Latest news with #Wolbachia
Scoop
a day ago
- Health
- Scoop
Increased Movement Of People Making Dengue Outbreaks More Common, Says Mosquito Expert
Greg Devine said mosquitos that carry the virus 'hitchhike around the world' and the increased movement of people is increasing those infected by dengue. Caleb Fotheringham, RNZ Pacific Journalist Dengue fever outbreaks have been surging in recent decades but new initiatives like infecting mosquitos with bacteria or genetic modification could dramatically slow the spread. According to the World Health Organization there was just over 500,0000 reported cases in 2000 – ballooning to 5.2 million in 2019. Last year, there were 14 million dengue cases – a record number dwarfing the previous 2023 high of 6.5 million. This year, there's been 2.5 million. Samoa, Fiji, Tonga and the Cook Islands have all declared dengue outbreaks. Samoa, Fiji and Tonga have each had at least one death from the viral infection. Greg Devine from the World Mosquito Program said increased globalisation is making outbreaks more common. Devine said mosquitos that carry the virus 'hitchhike around the world' and the increased movement of people is increasing those infected by dengue. Devine said a lot of people also don't have immunity. 'They don't have any protection against it because they've never been exposed to it before,' he said. 'Dengue comes in four different serotypes, so just because you've had one doesn't mean you can't get another.' He said climate change was having an increasing impact. 'We are hotter and wetter than we've ever been before and that's great for mosquitoes. It also means that the virus in mosquitoes is replicating more rapidly.' The aedes aegypti mosquito – which carries dengue – is considered a tropical or subtropical mosquito, but Devine said warmer weather would also increase the mosquitoes' range of where it inhabits. In the Pacific, health ministries are trying to stamp out mosquito breeding grounds and are spraying insecticides outside. But Devine said doing so has had limited success in reducing the spread. He said the aedes aegypti mosquito is 'completely reliant upon humans for its blood meals' which meant it liked to stay indoors, not outdoors where the majority of the spraying happens. 'Outdoor use of insecticides, it's perhaps better than nothing and the truth is that the community wants to see something happening. 'That's a very visible intervention but the reality is, there's a very limited evidence base for its impact.' Mosquitoes continually exposed to insecticides would also evolve resistance, Devine said. The World Mosquito Programme infects mosquitos with a naturally occurring bacteria called Wolbachia, which stops viruses like dengue growing in the mosquitoes' bodies. 'It's been trialled in New Caledonia, where it's been extremely successful,' Devine said. 'In the years since, the mosquito releases have been made by the World Mosquito Program, there's been no dengue epidemics where once they were extremely common.' He said genetically modified mosquitoes were also being looked at as a solution. 'That's a different kind of strategy, where you release large numbers of mosquitoes which have been modified in a way which means when those males interact with the local mosquito female population, the resulting offspring are not viable, and so that can crash the entire population.' When asked if that could collapse the entire aedes aegypti mosquito population, Devine said he wouldn't be 'particularly worried about decimating numbers'. 'People often refer to it as the kind of cockroach of the mosquito world. 'It's very, very closely adapted to the human population in most parts of its range. The species evolved in Africa and has since, spread throughout the world. It's not a particularly important mosquito for many ecosystems.'
