Dengue Outbreaks

Dengue Outbreaks March 2025

According to the World Health Organization (WHO) and numerous health agencies, Dengue is a viral infection spread to humans by infected mosquitoes of the Aedes genus and a leading cause of febrile illness among international travelers. More than 13 million dengue cases were reported in 2024, making it the highest year on record. The WHO has classified Dengue as a grade 3 emergency, with an estimated 4 billion people at risk globally. As of March 26, 2025, the WHO data dashboard indicates Dengue is endemic in about 100 countries, including areas within the United States. An analysis published in December 2024 revealed a clear link between climate change and the proliferation of vectors into new territories associated with increased disease incidence.

On January 20, 2025, the WHO published a Global Strategic Preparedness, Readiness, and Response Plan for Dengue. Dengue's four subviruses are usually spread to people through the bites of infected Aedes mosquitoes. On October 3, 2024, the WHO launched the Global Strategic Preparedness, Readiness, and Response Plan to tackle Dengue and other Aedes-borne arboviruses. The WHO plan aligns with the Global Vector Control Response 2017-2030, a global strategy to strengthen vector control worldwide, and the Global Arbovirus Initiative. As of December 2024, the European Centre for Disease Prevention and Control (ECDC) reported over 8,500 dengue-related deaths. The U.K.The  Health Security Agency (UKHSA) says that local dengue fever does not occur in the United Kingdom but has been acquired from traveling to dengue-endemic areas. 

An analysis published in July 2024 reported that the most frequent regions of dengue infection acquisition were Southeast Asia (50.4%), South Central Asia (14.9%), the Caribbean (10.9%), and South America (9.2%). The median age was 33 years, and tourism was the most frequent reason for travel (67.3%).

Mosquitoes that spread Dengue viruses usually live below 6,500 feet elevation; therefore, a person's chances of getting Dengue in high altitudes are very low. As of 2025, HealthMap has published dengue case maps. People with suspected DENV infection should be tested at commercial labs with RT-PC, NS1 antigen test, or an IgM enzyme-linked immunosorbent assay (ELISA) antibody test. 

Dengue Outbreak Travel Advisories

The U.S. Centers for Disease Control and Prevention (CDC) published a Health Update (CDCHAN-00523) on March 18, 2025, highlighting the ongoing risk of Dengue virus infections and updates to testing recommendations in the United States. The CDC reissued a Global Travel Health Notice on March 20, 2025, regarding Dengue outbreaks in the Americas, Africa/Middle East, and Asia/Pacific regions. The CDC has not issued travel advisories for cities reporting local dengue outbreaks in the U.S., such as Los Angeles, CA, and Miami, Florida.

Dengue Outbreak in the United States

The U.S. CDC reported on March 19, 2025, that 1,158 travel-related Dengue cases and one local case have been reported in 28 jurisdictions this year. Transmission of Dengue virus serotypes (DENV-1, -2, -3, and- 4) remains high in the U.S. territories of Puerto Rico and the U.S. Virgin Islands. DENV-3 is the most common (84%) serotype identified in 2025.

In 2024, 53 jurisdictions, led by Arizona, California, Florida, New Jersey, New York, and Puerto Rico, reported 9,391 dengue cases as of December 31, 2024. In 2023, 52 U.S. jurisdictions reported 6,164 dengue cases to the CDC. In June 2024, the CDC updated a Health Alert Network Health Advisory, notifying healthcare providers, public health authorities, and the public of an increased risk of dengue virus infections in the United States. The CDC says clinicians should consider Dengue in patients with fever who live in or recently traveled to areas with a risk of Dengue.

As of December 2024, the Florida Health Department (FDH) reported over 999 travel-associated and 91 locally acquired dengue cases throughout the state, mainly in Miami-Dade County. 

The Texas Department of State Health Services (DSHS) says mosquitoes that transmit dengue fever are found in Texas. As of February 4, 2025, DSHS has not reported any dengue cases. As of December 2024, (143) imported dengue cases in 23 Texas counties, led by Travis (18), Dallas (19), one local case  (Cameron County), and one related fatality. Texas reported 79 travel-related dengue cases in 2023 and one locally acquired case in Val Verde County.

