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Today the World Health Organization released a progress report on the global battle against NTDs (Neglected Tropical Diseases) called:
Sustaining the drive to overcome the global impact of neglected tropical diseases - pdf, 8.23Mb
WHO reports `unprecedented progress’ against 17 neglected tropical diseases, but warns that Dengue is the fastest spreading vector-borne viral disease today, having increased 30-fold around the world in the past 50 years.
Some excerpts from the press release, then I’ll return with more on Dengue’s spread.
WHO heralds “new phase” in the fight against neglected tropical diseases
Sustained commitment key to reaching eradication and elimination targets by 2020
News release
16 January 2013 | GENEVA - WHO reports unprecedented progress against 17 neglected tropical diseases*, thanks to a new global strategy, a regular supply of quality assured, cost-effective medicines and support from global partners. The report Sustaining the drive to overcome the global impact of neglected tropical diseases reveals new momentum has shifted the world closer to the elimination of many of these conditions that take their greatest toll amongst the poor.
Report charts progress against NTDs and sets new targets
The publication charts progress in controlling, eliminating and eradicating these diseases. Two are targeted for global eradication, dracunculiasis (guinea worm disease) in 2015 and yaws in 2020. The report outlines six targets set for the elimination of five diseases in 2015 and a further 10 targets for nine diseases for 2020, either globally or in selected geographical areas.
“With this new phase in the control of these diseases, we are moving ahead towards achieving universal health coverage with essential interventions,” says Dr Margaret Chan, Director-General of WHO. “The challenge now is to strengthen capacity of national disease programmes in endemic countries and streamline supply chains to get the drugs to the people who need them, when they need them.”
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Other highlights of the report include:
- Eradication of guinea worm is in sight. WHO reports a reduction in reported cases of dracunculiasis (guinea-worm disease) with only 521 cases between January and September 2012 compared with 1006 confirmed cases for the same period in 2011 and of human African trypanosomiasis (sleeping sickness) to less than 7000 in 2011 from a high of 30 000 annual cases at the turn of the century.
- Rabies has been eliminated in several countries, with WHO eyeing regional elimination of this preventable disease by 2020. A new strategy which involves the early detection and use of antibiotics to treat Buruli ulcer has drastically reduced suffering and disability from this chronic and debilitating skin condition.
- An evaluation of WHO’s new strategy, which aims at eradicating yaws by 2020 using a new oral antibiotic treatment designed to replace those developed in the 1950s (which mainly centered on delivering injections of benzathine benzylpenicillin).
- Threats posed by dengue: in 2012, dengue ranked as the fastest spreading vector-borne viral disease, with an epidemic potential in the world, registering a 30-fold increase in disease incidence over the past 50 years. The world needs to change its reactive approach and implement sustainable preventive measures.
While it defines the concept of elimination and eradication, the report also analyzes some challenges that remain at country level. It emphasizes the need for national disease control programmes to improve coordination and integration. It highlights the need to strengthen human resources and to work with other sectors such as education, agriculture and veterinary public health in disease control programmes.
The explosive growth of Dengue around the world is well illustrated by the following graph from the World Health Organization. Almost unheard of outside of a few tropical ports in the early 1950s - driven by the post WWII travel boom - within 50 years it had spread to more than 60 countries.
What this graph doesn’t indicate is another doubling of dengue cases since 2007 and the spread to 125 countries (cite ECDC Epidemiological update Sept 2012). These numbers, while exceedingly large, are considered to be substantial undercounts of the real burden of the disease.
The WHO estimates that there are over 50-100 million cases of dengue worldwide each year and 3 billion people living in dengue endemic countries.
In order to spread, Dengue requires the right mosquito vector. And the two species best suited to transmit the virus are the Aedes aegypti and Aedes albopictus mosquitoes, which also can spread such diseases as West Nile, Malaria, Yellow Fever, and Chikungunya.
Map showing the distribution of dengue fever (red) and the distribution of the Aedes aegypti mosquito (cyan) in the world, as of 2006. – Credit Agricultural Research Service of the US Department of Agriculture.
Map showing the native habitat (blue) and recent spread (green) of the Aedes albopictus mosquito. --Credit Wikipedia
According to a 2009 report, as many as 28 states in the US have at least one of the these mosquito vectors, a factoid that has some epidemiologists worried that Dengue, Chikungunya, and Malaria could one day become threats in the United States.
There are 4 different serotypes of the Dengue Fever virus (DENV1, DENV2, DENV3 & DENV4), so a person can become infected several times over their lifetime. Usually, the first infection with a dengue virus results in the milder form of the illness, while more serious illness can occur with subsequent infections.
This fall, for the first time in their history – and In just over 6 weeks time - more than 2,000 cases of Dengue Fever have been reported in the Autonomous region of Madeira, an island with just over a quarter of a million residents, located 1000 km west of Portugal (see Epidemiological update: Outbreak of dengue in Madeira, Portugal).
Credit Wikipedia
In 2009, South Florida saw the introduction, likely through tourism, of the Dengue virus (see MMWR: Dengue Fever In Key West) after an absence of 6 decades.
And in 2010, Puerto Rico saw their worst epidemic in years (see MMWR: Dengue Epidemic In Puerto Rico) with nearly 21,000 cases and 31 fatalities.
To get a global view of the expansion of Dengue, we can use this interactive map that is a collaboration between the CDC and Healthmap.
Work is being done on a developing a Dengue vaccine, but early results have proven disappointing (see CIDRAP NEWS First dengue vaccine clinical trial finds low efficacy).
While not capable of spreading from person-to-person like a pandemic influenza virus, Dengue has readily shown its ability to hitch a ride on the local mosquito population to produce large epidemics.
For now, the only recourse is prevention. Destroying the places where mosquitoes breed, and taking steps to prevent getting bitten.
As with West Nile Virus, Chikungunya, Malaria, and every other mosquito-borne pathogen, the standard advice is:
