Dengue fever is an epidemic in Brazil and all over the world. Can a new vaccine stop it?

Dengue fever (pronounced den-gay) is a mosquito-borne disease that has been prevalent in a limited area for centuries, but is now spreading around the world at an unprecedented rate. This is an alarming example of how climate change and his 21st century demographics can rapidly change the situation. public health It will cause a terrible global health crisis.

In 2000, Approximately 500,000 dengue fever cases have been reported. and 19,685 dengue deaths recorded Worldwide; 5.2 million cases by 2019; 30,000 deaths, the highest number ever. Death tolls are on pace to set a new record in 2024.

It is highly likely that this disease will spread even higherThis is because dengue fever may be asymptomatic or have only mild symptoms, and the symptoms can be mistaken for other infections such as yellow fever or dengue fever. chikungunya virus.

In South and Southeast Asia, the Pacific Islands, and South America, which has been facing dengue fever for many years. Epidemics occur every 3 to 5 yearsthe virus has become a chronic threat.

in Brazil in January and February report With over 1 million cases Approximately 300 people died It is caused by dengue fever and is the fastest spreading virus ever recorded in this country. In Brazil, there will be 1.6 million dengue cases in all of 2023, already an 18% increase from the previous year.7 of her 26 states in Brazil declared a state of emergencyand the country has mobilized unprecedented vaccination campaignthe first ever nationalized dengue vaccine rollout.

Argentina is Over 74,000 cases experienced That's a staggering 2,100% increase since the beginning of this year compared to the same period in 2023.Peru declared a state of emergency More than 31,000 dengue cases were recorded in the first eight weeks of this year, and hospitals in the north were reported to be overwhelmed.

Bangladesh saw on the other side of the world More than 300,000 people infected with dengue fever Last year was the highest ever, triple the previous high in 2019. Between 2000 and 2022, Less than 1,000 people He died of dengue fever in the country. In 2023 alone, the disease killed 1,700 people.

And dengue fever is increasingly spreading in parts of the world where it has rarely been reported, including the United States.last year in california discovered First community transmission of dengue fever in history. Such incidents have occurred in recent years. report First time in France, Croatia, subtropical Africa, and Afghanistan.

Public health experts believe the main reasons for the increase in dengue fever are: two elements: climate change and rapid urbanization in developing countries. Both trends are expected to further strengthen in the coming years, meaning today's record dengue outbreaks may only be a sign of things to come.

Why is dengue fever suddenly spreading across the country?

Humanity has co-existed with dengue fever for thousands of years: the first recorded This case was published in Chinese medical encyclopedias from around 400 AD. In the 16th century, the mosquito species responsible for the spread of dengue fever (mainly Aedes aegypti and Aedes aegypti) moved around the world, partly due to the global slave trade. Outbreaks were reported regularly over the next several centuries and began to occur more frequently in the late 20th century.

many people Even if you are infected with dengue fever, there are no symptoms or only a mild fever, and you will recover in about a week. However, some patients develop more severe symptoms, including severe abdominal pain and vomiting. In a small number of cases, patients experience organ failure and even death.Estimated case fatality rate of dengue fever wide rangeIt ranged from 1 to 14 percent in various studies around the world, which likely partly reflects variations in the quality and timeliness of available treatment.

Since the 1950s, the number of severe cases and deaths from dengue fever has increased significantly. While increased awareness of dengue fever and improved diagnostics likely explain some of its rise, the dramatic spike in cases, especially in recent years, suggests that something larger is at work. It suggests that.

May be part of dengue fever surge due to expansion Increase in urban centers with tropical climates and increased travel to those areas.

The World Health Organization identified Climate change as another major cause of the rapid spread of dengue fever over the past 70 years.

Rising temperatures and associated changes in weather patterns make it easier for the mosquitoes that carry dengue fever to breed.For example, in Bangladesh, where dengue fever has been endemic for many years, the rainy season is It has been extended In recent years, it has been extended by more than a month. Wet weather and humidity can cause water to stagnate, making it easier for mosquitoes to breed.

Further north, Aedes mosquitoes are becoming more likely to settle in. One estimate The researchers calculated that from 1950 to 2018, climate change increased the global impact of dengue transmission from Aedes aegypti mosquitoes by 9 percent and from Aedes aegypti mosquitoes by 15 percent. In Europe, where dengue outbreaks have historically been rare, the study found that 2018 was the best year for dengue transmission ever recorded. historical climate record Dating back to 1900.Another climate model projected Compared to 2015 exposure levels, an additional 2.2 billion people are expected to be at risk of dengue exposure by 2080.