In California, the San Bernardino County Public Health Department reported (1) a locally acquired dengue case in San Bernardino on November 7, 2024. The Los Angeles County Department of Public Health has reported 12 locally acquired dengue cases in the San Gabriel Valley in the cities of Baldwin Park (8), El Monte (2), Hollywood Hills (1), and Panorama City (1) in 2024. In San Diego, Escondido, and Vista reported dengue cases in 2024. Over 360 dengue cases were confirmed in California in 2024: California reported two locally acquired cases (Long Beach and Pasadena) and 250 travel-related cases in 2023.

Between 2010 and 2023, 250 locally acquired cases were reported in Hawaiʻi.

Dengue Outbreak U.S. Territories

The CDC says the Dengue virus is endemic in the U.S. territories of Puerto Rico, American Samoa, the U.S. Virgin Islands, the Federated States of Micronesia, the Republic of the Marshall Islands, and the Republic of Palau. In the U.S. Virgin Islands, a dengue outbreak was declared in August 2024 and remains in effect in 2025. A total of 208 locally acquired cases were identified in 2024 and 30 in 2025, all on the island of St. Croix. The Virgin Islands Department of Health urged residents to take immediate precautions to prevent further dengue transmission as cases surged in the St. Thomas-St. John area. John area. John and St. Croix Districts.

In Puerto Rico, a public health emergency was declared in March 2024 and remains in effect in 2025. As of March 7, 2025, 936 cases have been reported, representing a 113% increase compared to the same period in 2024. In 2024, 6,291 cases were reported, and 13 deaths were reported. Puerto Rico's Department of Health confirmed that Dengue was endemic in the greater San Juan area, with 4,467 cases. 

Of American Samoa school-aged children, the estimated seroprevalence among those aged 7–16 was 59%.

Dengue Outbreaks in Africa

Dengue circulation has been detected in more than 30 African countries. According to the Africa CDC Epidemic Intelligence Report, as of January 2025, over 1,300 dengue cases have been reported in Africa. As of 2024, over 74,000 dengue cases have been reported this year from Burkina Faso, Cameroon, Cabo Verde, Central African Republic, Chad, Côte d'Ivoire, Ethiopia, Ghana, Kenya, Mali, Mauritius, São Tomé and Príncipe, Senegal, Sudan, and Togo. The ACDC reported in 2024 that travelers visiting these African countries may be at increased risk for Dengue. In 2023, 171,991 dengue cases and 753 deaths were reported in African countries.  The U.S. CDC issued a Travel Health Notice in 2023, confirming Dengue is an ongoing risk in Africa. A December 2025 study found that countries in eastern Africa had a high estimated risk of dengue importation from Asia and other eastern African countries. In contrast, for west African countries, the risk of importation was higher from within the region than from countries outside of Africa.

Dengue Outbreaks in the Americas

The first suspected dengue-like epidemics were reported in 1635 in Martinique and Guadeloupe. The Pan American Health Organization (PAHO) issued an Epidemiological Alert confirming dengue outbreaks. As of March 19, 2025, over 1.2 million Dengue cases and 348 related fatalities have been reported in the Americas this year. As of December 31, 2024, 49 countries and territories have reported over 13,017,982 Dengue cases and 8,151 related deaths in the Americas in 2024. In 2023, 4,617,108 Dengue cases were reported in the Americas.

Argentina's Epidemiological Bulletin reported over 580,000 dengue cases in 2024, with 56,435 in Buenos Aires. Argentina's Ministry of Health published a Comprehensive Preparedness and Response Plan for Dengue Epidemics 2024-2025.