Scoop
a day ago
- Health
- Scoop
Increased Movement Of People Making Dengue Outbreaks More Common, Says Mosquito Expert
Greg Devine said mosquitos that carry the virus 'hitchhike around the world' and the increased movement of people is increasing those infected by dengue. Caleb Fotheringham, RNZ Pacific Journalist Dengue fever outbreaks have been surging in recent decades but new initiatives like infecting mosquitos with bacteria or genetic modification could dramatically slow the spread. According to the World Health Organization there was just over 500,0000 reported cases in 2000 – ballooning to 5.2 million in 2019. Last year, there were 14 million dengue cases – a record number dwarfing the previous 2023 high of 6.5 million. This year, there's been 2.5 million. Samoa, Fiji, Tonga and the Cook Islands have all declared dengue outbreaks. Samoa, Fiji and Tonga have each had at least one death from the viral infection. Greg Devine from the World Mosquito Program said increased globalisation is making outbreaks more common. Devine said mosquitos that carry the virus 'hitchhike around the world' and the increased movement of people is increasing those infected by dengue. Devine said a lot of people also don't have immunity. 'They don't have any protection against it because they've never been exposed to it before,' he said. 'Dengue comes in four different serotypes, so just because you've had one doesn't mean you can't get another.' He said climate change was having an increasing impact. 'We are hotter and wetter than we've ever been before and that's great for mosquitoes. It also means that the virus in mosquitoes is replicating more rapidly.' The aedes aegypti mosquito – which carries dengue – is considered a tropical or subtropical mosquito, but Devine said warmer weather would also increase the mosquitoes' range of where it inhabits. In the Pacific, health ministries are trying to stamp out mosquito breeding grounds and are spraying insecticides outside. But Devine said doing so has had limited success in reducing the spread. He said the aedes aegypti mosquito is 'completely reliant upon humans for its blood meals' which meant it liked to stay indoors, not outdoors where the majority of the spraying happens. 'Outdoor use of insecticides, it's perhaps better than nothing and the truth is that the community wants to see something happening. 'That's a very visible intervention but the reality is, there's a very limited evidence base for its impact.' Mosquitoes continually exposed to insecticides would also evolve resistance, Devine said. The World Mosquito Programme infects mosquitos with a naturally occurring bacteria called Wolbachia, which stops viruses like dengue growing in the mosquitoes' bodies. 'It's been trialled in New Caledonia, where it's been extremely successful,' Devine said. 'In the years since, the mosquito releases have been made by the World Mosquito Program, there's been no dengue epidemics where once they were extremely common.' He said genetically modified mosquitoes were also being looked at as a solution. 'That's a different kind of strategy, where you release large numbers of mosquitoes which have been modified in a way which means when those males interact with the local mosquito female population, the resulting offspring are not viable, and so that can crash the entire population.' When asked if that could collapse the entire aedes aegypti mosquito population, Devine said he wouldn't be 'particularly worried about decimating numbers'. 'People often refer to it as the kind of cockroach of the mosquito world. 'It's very, very closely adapted to the human population in most parts of its range. The species evolved in Africa and has since, spread throughout the world. It's not a particularly important mosquito for many ecosystems.'
Scoop
a day ago
- Health
- Scoop
Increased Movement Of People Making Dengue Outbreaks More Common, Says Mosquito Expert
Caleb Fotheringham, RNZ Pacific Journalist Dengue fever outbreaks have been surging in recent decades but new initiatives like infecting mosquitos with bacteria or genetic modification could dramatically slow the spread. According to the World Health Organization there was just over 500,0000 reported cases in 2000 - ballooning to 5.2 million in 2019. Last year, there were 14 million dengue cases - a record number dwarfing the previous 2023 high of 6.5 million. This year, there's been 2.5 million. Samoa, Fiji, Tonga and the Cook Islands have all declared dengue outbreaks. Samoa, Fiji and Tonga have each had at least one death from the viral infection. Greg Devine from the World Mosquito Program said increased globalisation is making outbreaks more common. Devine said mosquitos that carry