Hello and welcome back fellows, when it comes to thinking about NTDs (shameless plug to previous posts), we’ve often discussed from the angle of parasites, but be not mistaken, for viruses too have a presence in this disease category. Prepare yourselves as we look at a fever that won’t have you dancing on a Saturday night!
Finally we’re discussing a simple named disease!
Dengue fever/breakbone fever (simple right?) is a viral disease caused by mosquitos of the Aedes genus. We’ve known about dengue fever since the 18th century; however it was only after the Second World War that the disease became a global problem. Gradual global mosquito distribution has generated an endemic in up to 110 countries with up to 528 million people annually infected.
When these mosquitos dine on our blood, the virus binds to and replicates within our white blood cells to manipulate our immune system. The result of this generates the fever aspect of the disease (this kind of fever won’t have you singing Peggy Lee’s classic). The next stage of infection includes: organ dysfunction, plasma leakage and severe gastrointestinal tract bleeding. The final stage, known as the recovery phase, is characterised by a decreased heart rate and severe itching.
For as terrible as dengue fever infection sounds, the fatality rate is only 1-5%. So with all of this in mind, what’s the big concern about dengue fever?
Well, the BIG CONCERNS are 1. Dengue fever is slowly overtaking malaria as the most common mosquito-borne disease and 2. Currently there are no commercial vaccines available, although some people may have something to say about that.
Pretty much a self-explanatory picture, simply put this fever might hold you tight to death!
At last! Hope is here?
French pharmaceutical giant Sanofi Pasteur has been investigating the candidate dengue fever vaccine called CYD-TDV (chimeric yellow fever virus tetravalent dengue vaccine vaccine) for over two decades, and in December 2015, CYD-TDV was given the green light in several countries including: Mexico, Brazil and the Philippines.
Marketed under the name Dengvaxia (subtle but blunt), this vaccine showed promise against the four known disease serotypes of the virus. However, this isn’t the magic formula to save us all from dengue virus. The vaccine has been shown to be 55-60% effective overall, being more favourable to some serotypes than others. Also the vaccine was seen to be more effective in those who had previously been infected with the virus and above the age of 9. Understanding this, the term “vaccine” for Dengvaxia seems inaccurate, particularly as considering the definition of vaccines, the effects of this “vaccine” seems to be more like an enhancement therapy. Hearing news like this may cause feelings of slight despondency; however optimism is on the horizon.
Emergence of a silver lining:
The NIAID (National Institute of Allergy and Infectious Diseases) has also tried their hand at investigating potential vaccines and in 2010, Phase I of clinical trials for the TV003 vaccine was launched .This vaccine is unique in that it serves as a tetravalent chimeric single dose vaccine. The results from the trials show that one dose of TV003 was sufficient enough to elicit a powerful antibody response to all four viruses. With this in mind, it was recently announced that Phase III of the clinical trial will soon commence in Brazil. Given the high prevalence rates of dengue fever in Brazil, the choice of location would prove to be ideal. Furthermore, producing TV003 has proven to cost less than $1 per dose, boosting hope in this candidate vaccine to be what could eliminate dengue fever once and for all.
Whilst the outright vaccine for dengue fever is still forthcoming, this news brings a sense of hope and assurance that things will turn around in an upward manner. In this, I find some joy in knowing that dengue fever’s end is sooner approaching than initially thought and thus another pivotal step in turning the NEGLECTED into RESPECTED.