Facts About Dengue
Over the past few years, Dengue fever, and severe Dengue have become major public health issues. Its prevalence is increasing. It affects billions of people around the world, many of them in low income and developing countries and there is no cure. Once some has contracted it there is little to be done except treatment of its symptoms and providing plenty of fluids.
It is an economic burden, both at the level of the family with a person affected by Dengue, and at the national level. Not to mention the emotional stress of parents with a child threatened by Dengue.
Prevention is a preferable option, but its success depends on economic, environment and cultural factors.
In many cases of vaccine-preventable diseases there is the principle of ‘herd immunity’ – a certain percentage of the population must be immunised for the vaccine to protect the whole of the population. Measles is an example. However, because of Dengue disease vectors this is not an approach that works.
Let’s take a look at what Dengue is, what is happening in a global context.
Dengue is a virus spread mainly by the same mosquito that spreads several other diseases such as chikungunya, yellow fever and Zika, Aedes aegypti. If someone who has been infected is bitten by an uninfected mosquito, that mosquito can be infected and spread the virus to its next victim. The mosquitoes are females who are gathering a blood meal for their young.
These mosquitoes lay their eggs, which develop into larvae, in standing water. That might be a discarded tin can or water collected inside discarded vehicle tyre. Anything in which water can stand, even tiny amounts, lets the mosquito thrive. In some countries, you will see a tub of water with small fish, guppies, which eat the larvae and reduces the number of mosquitoes.
So, basically, if there is still water, the mosquito can breed. One prevention measure is to remove such sources of water. In countries with monsoon rains that may be difficult to do thoroughly. And since people move around, if someone in the community doesn’t remove all standing water the threat remains. Such initiatives have to be a community effort.
Once contracted, Dengue presents flu-like symptoms and can develop into life-threatening severe Dengue. But in other cases, it may show as little more than a bout of sniffles and a cold that requires no medical attention. This can make it difficult to determine, without a full assay, whether some has had previous exposure to Dengue. Determining a previous infection accurately and quickly remains a challenge, an important point in the current discussion.
Like many viral diseases, a bout of Dengue can result in that person’s body producing specific antibodies which recognise the virus and generate the means to destroy that virus. But here’s the complication: Dengue consists of four different flavours, called serotypes. Infection by one type of Dengue may give one’s body the ability to fight off that specific type, but will not provide immunity against the other three varieties.
This has been a major challenge for those trying to produce a vaccine for Dengue. It is a difficult nut to crack.
Dengue fever is a severe, flu-like illness that affects infants, young children, and adults, but seldom causes death. Treatment consists of maintenance procedures and basically waiting for it to pass. Symptoms occur after an incubation period of 4–10 days after the bite from an infected mosquito and may produce a high fever (40°C/104°F) accompanied by at least two of the following symptoms: severe headache, pain behind the eyes, muscle and joint pains, nausea, vomiting, swollen glands or rash.
More dangerous is severe dengue, also calledhaemorrhagic fever, a potentially deadly complication due to plasma leaking (in which blood plasma leaks into surrounding tissues), fluid accumulation, respiratory distress, severe bleeding, or organ impairment. Warning signs occur 3–7 days after the first symptoms together with a decrease in temperature (below 38°C/100°F) and include: severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums, fatigue, restlessness and blood in vomit. The next 24–48 hours of the critical stage can be lethal; proper medical care is needed to avoid complications and risk of death.
For severe Dengue, proper medical treatment reduces the chance of fatality from around 20 percent to less than 0.5 percent.
Now let’s look at what has been happening with Dengue over the past few decades and why it is considered a global crisis.