Number of rare local dengue cases ticks up in Los Angeles County

Los Angeles County is now reporting 11 locally acquired cases of dengue this year -- about double the number of local cases of the mosquito-borne disease reported in the county at the beginning of the month.

County health authorities reported the two most recent cases Wednesday, both in residents who had no history of recent travel.

“These two additional cases raise concerns about the potential for continued local spread of dengue in our community," said Dr. Muntu Davis, the Los Angeles County health officer, in a statement.

Davis urged local doctors to be vigilant and to consider testing for dengue in patients with symptoms -- even if they haven't recently traveled, which is more commonly how the disease spreads.

Being able to trace and account for all new cases allows local officials to adequately prioritize mosquito control and prevention measures to reduce the risk of spread, according to the statement.

Dengue viruses spread through mosquito bites.

The most common symptom is a fever with aches and pains, nausea, vomiting and rash. Symptoms usually begin within two weeks of being bitten by an infected mosquito and last 2-7 days. Most people recover after about a week.

Locally acquired cases mean that the people infected have no history of traveling to an area where dengue normally spreads.

Local dengue transmission is typically common in tropical and subtropical areas of the world -- including Florida and U.S. territories in the Caribbean.

Last year, there were only two locally acquired cases reported in the state of California, and those were the first local cases in the state reported in over a decade, according to data from the Centers for Disease Control and Prevention.

The CDC issued a health alert in June warning health care providers of an increased risk of dengue virus infection this year.

The first case of locally acquired dengue in Los Angeles County this year was reported Sept. 9.

Overall, there have been 4,439 locally acquired dengue cases in the U.S. -- the vast majority in Puerto Rico. In addition to the 11 cases in California, Florida has reported 49 cases this year.

The best way to prevent dengue is to avoid mosquito bites, according to the CDC.

ABC News' Youri Benadjaoud contributed to this report.