Latest Dengue Fever Outbreaks

Brazil reported record number of dengue cases in 2015

Brazil registered 1.6 million cases of dengue fever in 2015, up from the previous record of 1.4 million cases in 2013, the Health Ministry reported.

• Peak incidence of dengue infection rates occurred in April, with 229.1 cases for every 100,000 people.

• Dengue-related fatalities reached 863 in 2015, also a record high.

• Two other diseases transmitted by the Aedes mosquito, the Zika virus and chikungunya fever, are also spreading rapidly across the country.Transmission of the Dengue Virus [CDC]

Cambodia

Cambodia reported 15,412 cases of dengue fever in 2015, a rise 314 percent from the previous year.

• “The incident rate was 93.5 cases out of 100,000 people,” said a senior health official. “Some 71 percent of the patients were children aged between 5 and 14 years old.”

• At least 38 children were killed by the infection in 2015, a rise of 81 percent.

Taiwan

Tiwan reported 43,259 cases of dengue infection in 2015, which killed at least 212 people across the island, the worst outbreak on record.

• In 2014, the country reported 15,732 cases, compared with the previous annual average of 2,000 cases.

Paraguay

Authorities and citizens alike in the Latin American country are concerned that another epidemic of dengue fever could “easily start up following December’s rains, which in Asuncion flooded entire neighborhoods and forced some 100,000 residents to evacuate their homes,” the Paraguayan Health Ministry said.

More than 150,000 people were infected in a 2013 dengue epidemic, which killed 252 people,  Agencia EFE reported.

Stats from WHO

• Cases across the Americas, South-East Asia and Western Pacific exceeded 1.2 million in 2008 and over 3 million in 2013 (based on official data submitted by Member States). Recently the number of reported cases has continued to increase. In 2013, 2.35 million cases of dengue were reported in the Americas alone, of which 37 687 cases were of severe dengue.

• Not only is the number of cases increasing as the disease spreads to new areas, but explosive outbreaks are occurring. The threat of a possible outbreak of dengue fever now exists in Europe and local transmission of dengue was reported for the first time in France and Croatia in 2010 and imported cases were detected in 3 other European countries. In 2012, an outbreak of dengue on the Madeira islands of Portugal resulted in over 2000 cases and imported cases were detected in mainland Portugal and 10 other countries in Europe.

• In 2013, cases have occurred in Florida (United States of America) and Yunnan province of China. Dengue also continues to affect several South American countries, notably Costa Rica, Honduras and Mexico. In Asia, Singapore has reported an increase in cases after a lapse of several years and outbreaks have also been reported in Laos. In 2014, trends indicate increases in the number of cases in the People’s Republic of China, the Cook Islands, Fiji, Malaysia and Vanuatu, with Dengue Type 3 (DEN 3) affecting the Pacific Island countries after a lapse of over 10 years. Dengue was also reported in Japan after a lapse of over 70 years. In 2015 an increase in the number of cases was reported in Brazil and several neighbouring countries. The Pacific island countries of Fiji, Tonga and French Polynesia have continued to record cases.

• [At least] 500 000 people with severe dengue require hospitalization each year, a large proportion of whom are children. About 2.5% of those affected die.

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/

Female Aedes aegypti mosquito

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

 

Transmission of the Dengue Virus [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.

Related Links

• Top Emerging Diseases Likely to Cause Major Epidemics December 12, 2015
• ZIKV – Emerging Virus May Cause Severe Birth Defects December 4, 2015
• Dengue Fever Kills 204 in Taiwan  December 16, 2015
• State of Emergency Declared in East Java  January 26, 2015
• Dengue Fever Outbreak Prompts State of Emergency in Brazil City  January 21, 2013
• State of emergency in Marshall Islands as dengue outbreak spirals  October 29, 2011
• Chikungunya Makes West Nile Look Like Nappy Rash  September 19, 2009