Dengue fever could become endemic in Britain if a planned experiment for later this year backfires, experts warn.
Currently, the infection is only found in tropical parts of the world, such as areas of Africa, South America and the Caribbean, which is thought to have spread to southern Europe.
But researchers now deliberately want to give dengue to British people, who can then continue their normal lives, MailOnline has learned.
Health chiefs have yet to approve the trial, which the company behind the proposal wants to hold at an unconfirmed date in London.
Mosquitoes usually spread the infection, nicknamed “breakbone fever” because of the agonizing pain it inflicts on sufferers.
This map shows areas where dengue-transmitting mosquitoes have been introduced to Britain. These populations have not yet established themselves permanently in the UK, but experts have warned that climate change means their spread is inevitable
In rare cases, dengue can be contracted from exposure to infected blood.
Therefore, volunteers will be told to avoid a number of activities that could cause another person to become infected.
These include not donating blood, visiting a dentist, or playing high contact sports for at least 21 days after infection.
Despite the precautions taken, experts say the “unusual” experiment carries an “inevitable” risk of inadvertently infecting other Britons.
Independent experts also argued that there is a risk that the trial could seed dengue in mosquitoes in the UK, effectively making the disease endemic.
Once infected, mosquitoes can transmit the disease for the rest of their lives.
One of the two mosquito species responsible for most cases of dengue worldwide – the tiger mosquito – is already found in Britain.
No domestic infections have been recorded to date, yet dozens are imported each year.
Experts have warned that climate change will eventually put an end to that, with rising temperatures increasing mosquitoes’ range.
It is currently thought that most tiger mosquitoes do not survive winter in the UK, but the species can effectively establish itself permanently through eggs that can survive the cooler temperatures.
Dr. Richard Ebright, a molecular biologist at Rutgers University in New Jersey, said the proposed study increases the risk of dengue becoming endemic in the UK.
“It’s a numbers game,” he said, explaining that increasing the number of dengue-positive people later increased their risk of being bitten by a mosquito that could be infected.
Dr. Ebright added that travel bans should be put in place for the study participants, among other precautions.
Professor Robert Dingwall, who advised the government during Covid, also said the proposed research had inherent risks.
“The mosquitoes that carry it between humans could become established in the UK as a result of climate change,” he said.
“Some important immunological questions can only be answered by this type of research, although there are inherent risks for the volunteers, for the professionals conducting the research and for the wider community.”
However, he said the biggest risk was the volunteers’ willingness to follow the rules.
“For me, the biggest problem would be directing the volunteers and making sure they follow the safety rules,” he said.
‘While the UK has fairly tight controls over who can take part in trials and how much they can be paid, it’s not easy to control their behavior once they leave a clinic.
“Security controls that look good on paper are notoriously difficult to make work in practice.”
Dengue infects an estimated 400 million people each year and kills about 40,000.
Health chiefs have yet to approve the trial, which will take place in London. It is run by a private company.
The proposed trial, described as ‘not common’ by the workplace safety watchdog the Health Safety Executive (HSE), is a ‘Controlled Human Infection Model’ – a type of study that examines how diseases infect people.
Such models are considered an essential part of future vaccine development.
Government-appointed experts consulted on the proposal have recommended that the study be held over the winter.
They stated that this will help reduce the risk of mosquitoes being active that can transmit dengue between humans.
Dengue is normally transmitted through mosquito bites, but exposure to infected blood can also cause people to contract the virus
They also called on participants to get a dengue vaccine when the trial is over.
The company must also specify how many volunteers it plans to recruit for the study, as this would affect the risk to the general public, advisers ruled.
HSE told MailOnline that the name of the company seeking approval for the study could not be disclosed for “commercial reasons”.
The application is still “pending,” the agency confirmed.
Professor Paul Hunter, an infectious disease expert from the University of East Anglia, said this kind of research always carried a risk of later infections.
“Any use of a live, fully virulent virus in clinical trials carries the risk of secondary infections,” he said.
However, he added that given that dengue was already being regularly imported into the UK, the trial did not pose any additional risk compared to existing cases.
“We’ve seen imported dengue cases in the UK quite regularly anyway with no secondary cases as far as I know,” he said.
A 2016 study found that dengue was responsible for around one in five tropical infections requiring hospital treatment among travelers arriving or returning from Asia in the UK.
However, Professor Hunter added that another concern is that because dengue causes more serious illness with later infections, volunteers could be at risk if they contract the virus naturally in the future.
Among other precautions, volunteers willing to be infected with dengue are asked to carry a card for medics in case they need emergency treatment.
This will alert staff to their dengue infection status so that medics can take appropriate safety precautions, such as using personal protective equipment, to avoid exposure to their blood.
Volunteers will have blood samples taken daily for the first two days after infection, then every other day for the next 19 days of the study.
The strain of dengue used in the study is believed to have a milder form of the disease that produces less severe symptoms found in 1974.
Dengue usually causes a series of flu-like symptoms such as fever, headache, pain, nausea, swelling and rash for one to two weeks, but it can develop into a serious and fatal infection.
Dengue is one of the diseases experts have warned will eventually take hold in Britain thanks to climate change making the UK more hospitable to their carriers.
Transmission of the virus, as opposed to imported cases, has become a growing health concern in Europe as it marches north from the tropics.
Health authorities have warned that mosquitoes that can transmit dengue have now become firmly established around the Mediterranean, with subsequent outbreaks of the virus in these areas.