Emerging Disease Alerts in the Pacific: Dengue and More (Jan 2026 Update)

Attachments Download Map (PDF | 597.42 KB) Highlights/updates since the last map was sent on PacNet on 13 January 2026: Dengue Cook Islands: On 22 May 2025, the Cook Islands Ministry of Health declared a dengue outbreak in Rarotonga. As of 19 January 2026, 507 cases were reported, with 434 recovered and 73 still active. Most of the cases are in the 10-19 age group, and no fatalities or severe dengue cases have been reported. Of the 50 samples serotyped, 47 were DENV-1 and 3 were DENV-2, confirming co-circulation. Authorities are conducting peri-focal and block spraying targeting hot spots, risk assessments and clean-up of all islands, urging the public to eliminate mosquito breeding sites, empty water containers, use repellent, mosquito coils and seek medical attention if unwell. The blue alert for DENV-1 and DENV-2 remains in effect. – Source: Cook Islands 2025 Dengue Outbreak Situation Report #77 (19 January 2026) shared with PPHSN Coordinating Body focal point on 20 January 2026. Samoa: As of 4 January 2026, Samoa Ministry of Health has recorded a cumulative total of 16,299 clinically diagnosed dengue cases since January 2025, including 4,717 laboratory-confirmed cases, and seven dengue-related deaths. Children under 15 years account for 74% of the cases, and the circulating serotypes remain predominantly DENV-1 (91%) and DENV-2 (9%). Case numbers increased by 8% compared to the previous EpiWeek, with 40 new clinical cases of which 19 are lab-confirmed. There are no hospital admissions for this EpiWeek 01 (29 December–4 January 2026). The Ministry of Health continues its control measures combined with targeted sensitization of the community and government leaders, and ongoing district and multimedia awareness integrating dengue and measles messaging. A MOH-UNICEF KAP survey shows improved dengue knowledge and risk perception, creating opportunities to promote protective behaviours. The public are recommended to promote environmental clean‑ups to reduce mosquito breeding, use protective clothing, nets and repellents to prevent bites, and if illness occurs, to promptly seek medical care while monitoring household members for symptoms and testing. The blue alert for DENV-1 and DENV-2 remains in effect. – Source: Dengue Fever Outbreak Situation Report in Samoa Issue No. 38, Epi-week 1: 29 December – 4 January 2026 accessed on 20 January 2026. Influenza French Polynesia: In French Polynesia, an outbreak of influenza is ongoing with 438 confirmed cases reported since the start of the outbreak, including 437 Influenza A cases. In the current reporting period, (EpiWeek 02: 5-11 January 2026), twenty-five new Influenza A cases were identified of which twenty-two required hospitalisation including three admitted to intensive care. No additional deaths were reported this week, and the cumulative death toll remains at 10. Influenza A(H3N2) is the predominant subtype. Seasonal flu vaccination is available for target groups at all healthcare facilities and selected pharmacies. A red alert for Influenza A remains in effect. – Source: Bulletin de surveillance sanitaire de Polynésie française n°2 - 2026 shared with PPHSN Coordinating Body focal point on 20 January 2026. Wallis and Futuna: In Wallis, cases of influenza-like illness and emergency department visits have fallen below the alert thresholds, marking the end of the epidemic episode. In Futuna, emergency department visits and influenza-like illness cases remain above the thresholds, but the situation is stable. One hospitalization is currently ongoing in Futuna. The total number of influenza-like illness cases reported between the beginning of December 2025 and 20 January 2026 in Wallis and Futuna stands at 1,209. The red alert for Influenza A remains in effect. – Source: Personal communication with Wallis and Futuna focal point 20 January 2026. Federated States of Micronesia: In the Federated States of Micronesia, the Yap Communicable Disease Report for EpiWeek 49-2025 (1 – 7 December 2025) highlighted a significant surge in influenza-like-illness (ILI) with 136 cases reported, more than double the previous week, which prompted the Yap EpiNet team to declare an influenza outbreak on 08 December 2025. The surge in ILI was detected in the outer islands, namely Woleai Atoll, Lamotrek and Elato. As of 16 January 2026, 3 new ILI cases were reported bringing the cumulative total since 16 November 2025 to 917 cases. The laboratory has confirmed 58 infuenza A cases, including two subtyped as A(H3) and 3 respiratory syncytial virus (RSV) infections. The most affected age group is 0-4 years. While reports are declining on mainland Yap, there are indications of rising ILI cases at sentinel sites in the outer islands with incomplete data from some islands still pending. The red alert for Influenza A remains in effect. – Sources: