Dengue: A growing health threat internationally

In this guest post, Joshua M. Wong, MD, from the Centers for Disease Control and Prevention shares an update about the growing risk of dengue internationally, locally acquired cases in the U.S. and recommendations for clinicians.

In 2023, the highest number of travel-associated dengue cases were reported to CDC since dengue became reportable in the U.S. in 2010. These trends reflect the growing risk of dengue internationally, with at least 23 countries reporting outbreaks in 2023 and more than 5 million cases reported to the World Health Organization. Dengue transmission has been increasing globally over the past two decades and is present in many popular travel destinations for U.S. travelers.

Because most dengue cases reported in the continental U.S. and Hawaii occur in travelers, CDC advises clinicians to counsel patients on preventing mosquito bites, recognize dengue early in patients at risk and test appropriately for dengue. Additionally, the types of mosquitoes that spread dengue are common throughout many areas of the U.S., and local transmission of dengue is possible. Although local transmission in U.S. states has been limited to sporadic cases or limited outbreaks, locally acquired dengue cases have been reported in Florida, Hawaii, Texas, Arizona and California.

Recommendations

• During travel and in the 2 weeks after returning from travel to dengue-endemic areas, clinicians should advise patients to protect themselves against mosquito bites by using Environmental Protection Agency-registered insect repellent, wearing loose-fitting, long-sleeved shirts and pants, and using window and door screens or air conditioning, if available.
• Clinicians should consider dengue in the differential diagnosis when patients with fever present with signs and symptoms of dengue in two groups:
• Travelers returning from an area with endemic dengue transmission.
• Patients with clinically compatible illness who live in areas with competent mosquito vectors (Aedes aegypti or Ae. albopictus) that can transmit dengue.

More about dengue 

• An estimated 40% to 80% of dengue virus infections are asymptomatic.
• Dengue is usually a mild illness. However, it can progress to severe disease with associated shock, severe bleeding or organ impairment in approximately 5% of cases.
• Mortality can be as high as 13% in untreated patients.
• Early clinical findings are nonspecific but require a high index of suspicion because recognizing warning signs and promptly initiating intensive supportive therapy can reduce risk of death among patients with severe dengue to < 0.5%.
• Clinicians should monitor patients closely for warning signs. The presence of warning signs may predict severe dengue in a patient. For those who develop severe dengue, close observation and frequent monitoring in an intensive care unit may be required. Patients with signs and symptoms consistent with dengue can be tested with nucleic acid amplification tests OR DENV NS1 tests AND IgM antibody tests within 7 days of symptom onset. After 7 days post-symptom onset, IgM antibody tests are recommended.
• Dengue is a nationally notifiable disease in the U.S. Report all suspected cases to the local health department.

Additional resources are available from CDC for clinicians and patients.