Zika and Dengue Worldwide: 2025 update and travel advisory
- Paul Aage Hegvik
- Mar 27
- 6 min read
Zika and dengue viruses, both transmitted by the Aedes aegypti mosquito, remain major public health threats, particularly in tropical and subtropical regions.
Dengue is widespread in the Americas, Southeast Asia, Africa, and the Pacific Islands, with peak transmission during the rainy season. Severe cases of dengue can lead to hemorrhagic fever, organ failure, and death if not treated promptly.
Zika virus remains a serious concern, particularly in Brazil, which is leading the Americas in 2025 with over 2,500 reported cases, primarily in Mato Grosso, São Paulo, Acre, and Rio Grande do Norte. Argentina has also reported 433 cases this year, while Puerto Rico had 19 cases in 2024. Although no cases have been reported in the United States in 2025, Zika remains a persistent threat in regions with active outbreaks.
Dengue overview
Dengue, caused by the dengue virus transmitted through the Aedes aegypti mosquito, is widespread across tropical and subtropical regions. According to the the US-based Centers for Disease Control and Prevention (CDC), dengue risk is highest in:
The Americas: Particularly in Brazil, Mexico, and Puerto Rico.
Southeast Asia: Including Thailand, Indonesia, and the Philippines.
Africa: Countries like Kenya and Nigeria continue to report cases.
The Pacific Islands: Such as Fiji and Palau.
Dengue outbreaks occur year-round, with peak transmission during the rainy season. Severe cases can lead to dengue hemorrhagic fever, which is life-threatening.
Zika virus update for 2025
The Zika virus, also transmitted by the Aedes aegypti mosquito, remains a concern in the Americas. According to the US-based publication Vax-Before-Travel, Brazil leads Zika cases in 2025, reporting 2,556 cases since the beginning of the year. Most cases have occurred in:
Mato Grosso: A region with significant rainforest coverage.
São Paulo and Acre: Urban and rural areas are affected.
Rio Grande do Norte: A northeastern state where cases have increased.
Argentina reported 433 Zika cases this year, while the United States has had no confirmed cases in 2025. However, Puerto Rico reported 19 cases in 2024.
Risks and concerns
Pregnant women are at high risk due to the link between Zika and microcephaly in newborns.
Travelers visiting outbreak areas should be cautious, as Zika and dengue co-infections have been reported.
Travel tips and advice
Use insect repellents Apply DEET-based repellents on exposed skin and clothing.
Wear protective clothing Long-sleeved shirts and long pants reduce exposure to mosquito bites.
Use mosquito nets Especially in areas where air conditioning or sealed windows are not available.
Stay indoors during peak hours Mosquitoes that transmit dengue and Zika are most active during early morning and late afternoon.
Consider vaccination Dengue vaccines like Dengvaxia are available in certain countries, but there is no approved vaccine for Zika yet.
Pregnant travelers Avoid travel to Zika-endemic areas or consult with healthcare providers before making travel decisions.
Be vigilant after travel Monitor for symptoms such as fever, rash, joint pain, or eye redness and seek medical advice if needed.
Dengue cases in 2024
Dengue continued to spread widely in 2024, with large outbreaks reported in multiple regions:
The Americas Over 4.5 million dengue cases were reported across Latin America and the Caribbean. Brazil alone recorded more than 2.9 million cases, accounting for the majority of cases in the region.
Southeast Asia Countries like the Philippines, Thailand, and Indonesia reported a significant increase in cases, with approximately 1 million cases recorded collectively.
Africa Dengue outbreaks in Kenya, Sudan, and other African countries contributed to a growing caseload, though exact numbers were not fully documented.
Zika cases in 2024
Zika virus cases in 2024 were relatively lower than during the initial outbreaks of 2015-2016 but showed a resurgence in some regions:
Brazil: Reported 1,328 confirmed Zika cases in 2024, with the highest concentration in northeastern states.
Puerto Rico: Recorded 19 cases of Zika in 2024.
Other Latin American Countries: Sporadic cases were reported in countries such as Colombia and Mexico, although numbers were not as high as Brazil.
With the rise of Zika cases in Brazil and persistent dengue risks globally, travelers need to take precautions when visiting high-risk regions. While dengue vaccines provide some protection, the lack of a Zika vaccine makes preventive measures essential.
