Dengue Fever Facts & Worksheets

Dengue fever is a viral ailment spread to people by infected mosquito bites. The principal carriers of the infection are Aedes aegypti mosquitoes and, to a minor extent, Aedes albopictus mosquitoes.

See the fact file below for more information on Dengue fever, or you can download our 33-page Dengue worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

OVERVIEW

• Dengue fever is a mosquito-borne viral illness that has recently spread to all WHO areas. Furthermore, female mosquitoes, primarily Aedes aegypti, transmit the dengue virus.
• These mosquitoes also transmit the chikungunya, yellow fever, and Zika viruses. Dengue fever is found throughout the tropics, with local differences in risk determined by climate, socioeconomic, and environmental factors.
• For instance, dengue can lead to a variety of illnesses. Infected individuals may experience mild flu-like symptoms or severe sickness. Even though it’s less often, some people experience severe dengue, which can lead to various issues, including severe bleeding, organ damage, and plasma leakage.
• Throughout dengue outbreaks in Thailand and the Philippines in the 1950s, severe dengue was already identified. Dengue fever has become a prominent cause of illness and death in children and adults in most Asian and Latin American nations today.
• Additionally, four different but closely related serotypes of the Flaviviridae family virus cause dengue, the disease’s primary cause (DENV-1, DENV-2, DENV-3, and DENV-4). Immunization against that serotype is thought to last a lifetime following infection recovery. 
• Cross-immunity to the other serotypes is only transitory and partial following recovery. The risk of acquiring severe dengue is increased by secondary infection (secondary infection) by various serotypes.
• The four different serotypes of the dengue virus have diverse epidemiological trends. These can circulate together within a region, and all four serotypes are hyperendemic in several countries. Furthermore, dengue poses a grave threat to national and international economies as well as public health.
• When susceptible vectors are available in these new regions, there is the possibility of local transmission being created because DENV(DENgue Virus)  is regularly spread from one place to another through infected travelers.
• Furthermore, almost half of the world’s population is at risk due to the sharp rise in dengue incidence worldwide. Although between 100 and 400 million infections are thought to occur annually, more than 80% are often minor and asymptomatic.

GLOBAL IMPACT

• In recent decades, dengue cases have drastically increased across the world. Dengue cases go unreported since many are asymptomatic, moderate, and self-managed. In a lot of situations, other febrile disorders are mistakenly identified.
• There are 390 million dengue virus transmissions per year, according to one modeling estimate (95% credible interval: 284-528 million), of whom 96 million (67-136 million) show clinical symptoms (with any severity of disease).
• According to a different study on the incidence of dengue, 3.9 billion people worldwide could contract dengue viruses. Although there is a risk of infection in 129 nations, Asia bears the most of the burden.
• Over the past 20 years, from 505,430 cases in 2000, including over 2.4 million in 2010 and 5.2 million in 2019, there has been an over 8-fold increase in dengue cases reported to the WHO.
• Between 2000 and 2015, the number of reported deaths grew from 960 to 4032, mainly impacting younger age groups.
• Additionally, it appears that both the overall number of cases and reported deaths declined in the years 2020 and 2021. The data is not yet complete, and the COVID-19 pandemic may have made it more difficult for countries to disclose cases.
• A change in national policies to record and transmit dengue to the Ministries of Health and the WHO is one explanation for the overall alarming rise in cases of counts over the last 20 years. However, it also shows that the government is aware of the problem, making it necessary to record the burden of dengue disease.

