As Samoa battles dengue fever, here’s what you need to know about the mosquito-borne virus

Each morning in Samoa, fumigation teams gear up to spray schools and buildings, battling tirelessly against a dengue outbreak.

Since the outbreak was declared on April 17, Samoa’s Ministry of Health says more than 5,600 clinically diagnosed cases have been recorded. 

Tragically, to date, there have been four confirmed and one probable dengue-related death, highlighting the urgent fight still ahead.

This effort comes as the Pacific faces a severe surge in cases, with deaths now reported in Fiji, Tonga, and Nauru. Affected countries also include American Samoa, Cook Islands, Tahiti, Kiribati and Tuvalu.

So what is dengue fever? And why is this outbreak hitting the Pacific so hard?

 Samoa has rolled out a large-scale fumigation program in schools. (Image: Ministry of Health Samoa)What is causing the current dengue outbreak? 

Dengue fever is a viral disease spread by mosquitoes.

It is transmitted by the infected female Aedes mosquito and causes fever and joint pain. Some patients can suffer internal bleeding, which can cause death.

It has long plagued tropical nations, but health experts warn the 2025 outbreak is one of the worst in almost a decade.

This is largely because of: 

The movement of people between Pacific nationsChanging weather patterns — longer, wetter seasons linked to climate changeIncreased urban settingsPoor waste disposal practices, stagnant water, and overgrown vegetation In Fiji, the WHO’s July data shows the spread of the disease has been highest.(Source: Fiji’s Ministry of Health & Medical Services)

The World Health Organization’s Dr Mark Jacobs said the long-term pattern was one of peaks and troughs.

“Across the region, we’ll have some years where we get a big peak in cases and other years it’s very much lower level and a lot of Pacific countries don’t see any cases at all,” he told Pacific Beat.

“For a lot of Pacific countries, the biggest factor is when somebody who is infected with dengue and then a local mosquito bites them and spreads it. Because the dengue virus is only found in two types of animals: mosquitoes and people.

“You have people with dengue who then infect the mosquito, and then those mosquitoes infect more people. That’s how outbreaks happen.”

What are the symptoms?

Symptoms to watch for include fever, extreme fatigue, headache, nausea, vomiting, intense muscle and joint pains, and a distinct measles-like rash.

Dengue cases in the Pacific are at their highest since 2016, with nearly 19,000 people affected as of last month’s figures, the World Health Organisation (WHO) says.

Aedes aegypti is the primary spreader of dengue. Dengue is the most common mosquito-borne disease worldwide.(Supplied: Stephen Doggett, NSW Health Pathology)

There are four dengue viruses. 

“If you’ve been infected with dengue type one, and once you’ve recovered from that, you’re then protected from getting that type of dengue again. But if one of these other types comes into the countr,y you can be infected with that type of dengue,” Dr Jacobs said.

“It’s people getting dengue more than once that are most at risk of getting severe dengue.”

Globally, the WHO recorded more than 13 million dengue cases and 9,990 deaths in 2024.

Aedes aegypti mosquitoes are the primary spreaders of dengue, although another species — Aedes albopictus (commonly known as the Asian tiger mosquito) — can also carry the virus.

How can it be stopped?

Prevention measures include:

Eliminating stagnant/ standing water sources — like tyres, open buckets, water-holding containers, etcUse mosquito nets and repellentWearing long-sleeved clothingKeep the surrounding areas cleanCommunity spray

 In recent weeks, Samoa has been particularly affected.

Just in the past seven days, more than 1,400 new clinically diagnosed cases have been reported across Upolu and Savai’i.

There, families and villages have been urged to actively eliminate mosquito breeding sites by improving waste disposal, removing stagnant water, and clearing overgrown vegetation to reduce mosquito populations.

“The mosquitoes that spread dengue live locally,” Dr Jacobs said. 

“They’ll only travel 100-200 metres in their lives, so the precautions you take around your house could make a big difference.”

Adapting scientific solutions to the Pacific

A mosquito release program in Far North Queensland using Wolbachia bacteria helped reduce dengue transmission by making mosquitoes more resistant to the virus and less likely to infect humans.

Mosquitoes bred in jars as part of the World Mosquito Program’s dengue fever eradication program.(Supplied: World Mosquito Program) Dr Tessa Knox, co-lead of the Pacific Mosquito Strengthening for Impact (PacMOSSI) consortium.(Supplied.)

Although the method proved highly effective in Australia, applying similar scientific interventions in the Pacific presents unique challenges, Tessa Knox from PacMOSSI explains. 

“Not all mosquito control interventions are suitable for every setting. The Pacific Islands face numerous challenges: a diversity of mosquito species, remote and dispersed populations, limited human resources, fragile health systems, and competing health priorities.

“These factors create significant logistical, technical, and resource barriers. Locally tailored solutions are therefore essential.

“Across the Pacific, there is great diversity in the species that can transmit dengue. It is important to know which species are found in which habitats and understand when and where they bite people and transmit dengue.”

Fighting dengue with better mosquito control and insecticide use

PacMOSSI is working to support Pacific Island Ministries of Health to improve this knowledge to tailor control strategies against local dengue mosquitoes. The consortium connects 21 Pacific Island countries with seven international institutions to combat mosquito-borne diseases.

“Community-led approaches like removing rubbish in yards and public areas to reduce mosquito water habitats are essential. Knowing which species can be killed with which insecticides helps to select the best option for spray teams to use when responding to a dengue outbreak,” Dr Knox told ABC Pacific. 

A large-scale fumigation program in schools has been carried out with hope to stop the spread of dengue fever in Samoa. (Image: Ministry of Health Samoa)

Drawing on North Queensland’s success, she highlighted approaches with potential for long-term dengue control in the Pacific.

“Residual spraying with long-lasting insecticides has been effective for dengue control in North Queensland. Expertise from Queensland Health has supported outbreak response in Tonga, Samoa, Nauru, Tuvalu and Fiji through PacMOSSI, which has also provided equipment, training, and operational research support. 

“Similarly, the Wolbachia method trialled in Queensland has informed its broader global use. Experience in Australia is highly relevant for the Pacific, and PacMOSSI ensures this expertise benefits countries of the region.” 

Villages have been clearing rubbish as part of the clean-up to eliminate mosquito breeding grounds.(Image: Ministry of Women, Community and Social Development )

Posted 2h ago2 hours agoMon 4 Aug 2025 at 11:27pm, updated 1h ago1 hours agoTue 5 Aug 2025 at 12:01am