In Bangladesh, roughly 300,000 people have been infected with dengue this year during the country’s worst-ever outbreak of the mosquito-transmitted disease. By mid-November, the death toll hit close to 1,500, as hospitals in the densely populated South Asian country struggled to cope with the surge in patients.
Neighbouring India is also experiencing more and more outbreaks, along with Sri Lanka to the south, where 60,000 cases of dengue have been reported just this year. In Mexico, cases rose more than 330 per cent in 2023 compared to 2022, and Argentina, Bolivia, Brazil, and Peru are also reporting high rates of infections.
The disease — known as “breakbone fever,” due to the severe muscle and joint pains it can cause — is also appearing far beyond its usual range in tropical and subtropical climates.
The explosive spread of dengue, through the mosquitos known for carrying the virus, offers a case study in how climate change, human movement, and rising temperatures are all coaligning to fuel the expansion of potentially deadly threats to human health. And, scientists warn, even countries like Canada that have avoided dengue’s wrath could experience local transmission of the virus in the decades ahead.
“The frequency of outbreaks is ever increasing,” Himmat Singh, a scientist at the National Institute of Malaria Research in New Delhi, told the British Medical Journal. “Mosquitoes are evolving as humans have pushed them to adapt.”
WHO scientists ring alarms
While eye-catching climate impacts such as extreme weather events and heat waves will be front and centre at the first dedicated Health Day being held on Sunday at COP28, the World Health Organization (WHO) recently warned our changing climate is also “catalyzing a surge in infectious diseases like dengue” and is calling for health-focused climate action from global governments.
The organization’s chief scientist, Dr. Jeremy Farrar, told Reuters in October that he expects dengue will become a major threat in the southern U.S, southern Europe, and new parts of Africa this decade — as warmer temperatures create the conditions for the mosquitoes carrying the infection to spread.
Dengue virus is transmitted by the Aedes aegypti mosquito, a tropical species which also spreads the viruses behind diseases such as Zika, chikungunya, and yellow fever.
“They harbour a lot of these nasty viruses,” said virologist Stephen Barr, an associate professor in Western University’s department of microbiology and immunology. “What researchers know is that the traits these mosquitoes have, that are favourable for spreading these viruses, occur in the range of temperatures from about 24 to 29 C.”
A health worker fumigates mosquitos to help mitigate the spread of dengue inside a home, at La Primavera shantytown in Piura, Peru, Saturday, June 3, 2023. Dengue, a viral disease transmitted by a mosquito, causes flu-like symptoms, such as muscle pain and fever. (Martin Mejia/The Associated Press)
The species can survive year-round when temperatures are warm enough, and females lay their eggs in areas of shallow, stagnant water, which can mean spaces as small as household containers, potted plants, or even a bottle cap.
“Once the mosquito habitat is established, it only takes one or two people to bring the virus into that habitat for the mosquito to [spread it],” said Dr. Amila Heendeniya, a clinical infectious diseases physician at the Winnipeg Regional Health Authority and an assistant professor at the University of Manitoba.
In Pakistan, there has been an ongoing dengue epidemic since 2011, said Dr. Imran Hassan Khan, chair of the country’s Dengue Expert Advisory Group. The mosquitoes appear to be adapting to a longer rainy season, and now likely live throughout homes where they can infect people with this virus at any time of day, he explained.
“We’re unable to eradicate it,” he added. “It’s impossible to eradicate it.”
Rates of the disease have risen eight-fold around the world in the last two decades, WHO figures suggest. Scientists also suspect far more cases are going unreported, given the wide range of potential symptoms, from internal bleeding, organ failure and death on the severe end, all the way to mild ailments or even no symptoms at all.
Insect-borne infections on the rise thanks to climate change
Featured VideoDiseases carried by insects that infect humans, like Lyme disease and West Nile virus, are on the rise in Canada. The shorter, less severe winters due to climate change have allowed those insects to expand their range.
2nd infections can be worse than the 1st
One of the most alarming aspects of dengue’s rapid rise is that one exposure to the virus doesn’t protect you from infection with a different serotype — and can actually mean your second round is worse.
There are four distinct serotypes of dengue, explained Thais dos Santos, advisor for surveillance and control of arboviral diseases at the Pan American Health Organization (PAHO).
“In terms of immunity, they act as four distinct viruses,” she said, adding that one dengue infection is thought to provide life-long immunity to that specific serotype, but not the others. “Once you get that secondary infection it has been well-documented that you’re more likely to have severe symptoms.”
