Skip to main content

Mosquitoes, Dengue Fever, and the Quest for a Dengue Vaccine

 

Dengue fever is a viral infection that affects millions of people around the world every year. It is transmitted by the bite of infected mosquitoes, mainly the Aedes aegypti species, which are found in tropical and subtropical regions. Dengue fever can cause a range of symptoms, from mild to severe, and sometimes even fatal. There is no specific treatment or cure for dengue fever, and the only way to prevent it is to avoid mosquito bites and control the mosquito population. In this blog post, we will explore what dengue fever is, how it affects people, and what efforts are being made to develop a vaccine against it.

What is dengue fever?

Dengue fever is caused by one of four types of dengue virus (DENV), which belong to the flavivirus family. The virus enters the human body through the saliva of an infected mosquito, and then multiplies in various tissues and organs, especially the lymph nodes, spleen, liver, and blood vessels. The virus can also infect some immune cells, such as macrophages and dendritic cells, and interfere with their function.

The incubation period of dengue fever is usually 4–10 days, after which the symptoms may appear. According to the World Health Organization (WHO), about 25% of people infected with dengue virus develop symptoms, while the rest remain asymptomatic or have mild illness.

The symptoms of dengue fever include:

·        High fever (40°C/104°F)

·        Severe headache

·        Pain behind the eyes

·        Muscle and joint pains

·        Nausea

·        Vomiting

·        Swollen glands

·        Rash

These symptoms usually last for 2–7 days, and then subside. However, some people may experience a second phase of illness, known as severe dengue or dengue hemorrhagic fever (DHF). This occurs when the virus triggers a severe immune response that damages the blood vessels and causes bleeding, shock, organ failure, and death. The risk of severe dengue is higher for people who have been infected with a different type of dengue virus before, as this can cause a phenomenon called antibody-dependent enhancement (ADE), where the antibodies from the previous infection enhance the entry and replication of the new virus instead of neutralizing it.

The symptoms of severe dengue may include:

  • ·     Severe abdominal pain
  • ·        Persistent vomiting
  • ·        Rapid breathing
  • ·        Bleeding from the gums or nose
  • ·        Blood in the urine, stool or vomit
  • ·        Bleeding under the skin, which might look like bruising
  • ·        Difficult or rapid breathing
  • ·        Fatigue
  • ·        Irritability or restlessness

Severe dengue is a medical emergency that requires immediate hospitalization and supportive care. The fatality rate of severe dengue can be as high as 20%, but can be reduced to less than 1% with proper management.

How common is dengue fever?

Dengue fever is one of the most widespread mosquito-borne diseases in the world. According to WHO estimates, about half of the world's population is now at risk of dengue infection, with an estimated 100–400 million cases occurring each year. Dengue fever is endemic in more than 100 countries in Africa, Asia, Latin America, and the Caribbean. The disease is also expanding its geographic range due to factors such as urbanization, globalization, climate change, and lack of effective vector control.

The global burden of dengue fever has increased dramatically in recent decades. The number of cases reported to WHO increased from 505,430 in 2000 to 5.2 million in 2019. The number of deaths due to dengue fever also rose from 960 in 2000 to 4,032 in 2019. Dengue fever causes significant morbidity and mortality, especially among children and young adults. It also imposes a huge economic and social cost on affected countries and communities.

How can dengue fever be prevented?

There is currently no approved vaccine or medication that protects against dengue fever. The only way to prevent dengue fever is to avoid being bitten by mosquitoes and to take steps to reduce the mosquito population. Some of the strategies that can help prevent mosquito bites include:

  • ·        Using insect repellents containing DEET, picaridin or oil of lemon eucalyptus on exposed skin and clothing.
  • ·        Wearing long-sleeved shirts and long pants when outdoors.
  • ·        Staying indoors during peak mosquito activity hours (dawn and dusk).
  • ·        Installing screens on windows and doors to keep mosquitoes out.
  • ·        Sleeping under a mosquito net or in an air-conditioned room.
  • ·        Eliminating or covering any potential breeding sites for mosquitoes, such as containers that hold water, tires, flower pots, etc.

