## Dengue Fever: Persistent Threat in the Pacific The Pacific region continues to navigate a complex landscape of infectious diseases, with dengue fever remaining a significant public health challenge in several nations as of mid-July 2026. This mosquito-borne illness, caused by the dengue virus, is transmitted to humans primarily through the bite of infected *Aedes aegypti* and *Aedes albopictus* mosquitoes, which thrive in tropical and subtropical climates. Dengue presents with symptoms such as high fever, severe headache, pain behind the eyes, muscle and joint pain, and rash. While most cases are mild, severe dengue can lead to plasma leakage, severe bleeding, or organ impairment, potentially being fatal without proper medical care. In **New Caledonia**, the dengue epidemic appears to be entering a declining phase, a common trend with the onset of cooler weather which typically slows mosquito activity. Since January 1, 2026, over 2,181 cases have been reported, with the vast majority (1,982) being locally acquired. Dengue Serotype 1 (DENV-1) is the sole circulating strain. Public health officials note that the median age of those affected is 29 years, with teenagers in school settings showing the highest incidence. Encouragingly, areas like Grand Nouméa, where the World Mosquito Program has released *Wolbachia*-carrying mosquitoes to reduce dengue transmission, are showing significantly lower weekly incidence rates compared to other parts of the territory. This promising strategy demonstrates the potential for innovative vector control methods. Despite the declining trend, a blue alert remains in effect, underscoring the need for continued monitoring and public awareness. Residents are advised to seek prompt medical attention for symptoms like fever, headache, or muscle pain, and to avoid aspirin or ibuprofen if dengue is suspected, as these can increase bleeding risk. Meanwhile, **Vanuatu** is grappling with an ongoing dengue outbreak on South-West Efate Island. As of EpiWeek 27, 38 laboratory-confirmed cases have been recorded, with the outbreak showing a widening geographic spread beyond its initial concentration. The alert threshold of four cases per week continues to be exceeded, leading to a red alert — indicating a higher level of concern and active response. DENV-1 has also been confirmed as the circulating serotype here. Response efforts are focused on immediate case investigation, controlling mosquito populations, and reducing breeding sites in affected communities. Understanding the dynamics of dengue transmission is crucial for these efforts, as even a small amount of stagnant water can serve as a mosquito breeding ground. Hawaii and New Zealand have also reported travel-related dengue cases, emphasizing the global nature of this disease. While dengue is not endemic in Hawaii, and cases remain limited to travelers, these instances highlight the importance of international surveillance and personal protective measures when visiting dengue-prone regions. ## Whooping Cough: Shifting Landscapes of an Old Foe Pertussis, commonly known as whooping cough, is a highly contagious respiratory infection caused by the bacterium *Bordetella pertussis*. It is particularly dangerous for infants and young children, often leading to severe coughing fits, difficulty breathing, and potentially serious complications like pneumonia, seizures, or even death. Vaccination is the most effective way to prevent pertussis, though booster shots are often recommended for adults as immunity can wane over time. **New Zealand** continues to experience a national pertussis epidemic, initially declared in November 2024. While the number of new cases (42 in the week ending July 3, 2026) shows a slight decrease from the previous week, the cumulative total for 2026 has already surpassed 1,000 cases. A blue alert remains active, signaling continued vigilance. Public health authorities stress the importance of vaccination for all eligible individuals, especially pregnant women (to pass on immunity to newborns) and those in close contact with infants, to create a protective barrier around the most vulnerable. In contrast, **Vanuatu** has achieved a significant public health milestone by officially declaring its pertussis outbreak over. Since EpiWeek 23, no new cases have been reported, marking six consecutive weeks without evidence of ongoing transmission. This declaration follows a period where the cumulative total reached 833 cases, with a concerning seven pertussis-associated deaths, primarily in young children and infants. The outbreak highlighted critical gaps in vaccination coverage, with nearly half of affected individuals having no known vaccination status or being unvaccinated. The successful containment and cessation of the outbreak underscore the effectiveness of sustained public health interventions, including enhanced surveillance, case management, and targeted vaccination campaigns. The removal of the blue alert signifies a return to routine surveillance, but authorities remain prepared for any future re-emergence. ## Avian Influenza H5N1: Human and Wildlife Concerns