# 2620
Behold, the killer of millions of people each and every year.
The lowly mosquito, carrier of dozens of diseases, infects hundreds of millions of people each year with everything from Malaria, to Dengue, to Yellow Fever, to West Nile, to Chikungunya.
On Saturday I relayed the story of how Chikungunya ended up in Northern Italy, and spread to nearly 300 people, all courtesy of one international traveler and the local Aedes mosquito population.
While we like to think of mosquito borne illnesses as being something found only in tropical climes, or of developing nations with poor public health infrastructures, the truth is mosquito borne illnesses are a threat almost everywhere in the world.
Europe and the United States are not immune.
A decade ago the West Nile Virus (WNV) appeared in the Western Hemisphere, first in New York City, seemingly out of the blue.
How WNV managed to find its way from its native Africa, to the United States is a matter of some conjecture. But in the span of a few short years, the virus has spread across all lower 48 states, into 7 Canadian Provinces, Mexico, and parts of the Caribbean.
From the USGS Factsheet on West Nile Virus
As you can see, the virus managed to spread rapidly in the first three years of introduction into the western hemisphere. In 2002, however, the range of the virus virtually exploded.
Most people infected with WNV experience mild, or sub-clinical symptoms. A small percentage develop WNV neuroinvasive disease (WNND), a form of encephalitis. For every serious presentation, there are probably 100 mild, or asymptomatic cases.
Of course, there are worse mosquito borne diseases than West Nile Virus. Diseases with greater morbidity and mortality. And they too pose a potential threat to the United States, and Europe.
Dengue Fever, for instance, is spread by the Aedes mosquito, and can be found in most tropical, and subtropical areas of the world. And Dengue fever can produce serious, sometimes fatal, illness in humans.
This from the CDC:
Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death.
<snip>
Dengue haemorrhagic fever (DHF) is a potentially deadly complication that is characterized by high fever, often with enlargement of the liver, and in severe cases circulatory failure.
There are serious concerns that over time Dengue may encroach into the more temperate climes, including the Southern United States and parts of Europe.
According to the CDC - As of 2005, dengue fever is endemic in most tropical countries of the South Pacific, Asia, the Caribbean, the Americas, and Africa.
And according to the WHO:
The incidence of dengue has grown dramatically around the world in recent decades. Some 2.5 billion people – two fifths of the world's population – are now at risk from dengue. WHO currently estimates there may be 50 million dengue infections worldwide every year.
In 2007 alone, there were more than 890 000 reported cases of dengue in the Americas, of which 26 000 cases were DHF.
Right now, portions of Northern Australia are experiencing a serious outbreak of Dengue fever, and there are concerns it may spread.
Mosquito virus health alert
Sarah Elks | December 31, 2008
Article from: The Australian
MOSQUITO-BORNE diseases are troubling health authorities in Queensland and NSW, with infection rates tipped to rise.
Far north Queensland is experiencing its worst outbreak of dengue fever in four years, sparking fears the disease may spread beyond the region.
At the same time, NSW health authorities are bracing for a large rise in the state's mosquito population, which will greatly increase the risk of Ross River virus and Barmah Forest virus in rural and coastal areas.
In Cairns, there have been 63 confirmed cases of dengue fever, which can cause fatigue, fever, rash, discomfort in the joints and muscles, and sometimes death.
Tropical Population Health Services senior director Brad McCulloch said the virus was introduced to Cairns by a traveller from Indonesia.
<snip>
Queensland Health says it is possible the mosquito might spread to the Northern Territory, Western Australia, southeast Queensland and NSW.
Meanwhile, NSW Health communicable diseases branch director Jeremy McAnulty said the beginning of January would be a high-risk time for Ross River virus and Barmah Forest virus in rural and coastal areas.
With millions of people traveling each year to regions of the world where Dengue, Malaria, Yellow Fever, Chikungunya, and other mosquito borne pathogens are common - the odds of their introduction into new regions increases.
As this CIDRAP article from 2007 points out, it can happen here.
Dengue fever expanding its foothold in Texas
Aug 9, 2007 (CIDRAP News) – Dengue fever is gaining a firmer foothold in southern Texas, putting residents at risk for the most dangerous form of the disease, dengue hemorrhagic fever (DHF), the Centers for Disease Control and Prevention (CDC) reported today.
A dengue outbreak in the Brownsville, Tex., area in 2005 involved 25 hospital cases, 16 of which were classified as DHF, the CDC reports in the Aug 10 issue of Morbidity and Mortality Weekly Report.
All of this is to point out that the vector, the common mosquito, is already in place throughout much of the world.
We keep their diseases at bay through a combination of efforts by public health departments, mosquito control boards, biologists, entomologists, engineers, and even the military.
It is a tenuous hold, we maintain, at best. We humans are badly outnumbered by mosquitoes.
Should we relax our control efforts, even briefly, many of these mosquito borne diseases would quickly expand into places where they haven't been a problem for decades.
Something to keep in mind as many local and state governments look for places to cut budgets in 2009.
Public health, and mosquito control, are two places that should be off limits.
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