, and there is no vaccine.

For 2015, 164 cases of chikungunya and 90 cases of dengue have been reported in California residents, all with a history of travel to areas where transmission of these diseases occurs, according to the CDPH. Of reported cases in 2015, 148 (90 percent) chikungunya and 77 (86 percent) dengue cases had a history of travel to Latin America. The number of reported California dengue cases with a history of travel to Mexico has increased in the last three years, with 80 in 2013-2015 compared to 17 in 2010-2012.

Three California residents have acquired dengue during the recent outbreak in the Big Island in Hawaii. There have been no cases of chikungunya and dengue acquired locally in California. 

CDPH recommends that travelers prevent exposure to mosquito bites by wearing protective clothing and applying insect repellent containing DEET, picaridin, oil of lemon eucalyptus, or IR3535 according to label instructions. DEET can be used safely on infants and children two months of age and older. In addition, make sure that your hotel or lodging has air conditioning or doors and windows with tight-fitting screens to keep out mosquitoes.

Chikungunya was first introduced to the Caribbean in late 2013, and by Nov. 30, over 25,000 confirmed cases were reported from the Caribbean and Central, South, and North America, including over 9,000 cases in Mexico. Dengue transmission has also been prevalent throughout Latin American countries in recent years, and the risk of dengue is present in several Mexican states, including Baja California Sur (where Cabo San Lucas and La Paz are popular tourist areas).

Anyone returning from an affected region that experiences a fever with joint pain or rash within the two weeks following their return should contact their medical provider and tell the doctor where they have traveled. If the doctor suspects chikungunya or dengue, people should protect themselves against mosquito bites until they recover. This will prevent spread of the virus to mosquitoes and potentially humans here in California. 

In October the CDPH reported the invasive species of mosquitoes that can transmit infectious diseases had been detected in a few California counties. In September, the yellow fever mosquito was detected for the first time in San Bernardino and Riverside Counties.  Since 2013, when this species was first discovered in Madera, Fresno and San Mateo counties, it has been found in Tulare, Kern, Los Angeles, San Diego, Imperial, Orange, and Alameda counties. Also in September, the Asian tiger mosquito was detected in Kern and San Diego counties and has expanded in regions of Los Angeles County.

“It is important to know these species of mosquitoes because they are not what we’re used to in California, and they can transmit diseases such as dengue fever, chikungunya and yellow fever,” Smith said. “While the risk is still low in California, infected travelers coming back to California can transmit these viruses to mosquitoes that bite them. This can lead to additional people becoming infected if they are then bitten by those mosquitoes.”