Over the past 25 years, nearly 18 million Brazilians have been infected with the dengue virus. As of January 3, 2025, Brazil's Ministry of Health weekly Arboviruses reports indicate over 9.6 million dengue cases and 5,441 related deaths in 2024. TheSão Paulo dengue data dashboard was updated in February 2025. In 2023, Brazil reported about  2.9 million patients, a one-year increase of 20%. In 2023, Rio de Janeiro reported 22,959 dengue cases. The Brazilian Ministry of Health reported dengue cases among pregnant women reached 5,151 in the first six weeks of 2024, compared to 1,157 in the same period in 2023.

On August 16, 2024, the Republic of Trinidad and Tobago confirmed 825 cases of Dengue Fever and eight (8) laboratory-confirmed deaths. The Caribbean reported over 62,000 dengue cases in 2023, a significant increase from 20,349 cases in 2022. Jamaica's Ministry of Health declared a dengue outbreak on September 23, 2023. 

Dengue is hyperendemic in Colombia. It imposes a substantial economic burden on patients, caregivers, society, and the national health system. In 2025, Colombia's Huila Department declared a public health emergency.

According to the Republic of Costa Rica Health Surveillance Directorate, 1,076 dengue cases were reported in 2024. Costa Rica confirmed over 24,000 dengue cases in 2023, with the Huetar Caribe and Central Sur regions presenting the most cases. As of August 4, 2023, all four dengue serotypes were registered.

In French Guyana, over 8,000 confirmed dengue cases have been reported since the beginning of 2024.

The U.S. CDC includes Mexico in its global Level 1 Dengue Travel Health Advisory. As of February 2025, Mexico has reported over 10,000 dengue cases. In 2024, Mexico confirmed about 549,000 dengue cases. A May 2024 model predicted that the percentage of municipalities affected by Dengue will rise from 55 to 91% in Mexico. Dengue was reported in 28 of 32 Mexican states in 2023, and transmission has been documented in Yucatan since 1979. All four DENV serotypes have been found in Mexico for decades. Between 1995 and 2008, constant circulation of DENV-3 was recorded in Mexico. Furthermore, a notable increase in circulation was observed in 2022 (25%), 2023 (59%), and 2024 (86%).

In Nicaragua, 92,022 dengue cases were reported in 2024. A study published on January 10, 2025, demonstrates differences in dengue severity by serotype and immune status and emphasizes the critical need for a dengue vaccine with balanced effectiveness against all four serotypes, mainly as existing vaccines show variable efficacy by serotype and serostatus.

DENV was reintroduced in Panama in 1993 after a 35-year absence of autochthonous transmission. The increase in the number of total dengue cases has been accompanied by an increase in severe and fatal cases, with the highest case fatality rate recorded in 2011. All four serotypes were detected in Panama. An analysis published in 2024 suggests that Panamanian strains were related to viruses from different regions of the Americas, suggesting a continuous exchange of viruses.

Paraguay's Ministry of Health confirmed that the DENV-3 subtype returned in 2025 after nine years.

Peru issued an Alert in November 2024, notifying public and private health facilities of the increased risk of dengue infections. On November 23, 2024, a dengue vaccination program was launched in 16 districts of Loreto, Piura, Tumbes, and Ucayali regions.

Dengue Outbreaks in Asia and the Pacific Islands

Dengue has become an annual epidemic in many parts of Southeast Asia. In 2025, the U.S. CDC reported that the WHO Western Pacific Region countries are reporting higher-than-usual dengue cases, and travelers visiting these countries may be at increased risk: Bangladesh, Cambodia, Hong Kong, Indonesia, Fiji, Malaysia, Nepal, Singapore, Sri Lanka, Tonga, and Thailand. The WHO publishes Dengue Situation Updates for the Western Pacific Region in 2025.

The Centre for Health Protection (CHP) in Hong Kong reported 7 imported Dengue Fever cases as of March 20, 2025. In 2024, 161 were imported (75 from Mainland China) and five local cases. In 2023, 62 imported cases of DF were recorded.