Key facts about Zika and Dengue
Dengue facts
Transmission Dengue is caused by the dengue virus (DENV) and is transmitted primarily by the Aedes aegypti mosquito, which bites during the daytime.
Global Spread Dengue is endemic in over 100 countries, including the Americas, Southeast Asia, Africa, and the Pacific Islands.
Four virus types There are four dengue virus serotypes (DENV-1, DENV-2, DENV-3, and DENV-4). Infection with one type provides lifelong immunity to that type but only short-term immunity to the others.
Severe forms Severe dengue, also known as dengue hemorrhagic fever, can cause internal bleeding, organ damage, and death if not treated.
Symptoms: Dengue symptoms include:
High fever
Severe headaches
Joint and muscle pain (often called "breakbone fever")
Skin rash
Bleeding gums or nose in severe cases
Vaccine availability Dengvaxia, the first dengue vaccine, is available but only recommended for individuals with prior dengue infection.
Annual cases Dengue infects an estimated 390 million people annually, with about 100 million cases showing clinical symptoms. Source: study published by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC). Global Death Toll Dengue causes approximately 20,000 to 25,000 deaths annually, primarily among children and individuals with severe dengue (dengue hemorrhagic fever or dengue shock syndrome).
Case fatality rate: The case fatality rate for severe dengue ranges between 1% and 5% but can reach up to 15% without proper medical intervention.
Zika facts
Transmission Zika is caused by the Zika virus and is transmitted by Aedes mosquitoes, primarily Aedes aegypti and Aedes albopictus. It can also spread through:
Sexual contact
Blood transfusions
From mother to fetus during pregnancy
Geographic range Zika is mainly found in tropical and subtropical regions, including South America, Central America, the Caribbean, Southeast Asia, and parts of Africa.
Pregnancy risk Zika infection during pregnancy can lead to microcephaly and other congenital abnormalities in newborns.
Symptoms Most Zika cases are mild or asymptomatic, but when present, symptoms may include:
Mild fever
Rash
Joint pain
Conjunctivitis (red eyes)
Muscle pain and headache
Neurological complications Zika has been linked to Guillain-Barré syndrome, a rare condition that affects the nervous system.
No vaccine: There is currently no approved vaccine or specific treatment for Zika, making prevention essential.
Past outbreaks The largest recorded Zika outbreak occurred in 2015-2016, with over 1.5 million cases reported in Brazil alone.
Low Mortality Rate Zika virus itself rarely causes death. Most infections are mild or asymptomatic.
Pregnancy Risks While direct fatalities from Zika are rare, the virus poses a severe risk to unborn children. It can cause microcephaly and other congenital disorders, leading to lifelong disabilities.
Key differences
Dengue: More likely to cause severe illness and death, but vaccines are available.
Zika: Less severe in most cases, but poses a higher risk of congenital birth defects.
Average price of Dengue vaccine Worldwide (2025)
The main dengue vaccine currently available is Dengvaxia (CYD-TDV), developed by Sanofi Pasteur. Other vaccines like Qdenga (TAK-003) by Takeda are being introduced in various countries.
Average prices by region
United States:
Dengvaxia: Approx. $200–$250 per dose.
Three doses are required, making the total cost around $600–$750.
Qdenga is not yet widely available in the U.S.
Europe:
Qdenga: Recently approved in the EU, priced around €110–€120 per dose.
Total cost for the two-dose regimen is €220–€240.
Southeast Asia:
Dengvaxia: Priced around $20–$40 per dose in countries like the Philippines and Thailand.
Qdenga: Priced slightly higher, at around $60–$70 per dose.
Public immunization programs may offer the vaccine at subsidized rates or for free.
Latin America:
Dengvaxia: Priced at $50–$70 per dose in Brazil, Mexico, and Colombia.
National vaccination programs may provide the vaccine free of charge to high-risk populations.
India:
Qdenga: Expected to be available in 2025, with an estimated price of around ₹3,000–₹4,000 per dose ($35–$50).
Vaccine considerations
Dengvaxia: Approved for use in individuals aged 9–45 who have had a previous dengue infection. It is not recommended for individuals without prior dengue exposure due to the risk of severe dengue.
Qdenga: Approved in several countries with a broader range of eligibility, even for those without prior dengue infection.
Pro Tip: Travelers visiting dengue-endemic regions should check local availability and pricing, as vaccines may be subsidized or offered through public health programs.
Both viruses are spread by the same mosquito species, making vector control and personal protection essential for prevention.