Highly pathogenic avian influenza A(H5N1), commonly known as bird flu, continues to pose a significant global health concern due to its potential to jump from birds to humans and its high fatality rate in human cases. While primarily an animal disease, human infections are severe and typically occur through direct or close contact with infected poultry or contaminated environments. **Cambodia** has reported its fifth human H5N1 case of 2026, involving a nine-month-old girl from Phnom Penh. This case underscores the ongoing risk of zoonotic transmission in regions where the virus circulates in bird populations. Cambodian authorities are actively investigating the source of infection and tracing contacts to prevent further spread. The historical data from Cambodia reveals a concerning trend: since the re-emergence of human H5N1 infections in February 2023, the country has reported a total of 34 cases with 15 deaths by mid-2026, indicating a substantial fatality rate and the critical need for prompt medical care and robust public health responses. Preventing human infections relies heavily on robust surveillance in animal populations, rapid response to outbreaks in poultry, and public education on safe poultry handling practices. A new and significant development in the region is the first detection of globally circulating H5N1 clade 2.3.4.4b in a native, non-migratory bird in **Australia**. This finding in a greater crested tern in South Australia marks a new phase of the virus's incursion into the continent. Previous detections in Australia had been limited to migratory seabirds arriving from subantarctic regions. The concern with H5N1 establishing itself in resident wildlife populations is twofold: it creates a permanent reservoir for the virus, increasing the risk of spillover into poultry and other animals, and potentially, to humans. While Australian authorities maintain that the risk to human health remains low, they have activated enhanced surveillance and are closely monitoring the situation. This event serves as a stark reminder for the entire Pacific region to maintain heightened vigilance and robust surveillance systems for avian influenza in both domestic and wild bird populations, considering the interconnectedness of migratory bird routes. ## Ciguatera Fish Poisoning: A Focus on Food Safety **Vanuatu** continues to monitor cases of ciguatera fish poisoning (CFP), a type of foodborne illness caused by eating reef fish that have accumulated ciguatoxins. These toxins are produced by certain microalgae (dinoflagellates) found in tropical and subtropical waters, which are then consumed by herbivorous fish, and subsequently by carnivorous fish higher up the food chain. Humans become ill after consuming these contaminated fish. Symptoms can be diverse, including gastrointestinal issues (nausea, vomiting, diarrhea), neurological symptoms (numbness, tingling, temperature reversal), and cardiovascular problems (low blood pressure, slow heart rate). Symptoms can be long-lasting and severe in some cases. As of EpiWeek 27, Vanuatu has recorded 214 cases since the start of the year, with Efate accounting for the largest proportion. The good news is that activity has remained below the alert threshold since EpiWeek 24, indicating a declining trend in cases. Most affected individuals are males aged 15-34 years, and cases have been linked to various reef fish species. Health authorities are actively investigating new cases to identify high-risk fish species and fishing areas. Public health messaging is crucial here, focusing on promoting safe fish consumption practices, which includes knowing which fish species are more likely to carry toxins in certain areas, and seeking early medical care if symptoms develop. ## Regional Vigilance and Public Health Action The diverse health alerts across the Pacific region highlight the continuous need for strong public health surveillance and rapid response mechanisms. From vector-borne diseases like dengue, influenced by climate and environmental factors, to vaccine-preventable diseases like pertussis, where vaccination coverage is key, and zoonotic threats like avian influenza, the region faces multiple challenges. The coordinated efforts of national health ministries, regional bodies like the Pacific Community (SPC), and international partners are vital. Understanding how diseases spread, implementing effective prevention strategies (like mosquito control, vaccination campaigns, and food safety guidelines), and ensuring timely access to medical care are paramount. Public awareness campaigns empower communities to take preventative actions and recognize symptoms early, which is crucial for disease control. The shift in avian influenza in Australia, from migratory to resident birds, serves as a poignant reminder that pathogen evolution and ecological changes require constant adaptation and strengthening of public health defenses across borders. Continuous investment in surveillance, laboratory capacity, and public health workforce development will be essential to protect the health and well-being of Pacific populations.