The count of dengue cases in the Americas has surpassed three million this year. This places 2023 as the second-highest annual incidence of the disease since 1980, when the Pan American Health Organization commenced data collection on case numbers.
The virus is transmitted by mosquitoes carrying the infection, leading to illness in about 25% of those infected. Symptoms can range from mild fever to severe shock or even death. A recent article in JAMA emphasizes the necessity of better virus control in U.S. territories, as highlighted by researchers from the Centers for Disease Control and Prevention in Puerto Rico.
You can also read: What to Know About the Deadly Mosquito-Borne Dengue
Over the past two decades, dengue outbreaks have taken place in Texas, Hawaii, and now southern Florida. These incidents underscore the conditions for the local transmission of the virus within the U.S. This calls for increased vigilance among healthcare professionals regarding potential cases among returning travelers and the resurgence threat of dengue in the country in the years ahead.
Situation at a glance
From the beginning of 2023, substantial dengue outbreaks have been documented in the WHO Region of the Americas. Approximately three million suspected and confirmed dengue cases have been reported this year, surpassing the 2.8 million cases recorded for the entire year of 2022. Out of the total dengue cases reported until July 1, 2023 (amounting to 2,997,097 cases), 45% were confirmed through laboratory testing, and 0.13% were classified as severe dengue cases. Brazil, Peru, and Bolivia have reported the highest number of dengue cases in 2023. Within the same period, there were 1302 reported deaths in the Region, resulting in a Case Fatality Rate (CFR) of 0.04%.
To combat these outbreaks, the World Health Organization (WHO) is actively collaborating with Member States to enhance healthcare systems and surveillance capabilities through the Integrated Management Strategy for the Prevention and Control of Arboviral Diseases (IMS-Arbovirus).
Due to the widespread presence of Aedes spp. mosquitoes, particularly Aedes aegypti, the risk of dengue is assessed as high at the regional level. This risk is attributed to the ongoing potential for severe disease and fatalities, as well as the expansion of transmission areas beyond historical boundaries. This expansion raises concerns about public awareness, including risk groups and healthcare professionals, being informed about warning signs.
Presently, based on available information, WHO does not recommend implementing travel or trade restrictions for countries in the Americas currently grappling with dengue epidemics.
Figure 1. Number of dengue cases in 2022, 2023 (up to EW 26) and average of the last 5 years in the Region of the Americas
Description of the situation
Dengue, the arbovirus responsible for the highest caseload in the Region of the Americas, undergoes cyclical epidemics every 3 to 5 years. In the first half of 2023, significant dengue outbreaks surfaced in South America. From epidemiological week (EW) 1 to EW 26 of 2023 (ending on July 1), the Region of the Americas documented a total of 2,997,097 dengue cases, including 1302 deaths, yielding a Case Fatality Rate (CFR) of 0.04%. The cumulative incidence rate was 305 cases per 100,000 population. Among these cases until EW 26 of 2023, 1,348,234 (45%) were confirmed via laboratory testing, while 3907 (0.13%) were categorized as severe dengue cases. Brazil reported the highest number of dengue cases at 2,376,522, followed by Peru with 188,326 cases, and Bolivia with 133,779 cases.
The most elevated cumulative incidence rates were observed in the Southern Cone with 862 cases per 100,000 inhabitants, the Andean Subregion with 268 cases per 100,000 inhabitants, and the Central American Isthmus and Mexico with 59 cases per 100,000 inhabitants.
The highest occurrences of severe dengue cases were noted in Brazil with 1249 cases, Peru with 701 cases, Colombia with 683 cases, Bolivia with 591 cases, and Mexico with 141 cases.
All four dengue virus serotypes (DENV1, DENV2, DENV3, and DENV4) exist within the Region of the Americas. Up to EW 26 of 2023 (ending on July 1), Brazil, Colombia, Costa Rica, Guatemala, Honduras, Mexico, and Venezuela had simultaneous circulation of all four serotypes. Argentina, Panama, Peru, and Puerto Rico had DENV1, DENV2, and DENV3 serotypes circulating, while Nicaragua had DENV1, DENV3, and DENV4 serotypes.
In 2022, the Region of the Americas reported 2,811,433 dengue cases, marking the third-highest year on record, trailing only 2016 and 2019. The latter recorded the highest historical dengue cases with over 3.1 million cases for the Region of the Americas, encompassing 28,203 severe cases and 1823 deaths.
Between June 12 and July 1, 2023, some countries in the Southern Cone and the Andean subregion have witnessed a decrease in cases due to various factors, including control measures, changing temperatures, and climate shifts, primarily in the Southern Cone. Additionally, a lag in data reporting from certain Central American and Caribbean countries has contributed to the decline in cases, as depicted by the descending trend observed in the epidemiological curve below.
WHO advice
While most dengue cases tend to be mild, the risk of severe dengue rises with successive infections by multiple serotypes. This heightened risk encompasses conditions such as shock, respiratory distress due to plasma leakage, significant bleeding, organ dysfunction, and even fatalities. Hence, it is imperative for Americas’ Member States to remain vigilant and prepared, ready to escalate efforts in preventing, swiftly detecting, diagnosing, and controlling arboviral diseases. This includes educating healthcare practitioners on case identification, potential complications, risk groups for severe illness, apt clinical management, and continued case monitoring to avert future fatalities.
Anticipating an upsurge in dengue cases during the latter half of 2023, proactive measures such as focused integrated vector surveillance, monitoring insecticide resistance in dengue vectors, and implementing control strategies can substantially curtail transmission rates. As a general precaution, the World Health Organization advises the public to guard against mosquito bites, employing repellents when needed. The period of highest dengue transmission risk typically occurs during daylight and early evening hours.
Overview by selected countries
While dengue is prevalent in numerous South American, Central American, and Caribbean nations, the ongoing period has witnessed a surge in cases surpassing the average recorded over the past five years, extending beyond historical transmission zones. The following presents a synopsis of the dengue epidemiological status in the most impacted countries within the Americas region.
However, vaccines and mosquito modification could help reduce dengue. Meanwhile, ‘there is new reason for hope’ because of better surveillance systems and physician education that has already reduced dengue deaths, researchers write.
Experts hope, combining techniques may reduce dengue even further. For now, dengue continues to put people in U.S. territories at risk.
