 |
 |
LAC DPH Health Alert:
Locally Acquired Case of Dengue in Los Angeles County
September 9, 2024
|
 |
|
|
|
This message is intended for emergency medicine, primary care, urgent care, internal medicine, and infectious disease providers.
Please distribute as appropriate.
| |
Key Messages
- A case of locally acquired dengue has been detected in a resident of Baldwin Park, Los Angeles County. It is the third case of locally acquired dengue in LA County and California.
- Although the risk of widespread dengue transmission in LA County remains low, these cases indicate the presence of infected mosquitoes locally and underscore the need for public education and preventive measures.
- Providers should consider dengue in any patient with acute febrile illness and consistent symptoms, regardless of travel history.
- Providers should report any suspected cases of locally acquired dengue to Public Health immediately by phone.
| |
Situation
A case of locally acquired dengue has been identified in a Baldwin Park resident. Neither the case nor their household members have a history of domestic or international travel. The case has reported mosquito bites at home. They are now recovering. No additional suspect cases have been identified at this time.
Los Angeles County Department of Public Health (LAC DPH) is working with the local vector control district to respond to the situation. The vector control district has increased mosquito trapping and testing activities and is conducting increased mosquito abatement to reduce the risk of additional cases in the area.
This is the first case of locally acquired dengue reported in LA County in 2024. In 2023, the first locally acquired cases of dengue in California were identified in residents of Pasadena and Long Beach.
Overall, the risk of sustained local spread of dengue remains low in LA County.
Dengue cases are, however, on the rise globally and in the United States. Latin America and Puerto Rico are experiencing a record number of cases of dengue this year, which has led to a higher number of travel-associated dengue cases in LA County and the U.S.
Mosquitos thrive in hot weather, increasing the risk of bites and mosquito-borne diseases.
With mosquitoes capable of transmitting dengue present throughout LA County and travel-associated cases on the rise, the risk of sporadic local transmission continues to be a concern.
LAC DPH encourages healthcare providers to suspect and test for mosquito-borne diseases and routinely discuss prevention strategies with patients and travelers.
| |
Actions Requested of Providers
- Obtain a travel history in all patients presenting with acute febrile illness. Ask about a history of travel among household members as well.
- Consider dengue in any patient with acute febrile illness and recent travel (within 14 days prior to illness onset) to areas with frequent or continuous dengue transmission.
- Consider dengue in a patient without a history of travel if presenting with an acute febrile illness and strongly suggestive signs and symptoms of dengue (e.g., fever, thrombocytopenia, leukopenia, aches, pains, rash). (see Clinical Presentation below)
- Order appropriate diagnostic tests for acute dengue infection. Use either one of these dengue test combinations: 1) reverse transcription polymerase chain reaction [RT-PCR] test and an IgM antibody test or 2) a non-structural protein 1 [NS1] antigen test and an IgM antibody test. These tests should be ordered regardless of time since symptom onset. Do not delay appropriate care while waiting for test results to confirm dengue. (see Laboratory Testing below)
- Report any patient suspected to have locally acquired dengue infection to Public Health immediately. (see Reporting below)
- Discuss the importance of mosquito bite prevention with patients and travelers. (see Prevention below)
| |
Background
Dengue is an arbovirus infection caused by any of the four distinct but closely related dengue viruses (DENV-1, DENV-2, DENV-3, DENV-4). People can be infected with dengue more than once due to the four different dengue viruses. Dengue is endemic in many tropical and subtropical regions worldwide and global incidence of dengue in 2024 has been the highest on record.
Dengue is primarily transmitted to humans by the bite of an infected Aedes mosquito. Local transmission of dengue in the United States has been limited, with sporadic cases reported in Florida, Hawaii, Texas, and more recently Arizona and California
| |
Clinical Presentation
Dengue can range from asymptomatic infection or mild illness to severe disease. The typical incubation period is 5-7 days.
Approximately one in four patients develop symptoms and most commonly have a mild to moderate, nonspecific, acute febrile illness. Typical presentation includes acute onset fever accompanied by a combination of the following: headache, retro-orbital pain, myalgia, bone pain, arthralgia, nausea and vomiting, rash, a positive tourniquet test, and leukopenia.
