Regular updates on epidemic and emerging diseases are crucial for public health, particularly in regions like the Pacific, which are highly susceptible to climate-sensitive infections and communicable diseases. As of late May 2026, health agencies are tracking various health challenges across several nations, emphasizing the need for robust surveillance, prompt public health responses, and community engagement. ## Dengue Fever: A Widespread Concern with Regional Success Stories Dengue fever, a mosquito-borne illness, continues to be a significant health concern across many Pacific island nations. The good news comes from the **Cook Islands**, which proudly declared itself dengue-free on May 25, 2026. This success follows a period of no new cases since April 28, 2026, meeting the criteria for officially ending the DENV-1 and DENV-2 outbreak. Their effective 'Operation Namu26' and continued surveillance highlight the impact of coordinated public health efforts. However, the fight against dengue continues elsewhere. **Kiribati** has been grappling with a persistent outbreak since April 2025, with over 535 confirmed and 1,583 suspected cases reported. Transmission, involving both DENV-1 and DENV-2 serotypes, is concentrated in South Tarawa, leading to 68 hospitalizations and one recorded death. Similarly, **New Caledonia** is experiencing an ongoing DENV-1 driven outbreak, with 1,837 cases reported in 2026, fuelled by conditions favorable for mosquito breeding and population movement. Health authorities are intensifying vector control and promoting early medical care. **Samoa** also reports continued dengue transmission with DENV-1 and DENV-2 co-circulation, noting 141 new cases in a recent week, primarily affecting children under 15 years. Since January 2025, the nation has seen over 19,000 clinically diagnosed cases and nine related deaths, underscoring the severity of the situation. **Tonga** is managing an ongoing DENV-2 outbreak, with 66 confirmed cases, mainly among young males in Tongatapu, and two individuals currently hospitalized. All these nations are actively engaged in community awareness campaigns and mosquito control to limit further spread. Beyond these active outbreaks, other regions are under close watch. **Kosrae State in the Federated States of Micronesia** is monitoring dengue activity with three recent cases, maintaining surveillance and vector control. **Vanuatu** has reported eight cases on Efate Island, mostly linked to travel, prompting heightened surveillance despite not reaching outbreak thresholds. Even **New Zealand** has reported two imported dengue cases, underscoring the regional interconnectedness and the importance of traveler precautions. Dengue fever is caused by four distinct serotypes of the dengue virus, transmitted primarily by the *Aedes aegypti* mosquito. Symptoms can range from mild fever and body aches to severe dengue, which can lead to plasma leakage, severe bleeding, or organ impairment, potentially fatal if not managed promptly. Prevention largely relies on controlling mosquito populations by eliminating breeding sites (stagnant water) and personal protection like repellents and protective clothing. Early diagnosis and supportive care are critical for managing cases and preventing severe outcomes. ## Pertussis (Whooping Cough): New Zealand's Lingering Epidemic **New Zealand** continues to face a nationwide epidemic of pertussis, commonly known as whooping cough. As of mid-May 2026, 48 new cases were reported in one week, contributing to a cumulative total of 734 cases for the year. This highly contagious respiratory infection remains a significant public health challenge for the country. Pertussis is caused by the *Bordetella pertussis* bacterium and is characterized by severe, uncontrolled coughing fits that often end with a distinctive 'whooping' sound. It is particularly dangerous for infants and young children, who can develop serious complications like pneumonia, brain damage, or even death. The disease spreads easily through airborne droplets when an infected person coughs or sneezes. Vaccination is the most effective way to prevent pertussis, with booster shots recommended for adolescents and adults, especially those in contact with infants, to maintain immunity and protect vulnerable populations. ## Diphtheria's Resurgence: An Australian Concern **Australia** has observed a notable increase in diphtheria activity since late 2025, reporting 221 confirmed cases in 2026 as of mid-May. This represents a substantial rise compared to previous years, particularly concentrated in the Northern Territory and Western Australia, affecting Aboriginal and Torres Strait Islander communities in remote areas. Cases include both cutaneous (skin) and respiratory forms, with one death under investigation. Diphtheria is a serious bacterial infection caused by *Corynebacterium diphtheriae*, which can produce a toxin affecting the throat, nose, and skin. The toxin can lead to severe complications, including heart damage, nerve damage, and breathing difficulties. Like pertussis, diphtheria is highly preventable through vaccination. The resurgence highlights the critical importance of maintaining high vaccination coverage within communities, as gaps in immunity can allow these once-controlled diseases to re-emerge. ## Ebola Virus Disease: International Emergency in DRC and Uganda An outbreak of Ebola disease, specifically caused by the less common Bundibugyo virus, in the **Democratic Republic of Congo (DRC) and Uganda** has been declared a Public Health Emergency of International Concern by the WHO on May 16, 2026. As of late May, 85 confirmed cases and 10 confirmed deaths have been reported across both countries, including imported cases in Uganda. The outbreak in DRC spans Ituri, North Kivu, and South Kivu provinces, complicated by high population mobility, humanitarian challenges, and difficulties with contact tracing and isolation. Ebola virus disease is a severe, often fatal illness in humans. The Bundibugyo virus strain, while distinct from the more commonly known Zaire strain, causes similar symptoms including fever, severe headache, muscle pain, fatigue, diarrhea, vomiting, and unexplained bleeding or bruising. Currently, there are no licensed vaccines or specific treatments available for Bundibugyo virus. Response efforts are focused on intensive surveillance, meticulous contact tracing, stringent infection prevention and control measures, careful case management, safe and dignified burials, and cross-border coordination to contain the spread. The WHO has not recommended travel or border closures at this time. ## Murray Valley Encephalitis: A Seasonal Threat in Northern Australia The **Northern Territory of Australia** has reported recent detections of Murray Valley encephalitis (MVE) virus, including two confirmed cases in Alice Springs, both of whom tragically died. The virus has also been found in mosquitoes in the Greater Darwin region. Increased rainfall during the wet season contributes to larger mosquito populations, elevating the risk of this rare but potentially severe mosquito-borne infection. Murray Valley encephalitis is a viral disease transmitted by mosquitoes that can cause inflammation of the brain, leading to severe neurological symptoms. While most infected people experience no symptoms or mild illness, some can develop fever, headache, neck stiffness, confusion, seizures, or coma. There is no specific treatment for MVE, so prevention is key. Public health authorities are enhancing mosquito surveillance and control activities. The public is advised to take precautions against mosquito bites, especially during the seasonal risk period from February to July, by using repellents, wearing protective clothing, and ensuring screens on windows and doors. These ongoing health alerts underscore the dynamic nature of infectious diseases and the continuous need for vigilance, effective public health interventions, and international cooperation to safeguard community health across the Pacific and beyond.