UEA Add Dengue Fever To The List

By Paul Homewood

 

h/t Dave Ward

 

https://www.uea.ac.uk/mac/comm/media/press/2014/August/climate-change-dengue

 

“Experts” from the UEA warn us that global warming will bring Dengue fever to Europe.

 

The UEA report:

The study used current data from Mexico, where dengue fever is present, and information about EU countries to model the likelihood of the disease spreading in Europe. They found that coastal regions around the Mediterranean and Adriatic seas, the Po Valley and North East Italy were most at risk.
Dengue fever is a tropical disease caused by a virus that is spread by mosquitoes, with symptoms including fever, headache, muscle and joint pain. Each year, dengue infects 50 million people worldwide and causes approximately 12,000 deaths – mostly in South-east Asia and the Western Pacific.
Because the mosquitoes that carry and transmit the virus thrive in warm and humid conditions, it is more commonly found in areas with these weather conditions. Dense populations and global travel are also associated with increasing the spread of the disease, which was observed in the last few decades.

 

 Prof Duane Gubler is one of the world’s leading experts on tropical diseases. In 1998, he authored one of the definitive studies on dengue fever, “Dengue and Dengue Hemorrhagic Fever”

 

ABSTRACT

Dengue fever, a very old disease, has reemerged in the past 20 years with an expanded geographic distribution of both the viruses and the mosquito vectors, increased epidemic activity, the development of hyperendemicity (the cocirculation of multiple serotypes), and the emergence of dengue hemorrhagic fever in new geographic regions. In 1998 this mosquito-borne disease is the most important tropical infectious disease after malaria, with an estimated 100 million cases of dengue fever, 500,000 cases of dengue hemorrhagic fever, and 25,000 deaths annually. The reasons for this resurgence and emergence of dengue hemorrhagic fever in the waning years of the 20th century are complex and not fully understood, but demographic, societal, and public health infrastructure changes in the past 30 years have contributed greatly. This paper reviews the changing epidemiology of dengue and dengue hemorrhagic fever by geographic region, the natural history and transmission cycles, clinical diagnosis of both dengue fever and dengue hemorrhagic fever, serologic and virologic laboratory diagnoses, pathogenesis, surveillance, prevention, and control. A major challenge for public health officials in all tropical areas of the world is to develop and implement sustainable prevention and control programs that will reverse the trend of emergent dengue hemorrhagic fever.

 

 The maps below show just how far the aegypti mosquitoes have spread in the Americas, but what is apparent is that they were equally well spread in the 1930’s. ( Also note the spread around the tip of S America – hardly a hot spot! Also Argentina).

 

A. aegypti distribution in the Americas during the 1930s and in 1970 and 1998.

Figure 1

 

 

Gubler even points out that dengue fever was discovered in Philadelphia back in 1780! As he says, the causes of this explosion of dengue are numerous and complicated, but he outlines them:

 

 

Factors Responsible for the Increased Incidence

The factors responsible for the dramatic resurgence and emergence of epidemic dengue and DHF, respectively, as a global public health problem in the past 17 years are complex and not fully understood. However, the resurgence appears to be closely associated with demographic and societal changes over the past 50 years. Two major factors have been the unprecedented global population growth and the associated unplanned and uncontrolled urbanization, especially in tropical developing countries. The substandard housing, crowding, and deterioration in water, sewer, and waste management systems associated with unplanned urbanization have created ideal conditions for increased transmission of mosquito-borne diseases in tropical urban centers.

A third major factor has been the lack of effective mosquito control in areas where dengue is endemic. The emphasis during the past 25 years has been on space spraying with insecticides to kill adult mosquitoes; this has not been effective  and, in fact, has been detrimental to prevention and control efforts by giving citizens of the community and government officials a “false sense of security”. Additionally, the geographic distribution and population densities of A. aegypti have increased, especially in urban areas of the tropics, because of increased numbers of mosquito larval habitats in the domestic environment. The latter include nonbiodegradable plastics and used automobile tires, both of which have increased dramatically in prevalence during this period.

A fourth factor responsible for the global emergence of dengue and DHF is increased air travel, which provides the ideal mechanism for the transport of dengue and other urban pathogens between population centers of the world. For instance, in 1994, an estimated 40 million persons departed the United States by air, over 50% of whom traveled for business or holiday to tropical countries where dengue is endemic. Many travelers become infected while visiting tropical areas but become ill only after returning home, resulting in a constant movement of dengue viruses in infected humans to all areas of the world and ensuring repeated introductions of new dengue virus strains and serotypes into areas where the mosquito vectors occur.

A fifth factor that has contributed to the resurgence of epidemic dengue has been the decay in public health infrastructures in most countries in the past 30 years. Lack of resources has led to a critical shortage of trained specialists who understand and can develop effective prevention and control programs for vector-borne diseases. Coincident with this has been a change in public health policy that placed emphasis on emergency response to epidemics by using high-technology mosquito control methods rather than on preventing those epidemics by using larval source reduction through environmental hygiene, the only method that has been shown to be effective.

A sixth factor was the ecologic disruption in the Southeast Asia and Pacific theaters during and following World War II created ideal conditions for increased transmission of mosquito-borne diseases, and it was in this setting that a global pandemic of dengue began.

Another factor was the discontinuation of the eradication programme in the Americas in the early 1970’s. In the 1950s, 1960s, and most of the 1970s, epidemic dengue was rare in the American region because the principal mosquito vector, Aedes aegypti, had been eradicated from most of Central and South America. The eradication program was discontinued in the early 1970s, and this species then began to reinvade the countries from which it had been eradicated. By the 1990s, A. aegypti had nearly regained the geographic distribution it held before eradication was initiated (Fig. 1). Epidemic dengue invariably followed reinfestation of a country by A. aegypti. By the 1980s, the American region was experiencing major epidemics of dengue in countries that had been free of the disease for 35 to 130 years. New dengue virus strains and serotypes were introduced (DEN-1 in 1977, a new strain of DEN-2 in 1981, DEN-4 in 1981, and a new strain of DEN-3 in 1994). Moreover, many countries of the region evolved from nonendemicity (no endemic disease) or hypoendemicity (one serotype present) to hyperendemicity (multiple serotypes present), and epidemic DHF emerged, much as it had in Southeast Asia 25 years earlier. From 1981 to 1997, 24 American countries reported laboratory-confirmed DHF.

In summary, demographic and societal changes, decreasing resources for vector-borne infectious disease prevention and control, and changes in public health policy have all contributed to increased epidemic dengue activity, the development of hyperendemicity, and the emergence of epidemic DHF.

http://cmr.asm.org/content/11/3/480.full

 

 

 

Nowhere in his analysis does Prof Gubler mention climate change, but don’t expect the UEA to tell you any of this.

But, hey, they’ve got models, so they must be right!