Some of the strategies that can help reduce the mosquito population include:

  • ·        Spraying insecticides or larvicides in areas where mosquitoes breed or rest.
  • ·        Introducing biological control agents, such as fish, bacteria, or fungi, that kill mosquito larvae or adults.
  • ·        Releasing genetically modified or sterile male mosquitoes that mate with wild females and reduce their offspring.
  • ·        Releasing Wolbachia-infected mosquitoes that reduce the ability of dengue virus to replicate and spread in the mosquito population.

These strategies require coordinated efforts from governments, communities, and individuals to be effective and sustainable.

What is the status of dengue vaccine development?

Several efforts are underway to develop a safe and effective vaccine against dengue fever. However, developing a dengue vaccine is challenging for several reasons, such as:

  • ·    The need to protect against all four types of dengue virus, which have different antigenic properties and can cause cross-reactive immune responses that may enhance disease severity.
  • ·        The lack of a reliable animal model that mimics human dengue infection and disease.
  • ·        The ethical and logistical difficulties of conducting large-scale clinical trials in endemic areas.

Despite these challenges, some progress has been made in dengue vaccine research. The first dengue vaccine to be licensed was Dengvaxia, developed by Sanofi Pasteur. Dengvaxia is a live attenuated tetravalent vaccine that contains four recombinant viruses derived from the yellow fever vaccine strain. Dengvaxia was approved in 2015 in Mexico and has since been authorized in several countries in Asia and Latin America. However, Dengvaxia has shown limited efficacy and safety issues in some populations. In 2017, it was found that Dengvaxia could increase the risk of severe dengue in people who had not been previously exposed to dengue virus. As a result, WHO recommended that Dengvaxia should only be used in people who have had a confirmed prior dengue infection.

Other dengue vaccines are currently in various stages of development and testing. Some of the promising candidates include:

·        TAK-003: A live attenuated tetravalent vaccine developed by Takeda. TAK-003 has shown high efficacy and safety in phase 3 trials involving more than 20,000 children and adolescents in Asia and Latin America. TAK-003 is expected to be submitted for regulatory approval soon.

·        TV003/TV005: A live attenuated tetravalent vaccine developed by the National Institutes of Health (NIH) and Butantan Institute. TV003/TV005 has shown high efficacy and safety in phase 2 trials involving more than 4,000 adults in Brazil. TV003/TV005 is currently undergoing phase 3 trials in Brazil, Thailand, Vietnam, Colombia, and Nicaragua.

·        DENVax: A live attenuated tetravalent vaccine developed by Merck. DENVax has shown promising results in phase 1 trials involving more than 100 adults in the U.S. and Singapore. DENVax is currently undergoing phase 2 trials in Singapore, Thailand, Colombia, and Puerto Rico.

In addition to these live attenuated vaccines, other types of vaccines are also being explored, such as subunit vaccines, DNA vaccines, mRNA vaccines, viral vector vaccines, and nanoparticle vaccines. These vaccines may offer advantages such as improved stability, safety, immunogenicity, and scalability.

Conclusion

Dengue fever is a serious global health problem that affects millions of people every year. There is no specific treatment or cure for dengue fever, and the only way to prevent it is to avoid mosquito bites and control the mosquito population. Several efforts are underway to develop a safe and effective vaccine against dengue fever, but none have been approved yet. Until then, we need to continue to raise awareness and implement preventive measures to reduce the burden of this disease.