As of February 15, 2025, the Republic of the Philippines had reported 43,732 dengue cases, which is 56% higher than the 27,995 cases recorded in the same period in 2024. The Quezon City Government in the Philippines, through the City Health Department (QCHD), has declared a dengue outbreak. From January 1 to March 9, 2025, the City Epidemiology and Surveillance Division of QCHD recorded 3,608 dengue cases, nearly 300% higher than last year. In 2024, the Republic of the Philippines Negros Occidental had 6,799 dengue cases and 22 dengue-related deaths in 2024.

In September 2024, the WHO reported that dengue outbreaks in Indonesia (E000099) are at level 4. Dengue virus (DENV) infection is a significant cause of acute febrile illness in Indonesia, a DENV-endemic region that has experienced a 700-fold increase in incidence over the past 45 years. As of July 2024, 149,866 confirmed cases of Dengue and 884 deaths had been reported from 465 districts across 38 provinces of Indonesia in 2024.

Dengue Outbreaks in the  Eastern Mediterranean Region

Dengue and severe dengue epidemics were first reported in the WHO's Eastern Mediterranean Region in 1998. Since then, outbreaks have occurred in all nine endemic countries: Afghanistan, Djibouti, Egypt, Oman, Pakistan, Saudi Arabia, Somalia, Sudan, and Yemen. On July 17, 2024, the WHO reported 12 autochthonous (local) cases of Dengue documented in Iran. In August 2024, dengue screening at the Iranian border was launched.

Dengue Outbreaks in Europe

In Europe, dengue viruses, transmitted by Aedes albopictus mosquitoes, are primarily associated with infections acquired in endemic countries. Local transmission remains rare, with only sporadic or small-scale outbreaks documented. In 2024, the ECDC reported locally acquired dengue cases in France, Italy, and Spain. In 2023, 130 locally acquired dengue cases were reported in the EU/EEA. Imported dengue cases in Europe increased from 1,572 in 2022 to about 4,900 in 2023.

In 2024, France reported 82 locally transmitted dengue fever cases and over 4,042 imported cases. In 2023, France reported nine dengue outbreaks that produced 45 autochthonous infections. In 2022, France reported 65 locally acquired dengue cases.

The Italian National Public Health Authority reported 213 locally acquired dengue cases in 2024 and 82 locally acquired dengue cases in 2023. In Fano, a small coastal city in the Marche Region, Eurosurveillance reported 138 confirmed and 61 probable cases of DENV-2 were reported by October 28, 2024. Travel-related dengue cases have reached 472 in 2024. Non-travel-associated dengue cases have been reported in Italy since 2020 (10 cases).

In February 2025, the Autonomous Region of Madeira (Portugal) reported entomological investigations confirming Dengue's presence in mosquitoes captured on Madeira. Two people were infected. The dengue outbreak in 2012 impacted about 1,000 residents.

Spain reported eight locally acquired dengue cases in the Camp de Tarragona area of the Catalonia region in 2024, and the Catalonia region reported three local cases in 2023.

Dengue Outbreaks in India

As of September 2024, dengue cases in India are increasing, especially in Karnataka, Kerala, and Tamil Nadu. They generally peak in October. According to data from the National Centre for Vector-Borne Diseases Control Program, India reported 289,235 dengue cases and 485 related deaths in 2023. In the Democratic Socialist Republic of Sri Lanka, the co-circulation of multiple dengue virus genotypes was reported in October 2024 to be associated with increased cases.

Dengue United Kingdom

As of December 2024, the UKHSA reported 459 travel-related dengue cases had been reported in England, 11 in Wales, and 4 in Northern Ireland. The most significant proportion of English cases (40%) was reported in London. This data represents a 201% increase compared to the same period in 2023, which saw 157 cases. In 2024, travel history was known for 441 out of 473 cases in the U.K., with the majority of these reporting travel to Barbados (125, 28%), followed by Brazil (67, 15%), and Indonesia (54, 12%).

Dengue Virus-Carrying Mosquito

Mosquito bites cause more human suffering than any other organism. The spread of Dengue throughout the world can be directly attributed to the proliferation and adaptation of these mosquitoes. In the U.S., there are 176 species. A recent study published by the Royal Society indicates that dengue-carrying mosquitoes are expanding their range by an average of 6.5 meters of elevation and have moved polewards by 4.7 km annually.

