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article imageDengue fever's frightening rise associated with climate change

By Karen Graham     Sep 30, 2014 in Health
Health authorities in China and Southeast Asia are warning travelers to be particularly careful when traveling to Guangdong Province in China, Singapore, Taiwan and Malaysia. Dengue fever is rampant in these areas, with over 80,000 cases reported to date.
In South China's Guangdong Province, 1,152 new cases of Dengue fever were reported on Sunday, bringing the total number of infected people to 11,867 confirmed cases. In Guangdong Province alone, there have been four deaths reported, the latest on Sunday, according to the provincial health and family planning commission.
Government health authorities are saying the Dengue fever outbreak is believed to be the worst seen in 20 years. Increased temperatures and rainfall are being blamed on the increase in the number of cases of the disease because the mosquito population is fives times higher than normal.
The Centre for Health Protection's controller, Dr Leung Ting-hung said a British health care worker died this week after contracting Dengue fever on Sumatra. He also confirmed that 68 imported cases of the fever have been reported in Hong Kong. Leung said the number of cases is expected to increase for at least another month as the high heat and heavy rains continue, making breeding grounds for mosquitoes more available.
At least 20 governmental departments in Hong Kong have been coordinating their efforts on reducing the mosquito populations. A third round of "mosquito control" measures will be taking place from mid-October to mid-November this year. The Food and Environmental Hygiene Department is in charge of the actual pest control operations, and has warned people to get rid of any standing water.
Standing water, even shallow pools of stagnant water are potential breeding grounds for the Aedes mosquitoes. People are being reminded that the eggs of the Aedes mosquito can remain viable, surviving drought conditions. All they need to hatch is a little dampness.
Dengue fever has become a major international health problem
The global incidence of Dengue fever has grown significantly in the past decade to the point that half the world's population is now at risk. The disease was first recognized in the 1950's in the Philippines and Thailand. Today, the virus affects most all Asian and Latin American countries, and has become the leading cause of hospitalization and deaths in children in these areas.
The World Health Organization (WHO) estimates that there are 50-100 million cases of Dengue fever annually around the globe. Before the 1970s, Dengue fever was only found in nine countries. Today, Dengue fever is endemic in over 100 countries, including Africa, Central and South America, the Eastern Mediterranean, South-east Asia and the Western Pacific.
To emphasize how fast the disease has spread worldwide, WHO used official data submitted by member nations to compile the following statistics:
1. 2008: 1.2 million cases worldwide (Americas, South-East Asia, Western Pacific).
2. 2010: 2.3 million cases worldwide (Same regions as above).
3. 2013: 2.35 million cases in the Americas alone.
Global climate change and the increase in mosquito-borne diseases
There have been a number of studies conducted over the past several years that look at mosquito-borne diseases and their incidence and spread in relation to increased temperatures and rainfall amounts on a global scale. It's important to note that for many countries, particularly European, Mediterranean and several countries in the Northern Hemisphere, the incidence of mosquito-borne disease has been almost non-existent.
Malaria, Dengue fever, Lyme disease (a tick-borne viral disease) and other diseases are usually associated with warm, humid regions of the world. Making forecasts based on non-existent models is pure speculation. But with little else to go on, scientists can only say the "exact incidence of a mosquito-borne disease is dependent on several factors."
For example, in August the Daily Mail reported on a study done by researchers at University of East Anglia (UEA). The study was based on data for the Dengue fever in Mexico. Using climate variables like temperature, humidity and rainfall, along with other factors, such as the occurrence of the viral illness. They then collected climate data on European countries and were able to model which nations were most at risk.
Baseline cases of Dengue Fever in Europe
Baseline cases of Dengue Fever in Europe
The study was published in the journal BMC Public Health. "Our study has shown that the risk of dengue fever is likely to increase in Europe under climate change, but that almost all of the excess risk will fall on the coastal areas of the Mediterranean and Adriatic seas and the North Eastern part of Italy, particularly the Po Valley," said lead researcher Professor Paul Hunter.
Projected cases of Dengue Fever in Europe by 2040.
Projected cases of Dengue Fever in Europe by 2040.
Other studies, in the U.S. and elsewhere, are just as inconclusive, but yet they do tell us some important facts. Number one, yes, Dengue fever is on the rise, globally, as is the number of cases of malaria and other insect-vector diseases. In most cases this is because of warmer temperatures that are prolonged, as well as increased rainfall and humidity.
May showing U.S. vector range for Dengue fever and number of suspected cases.
May showing U.S. vector range for Dengue fever and number of suspected cases.
Number two, and this is something most of the studies have been recommending, is updated mosquito prevention programs. Many states and communities in the U.S. have already developed preparedness measures to address the spread of infectious diseases due to climate change. Again, the most frequent recommendation is increasing surveillance of mosquito-borne diseases. This is also what is recommended by the UEA researchers in their study.
More about Dengue fever, aedes mosquito, globel distribution, south china, Global warming
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