the virus "hitchhike around the world" and the increased movement of people is increasing those infected by dengue. Devine said a lot of people also don't have immunity. "They don't have any protection against it because they've never been exposed to it before," he said. "Dengue comes in four different serotypes, so just because you've had one doesn't mean you can't get another." He said climate change was having an increasing impact. "We are hotter and wetter than we've ever been before and that's great for mosquitoes. It also means that the virus in mosquitoes is replicating more rapidly." The aedes aegypti mosquito - which carries dengue - is considered a tropical or subtropical mosquito, but Devine said warmer weather would also increase the mosquitoes' range of where it inhabits. In the Pacific, health ministries are trying to stamp out mosquito breeding grounds and are spraying insecticides outside. But Devine said doing so has had limited success in reducing the spread. He said the aedes aegypti mosquito is "completely reliant upon humans for its blood meals" which meant it liked to stay indoors, not outdoors where the majority of the spraying happens. "Outdoor use of insecticides, it's perhaps better than nothing and the truth is that the community wants to see something happening. "That's a very visible intervention but the reality is, there's a very limited evidence base for its impact." Mosquitoes continually exposed to insecticides would also evolve resistance, Devine said. The World Mosquito Programme infects mosquitos with a naturally occurring bacteria called Wolbachia, which stops viruses like dengue growing in the mosquitoes' bodies. "It's been trialled in New Caledonia, where it's been extremely successful," Devine said. "In the years since, the mosquito releases have been made by the World Mosquito Program, there's been no dengue epidemics where once they were extremely common." He said genetically modified mosquitoes were also being looked at as a solution. "That's a different kind of strategy, where you release large numbers of mosquitoes which have been modified in a way which means when those males interact with the local mosquito female population, the resulting offspring are not viable, and so that can crash the entire population." When asked if that could collapse the entire aedes aegypti mosquito population, Devine said he wouldn't be "particularly worried about decimating numbers". "People often refer to it as the kind of cockroach of the mosquito world. "It's very, very closely adapted to the human population in most parts of its range. The species evolved in Africa and has since, spread throughout the world. It's not a particularly important mosquito for many ecosystems."
Straits Times
2 days ago
- Health
- Straits Times
Singapore's dengue numbers are down. Should we still be concerned about it?
There were 2,219 dengue cases between January and June 5, compared with the 10,000 cases in the first six months of 2024. PHOTO: ST FILE Simply Science Singapore's dengue numbers are down. Should we still be concerned about it? SINGAPORE – The number of dengue cases in Singapore has dropped significantly in 2025 , constituting only about a quarter of the cases recorded in the first half of 2024. Data from the National Environment Agency's (NEA) website shows there were 2,219 cases between January and June 5, compared with the 10,000 cases in the first six months of 2024. The agency attributed the decline in number partly to innovations such as Project Wolbachia – an initiative to control the Aedes aegypti mosquito population through the release of lab-grown male mosquitoes. Does this mean that Singapore's control measures – which include fogging, home inspections and public education – are working, and that dengue is no longer a threat here? Experts told Simply Science that it may be premature to say if the existing measures can curb future dengue outbreaks. Under Project Wolbachia, male mosquitoes infected with Wolbachia – a common, naturally occurring bacteria – are released into high-risk dengue areas. When they mate with female mosquitoes, the eggs produced will not hatch, leading to a reduction in the mosquito population over time. The initiative currently covers 23 areas in Singapore, including Bukit Batok, Tampines and Serangoon. It aims to protect 800,000 households, or about half of all households here, by 2026. Studies have shown that residents in these areas are 75 per cent less likely to contract dengue, with the Aedes aegypti mosquito population in the areas falling by between 80 per cent and 90 per cent. Professor Ooi Eng Eong of Duke-NUS Medical School described the addition of Project Wolbachia to Singapore's vector control programme since 2016 as a 'positive development', noting that the lower number in 2025 compared with the same period in 2024 is 'good news'. 