The mechanism at play is known as “antibody-dependent enhancement,” in which the antibodies against dengue produced by someone’s immune system fall to a low range. Research suggests that leads to a domino effect where the few antibodies still left are able to bind to the virus, pull it into cells, and give it space to replicate — but their level remains too low to actually kill those invaders.
“Your body starts fighting it, but not really properly,” explained Heendeniya, who said that haywire immune response leads to an increased risk of internal bleeding and hemorrhagic fever.
Why that reaction happens with dengue to a degree not seen in many other infections is still not fully understood, but researchers note what’s clear is that it complicates the use of vaccines. Two commercially available dengue vaccines are being used by various countries, but most global guidance recommends only vaccinating children in high-risk areas who have had a prior confirmed infection, given there’s also a risk for severe disease if someone catches dengue after immunization.
“I think we’re still trying to understand a lot of those mechanisms, and everyone’s immune system is going to be different… there’s so much we still don’t know,” said Barr.
The Wolbachia bacteria prevents the bugs from being able to transmit viruses such as dengue (World Mosquito Program)
Half of world’s population now at risk
Questions about how dengue operates are now more pressing as climate change and widespread human migration are expected to fuel its continued spread, with potentially dire consequences. Already, roughly half of the world’s population is now at risk, with an estimated 100 to 400 million infections occurring every year, the WHO has said.
“For the longest time, dengue was considered an ’emerging’ infectious disease,” Heendeniya said. “I would say it has already emerged.”
Modelling studies also project wider expansion of the virus within specific countries. One paper in the Lancet Planetary Health, for instance, projected a higher risk of dengue through much of mainland China by the year 2100.
As for Canada, the dengue virus isn’t found in mosquitos here — at least not yet. But Barr warns that could change. Local transmission in countries such as France and Croatia was only reported for the first time in 2010, WHO data shows.
Canada’s historically colder climate hasn’t provided the conditions for these mosquitoes to thrive year-round, Barr said. However, an adult Aedes aegyptiwas found in a trap in Ontario for the first time in 2017, a discovery health officials believe signaled the species is now becoming established.
Rising temperatures, Barr warned, could make this country more hospitable, and if more of these mosquitoes hitch a ride here, locally-acquired dengue infections in the years ahead could become a real possibility.
The Canadian government says it will donate up to 200,000 vaccine doses to fight the mpox outbreak in Congo and other African countries.
It says the donated doses of Imvamune will come from Canada’s existing supply and will not affect the country’s preparedness for mpox cases in this country.
Minister of Health Mark Holland says the donation “will help to protect those in the most affected regions of Africa and will help prevent further spread of the virus.”
Dr. Madhukar Pai, Canada research chair in epidemiology and global health, says although the donation is welcome, it is a very small portion of the estimated 10 million vaccine doses needed to control the outbreak.
Vaccine donations from wealthier countries have only recently started arriving in Africa, almost a month after the World Health Organization declared the mpox outbreak a public health emergency of international concern.
A few days after the declaration in August, Global Affairs Canada announced a contribution of $1 million for mpox surveillance, diagnostic tools, research and community awareness in Africa.
On Thursday, the Africa Centres for Disease Control and Prevention said mpox is still on the rise and that testing rates are “insufficient” across the continent.
Jason Kindrachuk, Canada research chair in emerging viruses at the University of Manitoba, said donating vaccines, in addition to supporting surveillance and diagnostic tests, is “massively important.”
But Kindrachuk, who has worked on the ground in Congo during the epidemic, also said that the international response to the mpox outbreak is “better late than never (but) better never late.”
“It would have been fantastic for us globally to not be in this position by having provided doses a much, much longer time prior than when we are,” he said, noting that the outbreak of clade I mpox in Congo started in early 2023.
Clade II mpox, endemic in regions of West Africa, came to the world’s attention even earlier — in 2022 — as that strain of virus spread to other countries, including Canada.
Two doses are recommended for mpox vaccination, so the donation may only benefit 100,000 people, Pai said.
Pai questioned whether Canada is contributing enough, as the federal government hasn’t said what percentage of its mpox vaccine stockpile it is donating.
“Small donations are simply not going to help end this crisis. We need to show greater solidarity and support,” he said in an email.
“That is the biggest lesson from the COVID-19 pandemic — our collective safety is tied with that of other nations.”
This report by The Canadian Press was first published Sept. 13, 2024.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.
Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.
Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.
Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.
The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.
“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.
Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.
Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.
Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.
A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.
This report by The Canadian Press was first published Sept. 10, 2024.
