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Dengue Fever Kills 204 in Taiwan

Posted by feww on December 16, 2015

Taiwan confirms nine new deaths from dengue fever; 204 killed since May

Heath authorities in Taiwan have confirmed nine new deaths from dengue fever, raising the death toll to 204 since May this year, a report quoted the country’s disease control agency as saying.

On average, the patients died within 6 days of showing symptoms, the agency reported.

The latest fatalities occurred in Kaohsiung city, south Taiwan. The victims, five male and four female, were aged between 55 and 82.

The total number of dengue fever cases has climbed to 41,947  with the majority recorded in Kaohsiung and Tainan, two of the largest cities in south Taiwan, said the report.

The outbreak is said to be the worst ever recorded. Last year, 15,732 cases and 28 deaths were reported, an eight-fold rise compared with previous numbers of about 2,000 cases annually.

Epidemiology of dengue [ncbi.nlm.nih.gov]

Dengue is currently regarded globally as the most important mosquito-borne viral disease. A history of symptoms compatible with dengue can be traced back to the Chin Dynasty of 265–420 AD. The virus and its vectors have now become widely distributed throughout tropical and subtropical regions of the world, particularly over the last half-century. Significant geographic expansion has been coupled with rapid increases in incident cases, epidemics, and hyperendemicity, leading to the more severe forms of dengue. Transmission of dengue is now present in every World Health Organization (WHO) region of the world and more than 125 countries are known to be dengue endemic. The true impact of dengue globally is difficult to ascertain due to factors such as inadequate disease surveillance, misdiagnosis, and low levels of reporting. Currently available data likely grossly underestimates the social, economic, and disease burden. Estimates of the global incidence of dengue infections per year have ranged between 50 million and 200 million; however, recent estimates using cartographic approaches suggest this number is closer to almost 400 million.

Introduction

Dengue is an acute mosquito-borne viral infection that places a significant socioeconomic and disease burden on many tropical and subtropical regions of the world. It is currently regarded as the most important arboviral disease internationally as over 50% of the world’s population live in areas where they are at risk of the disease, and approximately 50% live in dengue endemic countries.

Dengue virus

There are four distinct dengue virus serotypes, all of which originate from the family Flaviviridae and genus Flavivirus. The serotypes are termed DENV-1, DENV-2, DENV-3, and DENV-4, and infection with any of the four viruses results in lifelong immunity to that specific serotype. Each of the four serotypes has been individually found to be responsible for dengue epidemics and associated with more severe dengue. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3753061/

Transmission of the Dengue Virus [CDC]

With a newly-obtained fiery red blood meal visible through her transparent abdomen, the now heavy female Aedes aegypti mosquito took flight as she left her host’s skin surface. Photo Credit: James Gathany/ CDC

Dengue is transmitted between people by the mosquitoes Aedes aegypti and Aedes albopictus, which are found throughout the world.  Insects that transmit disease are vectors.  Symptoms of infection usually begin 4 – 7 days after the mosquito bite and typically last 3 – 10 days.  In order for transmission to occur the mosquito must feed on a person during a 5- day period when large amounts of virus are in the blood; this period usually begins a little before the person become symptomatic.  Some people never have significant symptoms but can still infect mosquitoes.  After entering the mosquito in the blood meal, the virus will require an additional 8-12 days incubation before it can then be transmitted to another human. The mosquito remains infected for the remainder of its life, which might be days or a few weeks.

In rare cases dengue can be transmitted in organ transplants or blood transfusions from infected donors, and there is evidence of transmission from an infected pregnant mother to her fetus.  But in the vast majority of infections, a mosquito bite is responsible.

In many parts of the tropics and subtropics, dengue is endemic, that is, it occurs every year, usually during a season when Aedes mosquito populations are high, often when rainfall is optimal for breeding.  These areas are, however, additionally at periodic risk for epidemic dengue, when large numbers of people become infected during a short period.  Dengue epidemics require a coincidence of large numbers of vector mosquitoes, large numbers of people with no immunity to one of the four virus types (DENV 1, DENV 2, DENV 3, DENV 4), and the opportunity for contact between the two.  Although Aedes are common in the southern U. S., dengue is endemic in northern Mexico, and the U.S. population has no immunity, the lack of dengue transmission in the continental U.S. is primarily because contact between people and the vectors is too infrequent to sustain transmission.

Dengue is an Emerging Disease

The four dengue viruses originated in monkeys and independently jumped to humans in Africa or Southeast Asia between 100 and 800 years ago.  Dengue remained a relatively minor, geographically restricted disease until the middle of the 20th century.  The disruption of the second world war – in particular the coincidental transport of Aedes mosquitoes around the world in cargo –  are thought to have played a crucial role in the dissemination of the viruses.  DHF was first documented only in the 1950s during epidemics in the Philippines and Thailand.  It was not until 1981 that large numbers of DHF cases began to appear in the Carribean and Latin America, where highly effective Aedes control programs had been in place until the early 1970s.

Dengue is endemic in at least 125 countries

Dengue is endemic in more than 125 countries in Asia, the Pacific, the Americas, Africa, and the Caribbean.

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