'However, tempting as it may be, it is premature to attribute the current trends to any specific intervention,' said the expert in emerging infectious diseases. Dengue epidemics do not occur annually but rather in five to eight-year cycles, said Prof Ooi, adding that fluctuations in mosquito population density are just one reason for the cyclical outbreaks. 'Other factors, such as population immunity to each of the four dengue viruses and genetic changes in dengue viruses circulating in Singapore, also affect dengue virus transmission and hence the number of dengue cases.' There are four dengue serotypes, or strains, with DenV-2 having been the dominant one in the Republic since September 2023. 'Thus, although tempting, short-term changes in dengue case trends after the introduction of new dengue control measures should be interpreted with caution,' Prof Ooi said. 'Moreover, as our last epidemic was in 2022, trends in dengue cases in 2025 are likely too soon to conclude that the current control measures can effectively prevent future outbreaks.' Professor Tikki Pang, a visiting professor at NUS' Yong Loo Lin School of Medicine, noted that similar initiatives in other countries, such as Malaysia, Indonesia and Australia, had shown positive results as well. He cited two other possible reasons for the drop in dengue cases – seasonal variation and effective mosquito control. Singapore typically sees fewer dengue cases outside the May to October peak period. NEA has also credited community vigilance – such as efforts to clear stagnant water to prevent mosquito breeding – as a key reason why a major outbreak was avoided. In 2022, Singapore reported 32,325 cases of dengue, the second-highest annual total on record. In May, NEA warned that despite the lower number of cases so far in 2025 , Singapore's low population immunity – as well as a global rise in cases – could potentially lead to an increase in dengue cases. The agency noted that the May to October period usually sees higher dengue transmission here due to the accelerated development of Aedes mosquitoes and the more rapid spread of the dengue virus in the mosquitoes. It reminded people to take actions such as overturning pails and changing water in vases to prevent the breeding of mosquitoes. According to figures from the World Health Organisation, more than 13 million dengue cases were reported globally in 2024 – more than double the 6.5 million recorded in 2023. Simply Science is a series that looks at the science behind everyday questions. Zhaki Abdullah is a correspondent at The Straits Times. He is on the health beat, in addition to occasionally covering science, environmental, tech and Muslim affairs issues. Join ST's WhatsApp Channel and get the latest news and must-reads.
Scoop
6 days ago
- Health
- Scoop
Dengue In The Pacific Region – Expert Q&A
Press Release – Science Media Centre The SMC asked experts about the current situation in the Pacific. The Cook Islands declared a dengue outbreak in Rarotonga last week. Other Pacific nations including Sāmoa, Tonga, and Fiji are also experiencing outbreaks. The SMC asked experts about the current situation in the Pacific. Dr Gregor Devine, Senior Director, Field Entomology at the World Mosquito Program, comments: What is the immediate threat posed by dengue in the wider Pacific region, and how is this changing? 'Dengue fever is the world's most prevalent disease spread by mosquitoes. Cases are increasing across the Western Pacific (e.g., Pacific Island Countries and Territories, Laos, Cambodia, Vietnam) and South East Asia (e.g., Bangladesh, Indonesia, Thailand, and Timor-Leste). All of these countries experienced significant dengue outbreaks in 2024 and 2025, and the general trend in cases globally is relentlessly upwards. 'These increases are fuelled by 1) climate change (increased temperatures encourage mosquito proliferation and shorten the time needed for viruses to replicate in their mosquito hosts), 2) increasing globalisation (and the increased movement of humans carrying the virus), 3) immunological naïveté, where human populations are being exposed to new dengue serotypes, and 4) the limited impact of existing control measures. 'According to the Pacific Syndromic Surveillance System, as of May 27th 2025, dengue cases are increasing or peaking in Fiji, Samoa, Tonga, Kiribati, and Cook Islands. There have been deaths reported from Fiji, Tonga and Samoa.' What hopes are currently on the horizon for new technologies or programmes to combat the disease? 