DISTRIBUTION AND OUTBREAKS

• Only nine nations had severe dengue epidemics before 1970. Within the WHO regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia, and the Western Pacific, the illness is currently endemic in more than 100 countries. 
• The Americas, South-East Asia, and Western Pacific are the most severely impacted regions, with Asia accounting for over 70% of the worldwide disease load. As the disease enters new areas, such as Europe, the number of cases rises, but there are also explosive outbreaks.
• Since local transmission was first documented in France and Croatia in 2010, and imported cases were found in three other European nations, there is now a threat of a dengue outbreak.
• Over 2,000 cases of dengue were reported in the Portuguese Madeira Islands in 2012, while imported instances were found in Portugal’s mainland and ten other European nations. Few European countries now report autochthonous cases yearly.
• In 2019, there were more dengue cases than had ever been recorded globally. All areas were affected, and Afghanistan experienced its first dengue transmission.
• Over 25,000 of the 3.1 million cases recorded in the American region were considered severe. Despite this concerning number of infections, there were fewer dengue-related deaths than the year before. In Asia, Bangladesh (101,000 cases), Malaysia (131,000 cases), the Philippines (420,000 points), and Vietnam (320,000 cases) also reported high numbers of patients.
• Additionally, there have been numerous cases reported in Asia’s Bangladesh (101,000), Malaysia (131,000), Philippines (420,000), and Vietnam (320,000).
• There were reports of an increase in dengue cases in Bangladesh, Brazil, the Cook Islands, Ecuador, India, Indonesia, the Maldives, Mauritania, Mayotte (Fr), Nepal, Singapore, Sri Lanka, Sudan, Thailand, Timor-Leste, and Yemen in 2020. Brazil, India, Vietnam, the Philippines, the Cook Islands, Colombia, Fiji, Kenya, Paraguay, Peru, and the Reunion Islands are still experiencing dengue in 2021.
• The COVID-19 epidemic is putting an enormous strain on the world’s health management and care systems. As cases rise in multiple countries and urban populations are most at risk for both diseases, the WHO has stressed the necessity of continuing efforts to prevent, diagnose, and treat vector-borne illnesses like dengue as well as other arboviral infections during this pandemic. The combined effects of COVID-19 and dengue outbreaks could be disastrous for communities at risk.

TRANSMISSION: Through Mosquito Bites

• The virus spreads to people when infected female mosquitoes, mainly the Aedes aegypti mosquito, bite them; although other Aedes genus species can act as vectors, Ae. aegypti is the primary contributor.
• The mosquito midgut is where the virus replicates after feeding on a human with DENV infection before spreading to secondary tissues like the salivary glands. The extrinsic incubation period refers to the time between consuming the virus and actually transmitting it to a new host (EIP). The amplitude of daily temperature changes, the virus genotype, and the initial viral concentration are a few examples of variables that affect the extrinsic incubation period and can affect how long it takes a mosquito to transmit a virus. Moreover, the mosquito can continue to spread viruses for the remainder of its life after becoming infected.

TRANSMISSION: Through Human-to-Mosquito

• Mosquitoes can pick up the DENV virus from individuals infected with it. These can include persons with symptoms of dengue infection, those who are pre-symptomatic but have not yet developed symptoms, and those who are entirely well (they are asymptomatic). 
• Additionally, human-to-mosquito transmission can take place up to 2 days before the onset of symptoms and up to 2 days after the fever has subsided. High levels of the patient’s viremia and fever favorably correlate with the likelihood of mosquito infection; on the other hand, high levels of DENV-specific antibodies negatively correlate with the risk of mosquito infection.

VECTOR ECOLOGY

• The primary DENV vector is thought to be the Aedes aegypti mosquito. It could reproduce in naturally occurring containers like tree holes and bromeliads, but today it has adapted well to urban habitats and primarily reproduces in man-made containers.
• Ae. aegypti feeds during the day; its peak biting times are in the early morning and just before sunset in the evening. Female Ae. aegypti regularly feeds several times between each egg-laying period, resulting in concentrations of infected people.