Approximately one in twenty symptomatic patients develop life-threatening disease with severe bleeding, shock, and/or respiratory distress.
Warning signs of severe dengue usually appear as fever starts to decline, and include persistent vomiting, severe abdominal pain, fluid accumulation, mucosal bleeding, lethargy/restlessness, postural hypotension, liver enlargement, and progressive increase in hematocrit.
Persons at increased risk of severe dengue include those with a prior history of dengue infection, infants, older adults (≥ 65 years), pregnant women, and those with chronic medical conditions. A second infection with a different DENV virus from the first infection carries a higher risk of severe disease than the first, third or fourth infection, however any infection can lead to severe disease.
| |
Laboratory Testing
All patients with suspected dengue should be tested with either one of these test combinations:
- A nucleic acid amplification test (NAAT) (e.g., RT-PCR) and an IgM antibody test OR
- A NS1 antigen test and an IgM detection test.
These tests should be ordered regardless of the time from symptom onset, although the test sensitivity of RT-PCR and NS1 antigen tests decrease after the first 7 days. A serum sample is preferred for dengue testing.
IgG detection in a single serum sample should not be used to diagnose acute dengue because it does not distinguish between current and previous infection.
Testing for West Nile virus, a mosquito-borne virus endemic in LA County, should be obtained at the same time as dengue tests. West Nile can have a similar clinical presentation. In addition, cross-reactivity among arboviral antibody tests can result in false positive tests results.
These tests are available at commercial laboratories. If access to commercial testing is not available, testing can be conducted at LAC DPH Public Health Laboratory after obtaining approval from LAC DPH.
| |
Management
No specific antiviral treatment for dengue is available. Treatment is supportive and requires careful volume management. Appropriate triage, management, and follow-up remain the most effective interventions to reduce dengue morbidity and mortality.
Patients with mild symptoms should be advised to stay well hydrated and avoid aspirin and other nonsteroidal anti-inflammatory drugs (such as ibuprofen) because of their anticoagulant properties. Fever should be controlled with acetaminophen and tepid sponge baths.
For at least one week, patients should avoid mosquitoes and use insect repellent to prevent additional spread.
Patients with severe disease require hospitalization. Intravenous fluid therapy is the mainstay of supportive care. Close observation and frequent monitoring in an intensive care unit may be required. Prophylactic platelet transfusions and steroids are not recommended.
| |
Prevention
Preventing mosquito bites is the best way to prevent dengue and other mosquito-borne diseases. While there is an FDA-approved vaccine, it is only approved for children 9-16 years old with previous dengue infection and living in endemic areas. See CDC Dengue Vaccine.
Aedes mosquitoes bite during the day and night and live indoors and outdoors. The best way to prevent mosquito bites is to use insect repellent, wear loose-fitting, long-sleeved shirts and pants and take steps to control mosquitoes in and around the home. Information for the public, including print resources (in English and Spanish) are available on the CDC Preventing Mosquito Bites webpage.
Patients can be referred to their local vector control district to report problems with mosquitoes and request assistance. See flyer.
| |
|
Reporting
Healthcare providers must report any suspected locally acquired dengue to Public Health immediately by phone.
Los Angeles County DPH Acute Communicable Disease Control:
- Weekdays 8:30am–5pm: call 888-397-3993.
- After-hours: call 213-974-1234 and ask for the physician on call.
Long Beach Health and Human Services:
- Weekdays 8am-5pm: call 562-570-4302.
- After hours: call the duty officer at 562-500-5537.
Pasadena Public Health Department:
- Weekdays 8am-5pm: call 626-744-6089.
- After hours: call 626-744-6043.
| |
Additional Dengue Resources
CDC
LAC DPH
- Dengue--resources for the public and healthcare providers
CDPH
| |
This Health Alert was sent by Dr. Sharon Balter, Director, Acute Communicable Disease Control Program, Los Angeles County Department of Public Health.
| |
|
|
|
