A bold warning about unseen risks: dengue can appear where least expected, even in arid resorts that seem inhospitable to the virus.
But here’s where it gets controversial: four travelers returning to Israel from Sharm El-Sheikh in the Sinai Peninsula during spring and early summer 2024 were confirmed to have dengue virus serotype 2 (DENV-2), signaling local transmission in a region previously regarded as unsuitable for the primary mosquito vectors. This finding challenges assumptions about where dengue can spread and persist, raising urgent questions for regional surveillance and public health preparedness.
Summary of cases and context
- Four travelers who visited Sharm El-Sheikh, a desert resort city in South Sinai, Egypt, between April and June 2024 developed dengue fever. The cases were independent of one another, with no overlapping travel dates and lodging destinations separated by 3 to 25 kilometers.
- Common dengue symptoms were present in all patients, including fever, headache, muscle and joint pains, and rash. All required hospital admission for supportive care and recovered successfully. One patient showed signs of meningeal irritation, but cerebrospinal fluid tests were normal; dengue-2 RNA was detected in that patient’s sample by quantitative real-time PCR (cycle threshold around 32.5). Specimens were collected within one week of symptom onset. Serum testing confirmed DENV-2 by multiplex real-time PCR, with some cases also testing positive for nonstructural protein 1 antigen and IgM/IgG antibodies.
Genomic investigation and origins
- Whole-genome sequencing of the DENV-2 samples revealed that the four Israeli cases clustered within the Cosmopolitan genotype. All three sequences formed a tight cluster, sharing a recent common ancestor and differing from the nearest global strain by 32 mutations.
- The closest relatives were strains from Pakistan. A publicly available sequence from the United Arab Emirates in 2023, geographically near Sinai, clustered in a separate Cosmopolitan lineage alongside strains from China, India, and Bangladesh.
- One case (patient 4) could not be used for genome analysis due to high cycle threshold values, but the remaining three provided strong evidence of a shared viral origin.
Methods at a glance
- DENV-2 genomes were captured using specialized whole-genome primers and prepared for sequencing with Nextera-XT, then run on an Illumina platform. Consensus genomes were built by aligning reads to the DENV-2 reference genome NC_001474.2 and were deposited in GenBank.
- The study received ethical approval from the Sheba Medical Center Institutional Review Board (approval no. SMC-6190-19).
Interpretation and implications
- The clustering of the Israeli cases suggests ongoing local transmission within Sharm El-Sheikh, indicating that dengue-2 can circulate in this region more than previously recognized. The genetic data imply a likely single outbreak source, most closely related to Pakistani strains, with limited recent sequence data from Sinai or nearby regions to precisely map the origin and spread.
- This scenario aligns with broader patterns of dengue spread observed along the Red Sea corridor and in other travel-associated outbreaks, underscoring the role of human movement in introducing and disseminating the virus.
- While Aedes aegypti mosquitoes have expanded in Egypt—particularly along the Red Sea coast—direct entomological data for Sinai are lacking. The observed case clustering in a single resort area suggests possible adaptation to urban microenvironments, even in an arid setting. Regular maritime and air travel may facilitate repeated introductions of Aedes vectors and DENV into the Red Sea region.
Public health takeaways
- The occurrence of these four infections over a three-month period across different locales in Sharm El-Sheikh highlights the need for enhanced vector surveillance and control measures, especially in tourist hubs where visitors can become reservoirs for future spread.
- The genomic findings help fill gaps in regional dengue sequence reporting and contribute to understanding the molecular epidemiology and movement of DENV-2 in the Middle East and adjacent regions.
Author and affiliation notes
- Dr. Zuckerman leads the Bioinformatics and Genomics Center at Israel’s Central Virology Laboratory, with affiliation to Tel Aviv University’s School of Public Health. The team’s work emphasizes genomic surveillance, molecular epidemiology, and bioinformatics applications in studying viral pathogens.
Controversial takeaway and discussion prompts
- If dengue can establish transmission in arid resort regions previously deemed unsuitable for Aedes vectors, should public health policies expand vector surveillance and mosquito-control efforts to more inland or non-traditional settings?
- How should travel-associated dengue findings influence regional collaborations and data-sharing to close gaps in sequence data from under-sampled areas like Sinai and neighboring regions?
- Do these cases warrant re-evaluating risk communication for travelers to seemingly low-risk destinations, given the potential for rapid, covert outbreaks?
Would you like this rewritten piece to emphasize practical travel health tips for visitors to desert resort areas, or to include a concise box that explains dengue transmission and why arid environments can still pose a risk?