DISEASE CHARACTERISTICS: Signs and Symptoms

• Dengue can emerge as a severe, flu-like sickness that affects newborns, young children, and adults but seldom results in death, even though most patients are asymptomatic or exhibit minor symptoms.
• After an incubation period of 4–10 days following the bite by an infected mosquito, symptoms typically last for 2–7 days. Dengue is divided into two main categories by the World Health Organization: mild dengue and severe dengue.
• The sub-categorization of dengue with or without warning signals is intended to aid medical professionals in prioritizing patients for hospital admission, guaranteeing close supervision, and lowering the risk of contracting the more severe dengue.
• Dengue should be suspected when a high fever (40°C/104°F) is accompanied by any of the following symptoms during the febrile period (2–7 days).
  • terrible headache
  • suffering from eye pain
  • joint and muscle discomfort
  • nausea
  • vomiting
  • enlarged glands
  • rash
• Typically, a patient enters the critical period 3–7 days following the start of their sickness. A small percentage of patients may experience a dramatic deterioration of symptoms during the critical phase’s first 24 to 48 hours. Due to plasma leakage, fluid accumulation, respiratory difficulties, severe bleeding, or organ dysfunction, severe dengue is a potentially deadly consequence.
• Doctors should keep an eye out for the following warning signs:
  • acute stomach discomfort
  • continual vomiting
  • quickly breathing
  • bleeding nose or gums
  • fatigue
  • restlessness
  • an enlarged liver
  • blood in the stool or vomit

DIAGNOSTICS

• In the early stages of illness, the virus may be isolated from the blood. There are various reverse transcriptase-polymerase chain reaction (RT-PCR) techniques available, and these are considered the best. To execute these examinations, staff members need specialized tools and training.
• By detecting anti-dengue antibodies, serological techniques like enzyme-linked immunosorbent tests (ELISA) can determine whether a current or previous infection existed. IgM antibodies can be found around a week after infection and last for about three months. IgM indicates a recent DENV infection when it is present. 
• The body retains IgG antibody levels for years, and they take longer to develop. IgG indicates a prior infection because it is present.

TREATMENT

• Dengue fever has no specific therapy. Patients should relax, drink plenty of water, and consult a doctor. Patients may be sent home, for in-hospital treatment, or require emergency care and an urgent referral depending on the clinical symptoms and other factors.
• To manage the symptoms of muscle soreness and fever, supportive treatments such as painkillers and fever reducers can be used.

• Nevertheless, for severe dengue, medical care provided by doctors and nurses familiar with the disease’s symptoms and course can save lives and lower mortality rates to less than 1% in most countries.

Dengue Fever Worksheets

This fantastic bundle includes everything you need to know about Dengue fever across 33 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Dengue, a viral illness that is transmitted to humans through the bite of infected mosquitoes.

Complete List of Included Worksheets

Below is a list of all the worksheets included in this document.

• Dengue Facts
• Good or Bad?
• The Symptoms
• The Matrix of Dengue
• Dengue vs. Covid-19
• Know it, Then Find it!
• The Deadly Mosquito
• Major Outbreak
• Prevention and Control
• Be Healthy, Be Aware!
• InfoDengueraphic

Frequently Asked Questions

What is dengue?

Dengue is a viral illness transmitted by the bite of infected mosquitoes. It causes flu-like symptoms such as high fever, joint and muscle pain, headache, and rash. In severe cases, it can lead to dengue hemorrhagic fever, which can be fatal if not treated promptly.

What are the symptoms of dengue?

The symptoms of dengue usually appear 3 to 14 days after a mosquito bite. The most common symptoms include high fever, severe headache, joint and muscle pain, and a rash. Other symptoms may include nausea, vomiting, and abdominal pain. In extreme cases, bleeding may occur from the gums, nose, or under the skin.

How is dengue transmitted?

Dengue is transmitted by the bite of infected mosquitoes, specifically Aedes aegypti and Aedes albopictus mosquitoes. The mosquitoes become infected with the dengue virus after biting an infected person and then transmit the virus to others through subsequent bites.

How can dengue be prevented?

Dengue can be prevented by avoiding mosquito bites, which can be done by wearing long sleeves and pants, using mosquito nets, and applying mosquito repellent. Eliminating standing water where mosquitoes breed, such as in containers and tire piles, can also help reduce the risk of dengue transmission.

How is dengue treated?

There is no specific treatment for dengue. Instead, the focus is on relieving symptoms and managing complications. Treatment may include pain relievers, rest, and plenty of fluids. In severe cases, hospitalization may be necessary for close monitoring and treatment of complications. In such cases, early recognition and prompt medical attention are critical for a successful outcome.

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