'Current responses to dengue outbreaks largely involve the application of insecticides and the implementation of environmental 'clean-up' campaigns, but these have limited impacts. Moreover, resistance to insecticides is increasingly documented in the Pacific, and this further reduces the impact of conventional vector control. 'A safe, effective and sustainable solution exists. The Wolbachia method, developed by the non-profit World Mosquito Program, involves releasing mosquitoes infected with a bacteria that reduces their ability to transmit dengue. It has been proven to have a tremendous impact on dengue transmission around the world. Wolbachia releases have been piloted in Fiji, Vanuatu, Kiribati, and New Caledonia. Following six years of Wolbachia mosquito releases in New Caledonia, the project has been hailed a monumental success, and the French territory hasn't had a dengue epidemic since 2019. This year, releases will continue in Kiribati, and be adopted in Timor-Leste.' What is your biggest concern and/or is there anything you wish people understood better about the situation? 'The upward trend in dengue case numbers regionally will inevitably stress public health systems and impact family well-being (through both the health and economic costs of hospitalisation and the lost earnings of the sick). Sustainable ways to combat dengue, such as the Wolbachia method, are desperately needed. Vaccines are still years away from being universally affordable and applicable.' Conflict of interest statement: Greg Devine is the Senior Director of Field Entomology for the World Mosquito Program Dr Joan Ingram, Medical Advisor, Immunisation Advisory Centre, comments: What is the immediate threat posed by dengue in the Pacific region, and how is this changing? 'Dengue outbreaks are currently affecting Kiribati, Samoa, Fiji, Tonga and French Polynesia with the most cases being reported from Fiji, according to The Pacific Community (SPC). Case numbers are increasing in all of those areas, apart from in French Polynesia. There are four dengue serotypes – and both serotype 1 and serotype 2 are currently circulating. 'The Pacific Islands are vulnerable to dengue outbreaks as they have high levels of mosquitoes and dengue viruses can be introduced by infected people. 'Between 2012 and 2021, there were 69 outbreaks of dengue fever among the Pacific Islands. However, they are not unique in having dengue fever – dengue is common in many other regions including the Americas, Africa, the Middle East and Asia. 'Globally, dengue cases were at a very high level in 2024, particularly in South America. Cases increased almost 30-fold there between 2000 and 2024. Urbanisation, globalisation and climate change have contributed to this increase.' What is your biggest concern and is there anything you wish people understood better about the situation? 'Dengue is often a leading cause of fever in risk countries. Estimates are that around 6 in 1000 travellers spending a month in a risk area become unwell with dengue, with up to 30% of them being hospitalised. 'Dengue is spread by common biting mosquitoes (various Aedes species), which thrive where humans live. The main way to avoid dengue is mosquito bite avoidance. Aedes mosquitoes (unlike the malaria-transmitting Anopheles) are daytime feeders, with two peak times of biting activity in the day – 2 to 3 hours after dawn, and mid-to-late afternoon. However, they may feed all day indoors or on overcast days. 'People should regularly apply effective repellent as well as using light-coloured clothing to cover up. In addition, they should take steps to reduce mosquitoes indoors (such as screens on windows and doors), and in the environment by emptying any water-holding containers.' What hopes are currently on the horizon for new technologies or programmes to combat the disease? 'Qdenga, a dengue vaccine, is available in 30 countries overseas but not in New Zealand. It protects against dengue serotype 1 and 2 very well, especially in people who have had previous dengue. Protection against serotypes 3 and 4 is still being evaluated. 'An earlier dengue vaccine increased the risk of severe dengue in people who had not had dengue previously. It does not seem as though Qdenga does that, but it is still being monitored and most authorities prefer to administer it to people with past dengue infection although the guidelines differ. 'A new hope for the future is the use of Wolbachia-infected Aedes aegypti. Wolbachia infection blocks the transmission of the dengue virus from mosquitoes. Trials are ongoing with promising results.' No conflicts of interest. Dr Berlin Kafoa, Director, Public Health Division at The Pacific Community (SPC), comments: What is the immediate threat posed by dengue in the Pacific region, and how is this changing? ' 1. Increasing morbidity due to escalating dengue outbreaks reported across the Pacific region with circulation of multiple serotypes. 