Yap Communicable Disease Report for Week 49 and State Department of Health Services, Situational Report No. 16 (16 January 2026) shared with PPHSN Coordinating Body focal point on 19 January 2026. New Caledonia: In New Caledonia, since the beginning of 2025, 493 influenza cases have been reported. Two epidemic waves have been observed in 2025: the first between EpiWeeks 51-2024 and 04-2025 (140 cases) and the second, which began in EpiWeek 48-2025, is still ongoing with 274 cases. As of 16 January, the number of cases has been steadily decreasing since EpiWeek 01 with 59 tests in EpiWeek 02 compared to 33 tests in EpiWeek 03. The test positivity rate has also decreased from 27% in EpiWeek 02 to 15% in EpiWeek 03. The trends indicate that the outbreak is in a declining phase. The percentage of respiratory infections recorded through the sentinel surveillance network is also declining and has fallen below the epidemic threshold thus the red alert for Influenza A is changed to a blue alert. – Source: An Update of Alerte DASS Grippe, The Department of Health and Social Affairs (DASS) shared with PPHSN Coordinating Body focal point on 19 January 2026. Influenza-like illness Republic of Marshall Islands: The Republic of Marshall Islands (RMI) Communicable disease weekly report for EpiWeek 01 (29 December – 4 January 2026) highlighted a surge in influenza-like illness (ILI) from EpiWeek 49-2025 with a peak in Week 51, followed by a decrease in case numbers till EpiWeek 01-2026. The trend has remained at a plateau for the current reporting period (EpiWeek 02: 5-11 January 2026). Despite the decrease in case numbers, the epi-curve is still above threshold. The ILI cases were reported from across Majuro and neighbouring islands. Individuals affected are in recovery phase. The aetiology is yet to be determined thus a grey alert for ILI remains in effect. – Source: RMI Communicable Disease Weekly Report for EpiWeek 02 (5 – 11 January 2026) shared with PPHSN Coordinating Body Focal point on 16 January 2026. Measles Australia: In Victoria, a new measles case was reported on 17 January 2026 marking the second case identified in January 2026, with both cases linked to returned travellers from South-East Asia. In New South Wales (NSW), NSW Health has issued an alert on 19 January 2026 for greater western Sydney after a confirmed case who recently returned from Thailand where there are ongoing outbreaks of measles and was infectious while visiting locations in greater western Sydney. Exposure sites have been listed. Individuals who visited the listed exposure sites during the specified dates and times are advised to monitor for symptoms for up to three weeks from the exposure date, seek medical advice if symptoms develop and to check their vaccination status is up to date. For the year 2025, a total of 181 cases has been reported across Australia with recent reports from Victoria, New South Wales, Queensland, South Australia, Tasmania, Western Australia and Northern Territory. Already in 2026, 11 cases have been reported across New South Wales (4), Queensland (5) and Victoria (2). The red alert for measles in Australia remains in effect. – Sources: New measles cases in Victoria 17 January 2026,Measles alert for greater western Sydney 19 January 2026, and National Communicable Diseases Surveillance Dashboard accessed on 20 January 2026. New Zealand: As of the week ending on 19 December 2025, 3 measles cases were reported with no new measles cases reported for 4 weeks thereafter thus the red alert for measles in New Zealand is now removed. – Sources: Personal exchange with New Zealand Institute for Public Health and Forensic Science focal point, New Zealand Health: Measles outbreak update - Wednesday 17 December 2025 and Measles dashboard accessed on 20 January 2026. Pertussis/Whooping cough New Zealand: As of the week ending on 9 January 2026, weekly pertussis cases in New Zealand increased to 51 cases as compared to 38 in previous week ending on 2 January, bringing the total reported cases since the beginning of 2026 to 58. According to the latest report from the New Zealand Institute for Public Health and Forensic Science (PHF Science), 3,861 confirmed, probable and suspect cases have been notified since the start of the national epidemic on 19 October 2024. Of these, 341 cases (9.2%) have required hospitalisation with one reported death. Out of the 323 cases in infants under 1 year, 164 (51.3%) have been hospitalised. The blue alert for pertussis remains in effect. – Sources: Pertussis dashboard and Pertussis report 13 December–9 January 2026 accessed on 20 January 2026. Vanuatu: The Vanuatu Ministry of Health officially declared a Pertussis (Whooping Cough) outbreak on Tanna Island, Tafea Province on 18 August 2025. As of 19 January 2026, 758 cases (730 clinically diagnosed and 28 confirmed cases) have been reported across Tanna, Efate, Erromango and