Dengue Disease

Dengue is a disease caused by a virus spread through mosquito bites. It can take up to two weeks to develop, but the illness generally lasts less than a week. Without treatment, severe Dengue can become fatal. New research has identified pre-existing anti-DENV IgG antibodies as responsible for the increased duration of Dengue upon second exposure.

Severe Dengue

 Approximately 5% of Dengue cases can progress rapidly to Severe Dengue, which may involve hypovolemic shock, gastrointestinal or vaginal bleeding requiring transfusion, and end-organ impairment. Furthermore, women infected with Dengue during pregnancy can pass the virus to their fetuses. Promptly initiating intensive supportive therapy can reduce the risk of death among patients with severe Dengue. The extent and duration of viremia often appear to be associated with clinical disease severity. A study published in October 2024 concluded that secondary dengue infections with different dengue virus serotypes have been linked to an increased risk of Severe Dengue after two years. 

Dengue Viruses

There are four Dengue Viruses. A study published in October 2024 concluded that the co-circulation of multiple genotypes is associated with increased cases, highlighting the importance of continuous surveillance.

Dengue Virus Blood Transfusion-Transmission 

Emerging evidence published in November 2024 suggests a potentially concerning route of blood transfusion-transmitted dengue virus (TT-DENV), which poses a critical threat, especially in endemic countries like Brazil. In May 2024, a RESEARCH ARTICLE found that dengue virus transmission was a risk in blood donation in Thailand. In March 2016, Transfusion-Transmitted Dengue and Associated Clinical Symptoms During the 2012 Epidemic in Brazil was published.

Dengue Infection Immune-Mediated Enhancement

In this study, published on October 31, 2024, researchers demonstrate that the expression of a DENV-specific B cell receptor (BCR) renders cells highly susceptible to DENV infection, with the infection-enhancing activity of the membrane-restricted BCR correlating with the ADE potential of the IgG version of the antibody. In addition, they observed that the frequency of DENV-infectible B cells increases in previously flavivirus-naïve volunteers after a primary DENV infection. These findings suggest that BCR-dependent infection of B cells is a novel mechanism for immune-mediated enhancement of DENV infection. This observation indicates that BCR-dependent infection of DENV-specific B cells may be a complementary mechanism of immune-mediated enhancement of DENV infection that expands upon and complements existing models of antibody-dependent enhancement.

Dengue Outbreak Discrepancy Research 2024

In October 2024, a study published by The Lancet Infectious Diseases provided novel insights into serotype-specific epidemiological patterns and disease outcomes of primary DENV infections by revealing the hidden contribution of inapparent infections. This indicates that case surveillance skews the perceived epidemiological footprint of Dengue's four viruses. On October 25, 2024, these researchers wrote, 'While inapparent infections are often overlooked and do not require immediate medical attention, we have assumed that they account for up to 88% of all dengue virus (DENV) transmission events. A study published in May 2024 revealed substantial discrepancies between estimates and reported dengue cases. A study published by the journal Nature in January 2024 uncovered variations in antibody composition that contribute to miscounting primary and secondary prior infection.

Dengue Virus in Pregnant Women

The CDC confirms that a pregnant woman already infected with Dengue can pass the virus to her child during pregnancy, and there has been one documented report of Dengue spread through breast milk. A study published in the American Economic Journal: Applied Economics in April 2024 confirmed robust evidence for the negative effect of dengue infections on birth weight and documented increases in children's hospitalizations and medical expenditures for up to three years after birth.

Dengue and Zika Virus

A study published in the journal Science Translational Medicine on May 29, 2024, found that primary ZIKV infection increased the risk of disease caused by DENV3 and DENV4 but not DENV1. This finding was also factual for tertiary infections when individuals were previously infected with DENV and ZIKV, but not when previously infected with ZIKV and DENV.

Dengue Vaccines

Information on dengue vaccines (Qdenga) and vaccine candidates can be found at Vax-Before-Travel.