7 Fundamental Mistakes Not To Make About Dengue
For the scientist and the doctors it’s an easy catch, but the layman would think for example, that dengue can be treated with antibiotics like most known infections. Many feel dengue is a contagious deadly disease that can be transmitted from person to person; on the other hand some think they can get vaccinated against dengue. How many strains of the virus are there? Can they all cause disease? What is false and what is fact?
1.Dengue can be treated with antibiotics
Dengue is a tropical viral disease caused by the dengue virus. Dengue is transmitted principally by the mosquito A. aegypti, while organ donations and blood transfusion are also potential transmission routes. The Dengue virus is a single-stranded positive-sense RNA virus that replicate in monocytes, macrophages and dendritic cells. They belong to the family Flaviviridae. Other viruses of public health importance that belong to same family as the dengue virus include the Yellow Fever virus, Japanese Encephalitis virus and West Nile virus. A common mistake most people make is to think antibiotics are effective against viruses. Antibiotics, also known as antibacterial, are only effective against bacterial caused infections, they have no effect on viruses, hence cannot be used for the treatment of dengue infection. Treatment for dengue infection is mostly aimed at reliving symptoms; however dengue can be prevented by the control and/or elimination of infected mosquitoes.
2. All dengue infected persons show symptoms
About 4 to 6 days after exposure, infected persons see an increase in viral load (viremia) and onset of symptoms. First symptoms include exhaustion, headache, fever, joint and muscle pain, rash and swollen glands (lymphadenopathy); however more severe symptoms such as bleeding from the nose and gums, breathing difficulties, and vomiting blood may manifest about 3 to 7 days after the onset of primary symptoms. Symptoms vary according to age; younger children tend to have milder cases than older children and adults. However, most infected persons show no symptoms (asymptomatic) and clear the infection.
3. Dengue is contagious
A vector is an organism that spreads infection by carrying pathogens between other organisms referred to as host. Dengue is transmitted by human-to-mosquito-to-human cycle. The mosquito vector gets infected by feeding on a person with a high viremia. The infected mosquito in-turn transmits the virus by feeding on a healthy person. An infected female mosquito is capable of transmitting the virus to the next generation of mosquitoes. Dengue cannot be transmitted from one person to another (not contagious). The presence of a mosquito vector is necessary for the completion of the transmission cycle. In the absence of a vector it is impossible to transmit dengue via coughing or sneezing on another person, touching infected persons or contaminated surfaces, eating or drinking contaminated food and/or water sources, and sexual contact. Even though humans are the primary host, the virus circulates in other non-human primates.
4. The virus has a single strain (Serotype)
Unlike other members of the Flaviviridae family, such as the West Nile and Yellow Fever viruses which have single viral strains, Dengue Virus has four different strains referred to as serotypes (DEN-1, DEN-2, DEN-3, and DEN-4). Dengue serotypes which were formally geographically localized have now begun to experience changes in their distribution due to international travels. However, various world regions have seen unique serotype switches and the emergence and disappearance of certain serotypes as well. This has implicated the contribution of other factors as well rather than only international travels in the global distribution of dengue serotypes.
5. Some strains don’t produce illness
Once again, unlike some viral and bacterial counterparts that have strains that are harmless or are human commensals, all strains of dengue are capable of causing full spectrum disease. Recent studies also suggest that different clinical manifestations of the virus are associated to particular strains .
6. One strains induces cross immunity
Exposure to any one strain of dengue virus provides lifelong immunity from that strain, but not from the other strains. However, short term cross protection has be demonstrated by some researchers. Subsequent infection with a different strain other than the one initially contracted, increases risk of severe complication.
7. There is a Vaccine against Dengue
Unlike other viral infections such as hepatitis, typhoid fever, yellow fever, and polio that now have vaccines, there is no dengue vaccine. Since exposure to any one strain of dengue virus only provides lifelong immunity from that strain, there is need for a vaccine that can provide long-term protection against all virus strains. This, and the fact that secondary infection with another strain increases risk of severe complications, has been a major challenge for scientist. Regardless of the challenges dengue vaccine development has made good progress as there are vaccine candidates currently under trial. A study published in 2010 goes as far as forecasting that when introduced, 2.4 to 3.5 billion dengue vaccine doses would be needed in the first five years after introduction .
1) Tsai JJ et al (2009).” Effect of serotypes on clinical manifestations of dengue fever in adults”. J Microbiol Immunol Infect. 2009 Dec;42(6):471-8.
2) Amarasinghe A et al (2010). “Forecasting dengue vaccine demand in disease endemic and non-endemic countries”. Hum Vaccin. 2010 Sep 1;6(9). Epub ahead of print.