Futuna. The outbreak has resulted in three infant deaths. At present, one case remains hospitalised, while all previously hospitalised cases have been discharged. Most of the cases are reported across all age groups with the highest proportions observed among children aged 2-5 years and persons below 5 years. The red alert for pertussis remains in effect. – Sources: Vanuatu is currently facing an outbreak of pertussis, and Pertussis in Vanuatu Situation Update #10 (19 January 2026) shared on PacNet on 19 January 2026. Other Information: Arbovirus Hawaii: Hawaii’s Department of Health has confirmed one travel-related case each of Zika and dengue virus on Oahu, with no links between the cases or to any prior Hawaii infections. This marks the first Zika case on Oahu in 2026, while the dengue case counts as Hawaii’s 15th dengue case for 2025 based on symptom onset, and no locally acquired transmission has been identified. Health officials have deployed mosquito control and outreach teams and stress that both viruses were only found in travelers, while continuing surveillance and prevention efforts. Source: Zika and dengue cases confirmed on Oahu accessed on 20 January 2026. New Zealand: In New Zealand (NZ) for the surveillance week 02 2026 (10 – 16 January 2026) there were twenty (20) confirmed imported cases of dengue reported with travel history to Cook Islands, one (1) confirmed imported case of dengue with travel history to Samoa and one (1) confirmed imported case of Zika with travel history to Papua New Guinea. Multiple arboviruses are currently circulating in the Pacific Island region and have historically been associated with outbreak activity. Given the known serological cross‑reactivity between dengue and other flaviviruses, it is possible that a proportion of cases reported as dengue may be attributable to other flaviviruses. Case classifications may therefore be subject to change as epidemiological and laboratory investigations continue. Source: NZ Arbovirus Notifications by Country (02: 10/01/2026–16/01/2026) shared with PPHSN Coordinating Body Focal point on 20 January 2026. Japanese Encephalitis Australia: NSW Health is urging communities in southern NSW to protect against mosquito bites following a probable case of Japanese encephalitis (JE) in the Riverina region and detection of the virus in sentinel chickens near Goulburn. JE is a rare but potentially serious mosquito-borne illness with no specific treatment, and vaccination is recommended for people living or working in high-risk areas, with free vaccines available through GPs, Aboriginal health services, and pharmacies. Residents are advised to take preventive measures such as using repellents, wearing protective clothing, and eliminating mosquito breeding sites. Source: Communities across southern NSW urged to protect themselves against mosquito bites accessed on 20 January 2026. Measles Canada: In Canada, for EpiWeek 01 (4 – 10 January 2026) there has been 17 new confirmed measles cases reported by 4 jurisdictions, Alberta, British Columbia, Manitoba and Saskatchewan. Canada lost its measles elimination status in 2025 following sustained transmission, and the current outbreak has resulted in over 5,300 cases nationally since 2024. – Source: Government of Canada Measles and rubella weekly monitoring report Epi-week 1: 28 4–10 January 2026 accessed on 20 January 2026. United States: In the United States, for the year 2025 the CDC reported a total of 2,242 measles cases across 45 U.S. jurisdictions, with 89% of these cases linked to forty-nine outbreaks. As of 13 January 2026, 171 confirmed measles cases reported in the U.S. in 2026. The majority of cases are among unvaccinated individuals (95%), and 1% of the cases have resulted in hospitalization. There have been three confirmed deaths. The 45 jurisdictions that have reported measles cases are: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Jersey, New Mexico, New York City, New York State, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, Wisconsin, and Wyoming. – Source: CDC Measles Cases and Outbreaks Update as of 13 January 2026, accessed on 20 January 2026. Pertussis/Whooping cough Guam: The Guam Department of Public Health and Social Services (DPHSS) has confirmed the first case of pertussis (whooping cough) for 2026 on 8 January and initiated epidemiologic investigation and contact tracing to determine the source of exposure. Pertussis is a highly contagious, vaccine-preventable respiratory illness that can cause severe complications, especially in infants, and DPHSS urges residents to ensure their vaccinations are up to date. Vaccines (DTaP and Tdap) are available at DPHSS health centres, and individuals with flu-like or pertussis symptoms should contact their healthcare provide. Source: Press Release Public Health Alert: First Case of Pertussis Confirmed for 2026 shared on PacNet on 13 January 2026.