Mosquitoes that spread dengue fever breed in dense cities, especially in developing countries that lack advanced water and sanitation systems. Water buckets, discarded tires, flower pots, construction site debris, etc. all allow standing water to accumulate, creating a breeding ground for mosquitoes.

“Mosquitoes love shady aquariums,” says Rafael Melo Gallies, an infectious disease researcher at the Federal University of Rio de Janeiro. told science this month.

Travelers to areas where dengue is endemic can unknowingly bring the virus to new parts of the world, leading to local transmission, such as the case in California last year. This is likely to explain isolated cases.

What is the world doing to slow the dengue epidemic?

Public health authorities developed a playbook To combat dengue fever, which is similar to other mosquito-borne diseases such as malaria and yellow fever, people in dengue-prone areas should wear long-sleeved clothing, cover their beds with mosquito nets, and apply insect repellent. We encourage you to take precautions such as:

Countries currently battling acute infectious disease outbreaks are taking more aggressive measures.In Brazil, government officials Use Spray machines spray insecticides to kill disease-carrying mosquitoes in standing water in urban centres. (There are some evidence Local mosquitoes are becoming resistant to certain insecticides, potentially limiting the strategy's effectiveness).

But traditional strategies continue to lose the fight against climate change. We have more sophisticated measures at our disposal, but the challenge is to implement them in the field.

Brazil has already been forced to set up field hospitals as the number of infected people increases. deploy The latest dengue vaccine developed by Japan's Takeda Pharmaceutical Company in 2022. The vaccine was administered in clinical trials. 80 percent effective Significant improvement compared to previous vaccines in preventing symptomatic disease (previous vaccines had efficacy rates of 55 and 65 percentdepending on the specific strain of dengue).

However, there is not enough vaccine to quickly eradicate the outbreak in Brazil.The vaccine requires two doses, and this year Only 6 million doses Available in a country with a population of 214 million. Only 50 million doses are expected to be available in Brazil over the next five years.Vaccines are available at this time In only about 10% of Brazil's cities And eligibility is limited to pre-adolescent children (as well as the elderly), who are particularly susceptible to serious illnesses.

Competition for vaccines is likely to intensify in the coming years. At present, the Argentine government elected By making the dengue vaccine unavailable through the public health system, many people will no longer have access to it, as well as other preventive measures such as bug spray. Sold out. The situation could change if the epidemic worsens further.

Production may increase soon.Mr. Takeda Negotiating with India sell a certain amount of vaccines to the population health care The company plans to contract with local manufacturers to increase production capacity. The company said it aims to produce 100 million doses a year by 2030.

While this would represent progress, it will not be enough to cover everyone in areas vulnerable to dengue.

More vaccine candidates are in development, including a potentially game-changing one-dose version produced by Brazil's Butantan Institute. Under clinical trial, has proven to be highly effective against multiple dengue strains, which has long been a hurdle to vaccine development. However, final approval will still take at least a year, and even after that it will take time for full-scale production to ramp up.

Other cutting-edge technologies are also being deployed. At least five towns and cities in Brazil have introduced genetically modified mosquitoes to slow the spread of dengue fever. some promising results.

Since 2015, Niteroi, a city of 500,000 people, has been seeded with mosquitoes infected with a bacteria that makes the virus more difficult to transmit. The city reported fewer than 60 dengue cases last year, while neighboring Rio de Janeiro had nearly 10,000 cases. Another experiment using sterile male mosquitoes in a small town revealed that 97 percent reduction Number of dengue fever patients from 2020 to 2022.

For gene-edited mosquitoes, unique ethical difficulties. It could drive mosquito species to extinction and have unforeseen impacts on local ecosystems.

Other innovative products include: Residential paint containing pesticides, showed promising preliminary results. The researchers explore Can drugs used to treat hepatitis C be used to treat dengue fever patients?

The best strategy is probably an all of the above approach.That's the lesson of the world fight against malariaA combination of vaccines, insecticide-containing bed nets, and antimalarial drugs has proven highly effective in reducing the number of cases.

As the planet continues to warm, the spread of tropical diseases such as dengue fever is no longer just a problem in the Global South.already there some evidence Other mosquito-borne diseases, such as chikungunya virus, are following a similar path. The entire world needs to work together to find solutions to ensure that the current dengue crisis does not presage larger outbreaks in the future.