'Dengue is actively circulating in at least six Pacific Island Countries and Territories (PICTs), including Fiji (>8,000 cases, 4 deaths), Tonga (793 cases, 3 deaths), French Polynesia (>2,000 cases), Samoa (110 cases, 1 death), Cook Islands, and Kiribati. Multiple serotypes (DENV-1, DENV-2, DENV-3) are co-circulating, increasing the risk of severe dengue due to secondary infections in populations with partial immunity. ' 2. Changing epidemiology and vulnerable populations 'There is a growing incidence of severe dengue amongst children and youth with no prior dengue exposure. There are older adults coming from areas historically free of dengue. This suggests immunity gaps, but the lack of updated seroprevalence data limits precise risk profiling. ' 3. Climate and mobility as amplifiers 'Climate change and variability (e.g., rainfall, temperature) is expanding mosquito habitats and altering transmission regional and international travel and trade from endemic areas (e.g., Southeast Asia, South America) raises the risk of virus introduction.' What hopes are currently on the horizon for new technologies or programmes to combat the disease? ' 1. A need for collaboration across sectors, agencies, and countries. 'Through the Pacific Public Health Surveillance Network (PPHSN), we are working with WHO and allied members to support countries with preparedness, detection and response to dengue and other arboviral diseases. This includes: Rapid risk assessments and technical guidance Laboratory supplies and testing algorithms and Strengthening PCR testing capabilities in countries. Subtyping and WGS/Whole-Genome Sequencing via reference labs (e.g., VIDRL in Australia). Dissemination of risk communication messages through multiple channels and sharing of best practices in risk communication and community engagement ' 2. A need for predictive analytics and early warning 'We are exploring predictive algorithms that integrate climate data (e.g., rainfall, temperature), flight and mobility data, and historical outbreak and seroprevalence data. These tools aim to forecast outbreak risks and optimize vector control timing.' ' 3. Vector control capacity building to promote a One Health approach. 'The Pacific Vector Network (PVN) launched in 2023, a service arm of PPHSN, supports a coordinated response to control of vector-borne disease in the region; practical entomology training for PICTs; mosquito surveys, mapping, and surveillance; and provision of vector control equipment and insecticides.' ' 4. New tools being tested 'Other new tools being tested in the region include pilot testing of new technologies such as Sterile Insect Technique (SIT) in French Polynesia, and trials of Wolbachia introduction in Fiji, Vanuatu, New Caledonia, and Kiribati. For possible consideration, there is the introduction of dengue vaccines-contingent on availability of sero-prevalence data.' What is your biggest concern and/or is there anything you wish people understood better? 'The real risk of severe dengue is rising. Severe cases and fatalities are being reported, especially among youth. Dengue should not be dismissed as a mild illness, it can be life-threatening. 'There are gaps in immunity and surveillance. Many populations remain immunologically naive due to limited past exposure. Inadequate seroprevalence data and diagnostic capacity hinder targeted responses. 'There are changes in vector behaviours with possible increase in behaviours resistance to insecticides. 'Dengue is not the only arboviral threat which further complicates surveillance, diagnosis, and response efforts. Other threats include: Zika: Imported cases have been reported in the Pacific Rim (e.g., New Zealand from Fiji). Chikungunya: A major outbreak in La Réunion (339,000+ cases) and an imported case in Wallis and Futuna. Yellow fever: While not yet reported in the Pacific, the presence of Aedes vectors makes introduction a real risk 'There is a need to support the Pacific to acquire new technology for genomic surveillance. Genetic sequencing of dengue strains is essential to track virus movement and mutations across the region, but capacity remains limited. 'Dengue is no longer a seasonal or isolated threat in the Pacific; it is a regional health emergency shaped by climate, mobility, and historical vulnerabilities. Through a One Health multisector, multiagency and multi-country collaborative efforts with WHO, PIHOA and PPHSN partners, we are responding and building the tools and intelligence to predict, prepare and hopefully prevent the next wave.'