 

 

 

 


Labels:

Comments

Post a Comment

Popular Posts

Heart Related Causes of Chest Pain: A Comprehensive Guide

  Chest pain is a common symptom that can have many different causes. Some of them are related to the heart, while others are not. In this blog post, we will explore the most common heart-related causes of chest pain, how to recognize them, and what to do if you experience them. Heart-related causes of chest pain include: Angina: This is a type of chest pain that occurs when the heart muscle does not get enough blood and oxygen. It usually happens during physical exertion, emotional stress, or exposure to cold. Angina can feel like pressure, squeezing, tightness, or heaviness in the chest. It may also radiate to the neck, jaw, shoulders, arms, or back. Angina is a sign of coronary artery disease (CAD), which is the narrowing or blockage of the arteries that supply blood to the heart. Angina can be stable or unstable. Stable angina is predictable and occurs with a certain level of activity or stress. Unstable angina is unpredictable and can occur at rest or with minimal exertion. Unstab
Post a Comment
Read more

Coronavirus Variants Unveiled: Understanding the Threat, Symptoms, Treatment, Prevention, and Updates of JN.1

  The coronavirus pandemic has been raging for more than two years , and it shows only little signs of slowing down. As the virus spreads and mutates, new variants emerge that pose different challenges for public health and vaccine development. One of the latest variants to be detected is JN.1, which was first reported in Japan in October 2021. What is JN.1 and why is it concerning? JN.1 is a descendant of the Omicron strain of SARS-CoV-2, which is currently the dominant strain of the coronavirus worldwide. JN.1 has several mutations in its spike protein, which is the part of the virus that attaches to human cells and allows infection. Some of these mutations are similar to those found in other variants of concern, such as Alpha, Beta, and Omicron. According to the World Health Organization (WHO), JN.1 has been detected in at least 19 countries as of December 2021, including Japan, South Korea, China, India, Australia, Canada, Singapore and the United States. However, its global preval
Post a Comment
Read more

Anthrax: Understanding the Deadly Bacterium

  Anthrax is a serious infectious disease that can affect both humans and animals. It is caused by a type of bacteria called Bacillus anthracis, which can form spores that can survive in harsh conditions for a long time. Anthrax spores can be found in soil, plants, or water, and can infect animals that graze or drink from contaminated sources. People can get anthrax if they come in contact with infected animals or their products, such as wool, hide, or meat. Anthrax is not contagious, which means it cannot spread from person to person like the flu or the cold. Types of Anthrax Infection There are four types of anthrax infection in humans, depending on how the spores enter the body: cutaneous, inhalation, gastrointestinal, and injection . Each type has different symptoms and requires different treatment. Anthrax can be fatal if not treated promptly with antibiotics. In some cases, anthrax can also cause a severe allergic reaction called anthrax toxin-mediated shock, which can lead to or
Post a Comment
Read more

Benefits of Vitamins to Eye Health

  Vitamins can help your eyes in many ways. They can protect them from infections, inflammation, and vision loss. In this post, we will share some of the best vitamins for eye health and how to get them from your food. Your eyes are amazing. They let you see the colors, shapes, and movements of the world. But they also need care and nourishment. That's why you should eat foods that are rich in vitamins that support your eye health. What are vitamins and why are they important for eye health? Vitamins are organic compounds that your body needs in small amounts to perform various functions. Some vitamins are essential, meaning that your body cannot make them and you have to get them from food or supplements. Other vitamins are non-essential, meaning that your body can make them from other substances. Vitamins are important for eye health because they help protect your eyes from damage caused by free radicals, which are unstable molecules that can harm your cells and DNA. Free radical
Post a Comment
Read more

Back Pain Uncovered: From Types and Causes to Treatment, Everything You Need to Know

  If you are one of the millions of people who suffer from back pain, you know how frustrating and debilitating it can be. Back pain can affect your quality of life, your productivity, your mood, and even your relationships. But what causes back pain, and what can you do to prevent or treat it? In this blog post, we will explore the most common types of back pain, their possible causes, and the best ways to prevent and cure them. By the end of this post, you will have a better understanding of your back pain, its causes and cures, and what you can do to improve your condition and your well-being. Let's get started! Types of Back Pain Back pain can be classified into two main categories: acute and chronic. Acute back pain is sudden and usually lasts for a few days or weeks. It can be caused by an injury, accident, muscle strain, or infection. Chronic back pain is persistent and lasts for more than three months. It can be caused by a variety of factors, such as aging, degenerative di
Post a Comment
Read more