Dengue fever is an illness similar to flu symptoms but not upper respiratory system. It is caused by a virus transmitted by mosquitoes common.
The mosquitoes were found in all parts of the world, but several things are needed for the disease: humans susceptible, competent mosquito vectors (carriers), and a particular virus transmitted by mosquitoes.
Dengue fever is caused by four different viruses, which are closely related to each other. The disease is the same, the mosquito vector is the same, and the guest is the same. A person living in a tropical area where there are mosquitoes that transmit the disease can be four separate types of infection during their lifetime.
Usually we hear about the disease in the tropics where it is thriving. But dengue fever hit the United States for about 300 years. Fortunately eliminate malaria with dengue and yellow fever for more than 50 years. Remove it, not through the elimination of mosquitoes, they are still present, but by improving our standards of living, better housing, hot water systems, health care, control mosquitoes, in short, good health. In recent years we have seen a dramatic increase in dengue fever worldwide. The United States is vulnerable because the more dengue occurs in tropical destinations, tourism and business, more likely to be imported into the United States.
In the United States there are two types of mosquitoes that transmit dengue. Aegyti Aedes mosquito, which is a very efficient epidemic vector, is located mainly in southern Texas, southern Florida and parts of Arizona. Interestingly, in the desert, making places such as tropical oasis in Tucson, creating a good habitat for mosquitoes.
In terms of health is serious because it produces an acute febrile illness with prostration, in other words, an illness with fever that causes people to be in bed from one to six weeks, depending on the individual and the specific infection. There are no lasting effects associated with the disease. A small percentage of patients develop a severe form of the disease. Some patients develop a disease similar to viral encephalitis (which affects the brain) or internal bleeding. The severe form of the disease covers a wide range of conditions.
Dengue fever can have a tremendous economic impact on people because when a larger epidemic that affects thousands of people. When this happens, both the community and the medical system is paralyzed. It creates a significant burden to hospitals and clinics.
In summary, dengue fever is a very important. From the standpoint of economic impact, their impact can be measured by what we call "years of disability-adjusted life." The impact is of the same order of magnitude as that of many of the major infectious diseases of which we hear daily.
The main factor of spread is urbanization. As the tropical cities of the developing world have grown, the mosquito vector that has been there for many years, has expanded. Suddenly we are faced with large human populations living in intimate contact with the populations of mosquitoes. If the virus is no longer there, could be introduced. But in most cases the disease is already in the cities, so there are constant transmission, which increases the possibility of genetic change in the virus, which then increases the likelihood of the emergence of an epidemic strain.
If the largest factor is urbanization, it becomes more acute as the lack of effective control against mosquitoes. Combined with modern means of transport, this may be a potential disaster. Until the sixties the majority of the trip was by boat. We take weeks to cross the ocean. Beginning in the sixties, but accelerated in the seventies and eighties, people began to travel mostly by air. In the eighties and nineties we began to carry most of our raw materials by air. Modern transportation has become a vehicle for spreading the virus to urban centers around the world.
It is mostly confined to tropical regions. The sub-tropical regions like Texas and Florida may be susceptible. Here in the United States we are lucky for several reasons. First, we eliminated the disease in the fifties and sixties through improved living standards, through improved public health.
In addition, our population density is not as great in those areas of the United States where there are mosquitoes. Therefore, we have a combination of better health, lower mosquito populations, and smaller human populations, resulting in reduced risk of contact between humans and mosquitoes. Although in the United States have many virus imported from tropical areas, the local transmission is very limited and sporadic.
The virus mutates rapidly and has remained the same over time. As we learned more about the virus in the past 10 to 15 years, we have been able to use new technologies to study genetic changes that occur in viruses. We have found genetic changes, or as you called mutations, which influence the epidemic potential of these viruses. Therefore, it does not change as fast as the flu, but if it changes. Is not a static or monolithic, and we see that there are genetic changes that influence the transmission epidemic.
As cities grow tropical and human populations become larger, and we all four serotypes (groups) simultaneously circulating in those cities, the transmission increases. This increases the possibility of genetic changes in the virus, which in turn increases the likelihood that a new strain with increased fitness and greater epidemic potential is selected.
Dengue fever doesn't have the potential to adapt to cold weather. In the United States have had major epidemics of dengue and yellow fever as far north as Philadelphia and Boston. The reason this happened is that during the summer was hot enough to transmit infectious diseases. If diseases are introduced into an area where there is mosquito, transmission can occur.
In ancient times, the mosquito was in the states of the Gulf Coast, but each summer migrated upriver in boats or along the coast and returning to infect porteñas cities on rivers or oceans. This could happen today, but the northern cities do not have the conditions that allow mosquitoes to reproduce.
The mosquitoes breed mainly in water stored in containers. In ancient times we had no water piping systems. Stored water, which was ideal for the mosquitoes. Today we not only piping systems for water, we also have good drainage system. There are few places for mosquitoes to reproduce. Even when they are introduced to new places are not set there.
Right now we are in the midst of one of them. This began in the fifties, and has become progressively worse in over 50 years. I do not know how much worse will come, but I think most of the tropical world has been affected. Most of all four serotypes are present in all tropical cities. Do not expect to see outbreaks in the United States as the only vehicle we have here with wide distribution, is a very inefficient vector epidemic. Can transmit, but sporadically.
The pandemic is very bad because it is found throughout the tropical world. In the past there have also been epidemics of this disease. In the 1800s, these diseases are moving from region to region in sailboats, the mosquitoes were reproduced in the water stored in vessels, and is introduced as well as to new areas. Mosquitoes were transported in ships of a stinging iban sailor to another, and when those went down to earth, they introduced the virus to the mosquito population that lived there.
These pandemics were not as bad as the current one, and the reason is that cities today are much larger. We have a much larger population. We have jet planes rather than ships. Therefore pandemics we experience today are much worse than any we have experienced in the past.
These same factors will influence the influenza pandemic, whether this happens in the future. There are something like two billion people per year who get into a plane and travel somewhere, so the mechanisms are present to a rapid spread, not only dengue but other diseases such as influenza.
There is no vaccine for dengue fever. No drugs. There is much progress in both areas, and later I will talk about this again. There are very effective methods to control and prevent disease, and are simply controlling the mosquito. The mosquito is a highly domesticated insect that lives in intimate association with humans. Prefer to live in a house, played on a home prefer; prefer to rest at home. Therefore, if one removes the containers with a water storage can significantly reduce the mosquito population and thus reduce the likelihood of transmission. That is what we have done in an appropriate way in most tropical areas. Many places do not have a good control against mosquitoes, mainly because it is very difficult. The Gates Foundation (Gates Foundation) has funded a program called the Initiative for Pediatric Dengue Vaccine (The Dengue Vaccine Initiative), which focuses on supporting companies that are developing a vaccine against dengue, and possibly to distribute this populations at high risk. This program has great potential.
In the world we have a whole generation of people who have been bred since the sixties with the belief that essentially has little role to play regarding the fate of his health. There are drugs and vaccines. Hygiene and even taught in our schools. One of the most effective ways to prevent diseases like the flu is to wash hands. It is too easy today. One gets sick and goes to the doctor who gives a remedy, given an antibiotic. In the tropics, they give an injection. One is improved, and therefore there is no liability on the part of individuals.
We live in a society geared towards the crisis, do nothing until there is a crisis. We expect the epidemic to occur, and then try to answer it. People could very easily help public health officials with regard to this disease, you are controlling the disease in their own home environment. But many will not do, do believe that this is the responsibility of government.
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