Dengue in the Pacific: A Reminder to Keep Influenza on the List
There is a Dengue outbreak in Fiji. The outbreak started this year, with 23,500 suspected cases recorded in the Pacific so far, and 1,900 in Samoa just last week. It is the largest outbreak in a decade, according to the WHO [1].
Dengue is a mosquito-borne illness with no human-to-human transmission. In Australia, outbreaks occur in North and Central Queensland when an imported case is bitten by a local Aedes aegypti mosquito, which then spreads it to others nearby. These outbreaks are limited, and Dengue has never gained endemicity here. Aedes mosquitoes favour urban environments, laying eggs in stagnant water trapped in man-made containers, and they bite during the day.
Patients typically present with sudden malaise, lethargy, fever, and body ache. The headache is often intense, felt behind the eyes. There is muscle and joint pain, loss of appetite, vomiting, diarrhoea, and abdominal pain, sometimes with a rash on the face, neck, or arms. Most cases are mild, but a subset develop coagulopathy and plasma leak. Dengue Haemorrhagic Fever and Dengue Shock Syndrome carry mortality rates of up to 40%.
The case
My patient presented on the Monday, having returned from Fiji on the Saturday. Her symptoms had started suddenly on the Sunday: headache, intense body aches, and a high fever that wasn’t holding against Panadol or Nurofen. She was lethargic, fatiguing easily, and reported many mosquito bites while away, along with awareness of the Dengue outbreak at the time. She was drinking copious water and urinating briskly.
I rang her the next day. Her D-dimer had returned at 0.82 ng/L (reference <0.5). She sounded drained, her voice weak, but was keeping up her fluids with the help of some Maxolon, and her urine remained straw-coloured. The elevated D-dimer raised the possibility of a haemorrhagic fever, so I referred her to the Emergency Department.
She returned a positive result for Influenza.
Not Dengue. Her travel history, the outbreak she’d walked into, and a genuinely abnormal D-dimer made a compelling case for at least ruling out DHF, and I’d make the same referral again. But it’s a useful reminder that overlapping symptom pictures, fever, myalgia, headache, fatigue, don’t declare themselves by story alone. Returned travellers from an outbreak region deserve a broad differential, not just the diagnosis the itinerary suggests.
On severe Dengue, for when it is Dengue
Severe abdominal pain (reflecting hepatic involvement) [2], persistent vomiting, bleeding gums, haematemesis, rapid breathing, fatigue, and restlessness are warning signs of DHF/DSS. This is more common in patients who have had Dengue previously: there are four Dengue serotypes, and a second infection with a different serotype raises the risk of a cytokine-driven severe response [3]. My patient’s Dengue status, retrospectively, was moot, but it’s the reasoning I was working through at the time.
Point-of-care ultrasound is most useful around defervescence, and appears superior to clinical and lab assessment for detecting plasma leakage [4,5]:
- CXR/USS (pleural effusion): the most common sign, typically one day after defervescence
- Abdominal USS (ascites): detectable before and even without haemoconcentration, from two days before to three days after defervescence, and resolves faster than pleural effusion
- FBC (haemoconcentration >20%): 48% sensitive, 83% specific, PPV 70%, NPV 67%
- LFT (hypoproteinaemia): 25% sensitive, 90% specific, PPV 73%, NPV 47%
The bigger picture
The Western Pacific Region has recorded 53,397 Dengue cases this year, against 16,346 at the same point last year, with a case fatality rate of 0.12% [1].
Takeaway: in a returned traveller from an outbreak zone with a fever and a worrying lab result, the outbreak doesn’t get to write the diagnosis for you. Refer on suspicion, keep the differential open, and let the result surprise you if it’s going to.
References
- World Health Organization Western Pacific. Dengue Situation Update #735: 27 November 2025. Manila: WHO Regional Office for the Western Pacific; 2025.
- Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. Am J Gastroenterol. 2016. PMID: 27995906.
- Fink J, Gu F, Vasudevan SG. Role of T cells, cytokines and antibody in dengue fever and dengue haemorrhagic fever. Rev Med Virol. 2006;16:263-275.
- Balasubramanian S, Janakiraman L, Kumar SS, Muralinath S, Shivbalan S. A reappraisal of the criteria to diagnose plasma leakage in dengue hemorrhagic fever. Indian Pediatr. 2006;43(4):334-339.
- Srikiatkhachorn A, Krautrachue A, Ratanaprakarn W, et al. Natural History of Plasma Leakage in Dengue Hemorrhagic Fever: A Serial Ultrasonographic Study. Pediatr Infect Dis J. 2007;26(4):283-290.