Yellow Fever: Epidemiology and Virus Characteristics

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Questions and Answers

What is the primary transmission method of yellow fever?

Transmission through contaminated water

Bite of Aedes mosquitoes (correct)

Direct contact with infected individuals

Airborne transmission through respiratory droplets

Which of the following is NOT a characteristic of flaviviruses from Group B?

Marked antigenic cross-reactivity among the viruses

Rapid virus isolation is an effective diagnostic method

Difficult serological diagnosis in high endemic areas

All diseases are predominantly transmitted by ticks (correct)

Which statement about the epidemiological forms of yellow fever is correct?

Jungle form is transmitted only between humans.

Urban/rural form commonly involves infected monkeys.

Both forms primarily transmit through body fluids.

The jungle form results in accidental human infection. (correct)

What is the incubation period of yellow fever in humans?

3-6 days (maximum 10 days) Signup and view all the answers

What is the consequence of an attack of yellow fever regarding immunity?

Complete immunity lasting a lifetime Signup and view all the answers

What is the recommended duration for quarantine for individuals without valid yellow fever vaccination certificates?

6 days Signup and view all the answers

Which of the following is NOT a method used to control yellow fever?

Vaccination of pets Signup and view all the answers

Which region reported the highest number of dengue fever cases according to the Sudanese Ministry of Health?

North Kordofan Signup and view all the answers

What characterizes dengue fever compared to dengue haemorrhagic fever?

Dengue fever is generally a non-fatal illness without hemorrhagic phenomena. Signup and view all the answers

After vaccination, how long does it take for a yellow fever vaccination certificate to become valid?

10 days Signup and view all the answers

What is the total mortality rate reported for dengue fever cases on 22 November in Sudan?

23 deaths Signup and view all the answers

Which of the following statements about dengue fever and dengue haemorrhagic fever is correct?

Dengue fever is generally non-fatal, while dengue haemorrhagic fever occurs with significant mortality. Signup and view all the answers

What is the overarching effect of dengue fever in terms of population exposure?

It occurs in more than 100 countries worldwide. Signup and view all the answers

What is the primary mode of transmission for Dengue fever?

Bite of Aedes aegypti Signup and view all the answers

Which of the following symptoms is NOT typically associated with Dengue fever?

Chest pain Signup and view all the answers

At what age is the incidence of haemorrhagic manifestations from Dengue fever most common?

Under 15 years old Signup and view all the answers

What is the appropriate control measure for Dengue fever?

Vector control Signup and view all the answers

Which organism is responsible for causing Dengue fever?

Dengue virus (serotypes 1-4) Signup and view all the answers

Which of the following is NOT a component of the laboratory diagnosis for Dengue fever?

Organ biopsy Signup and view all the answers

How long does immunity last after a Dengue fever infection?

1 year Signup and view all the answers

Which regions are predominantly affected by Dengue fever outbreaks?

South East Asia and the tropics Signup and view all the answers

Study Notes

Viral Haemorrhagic Fever

Viral haemorrhagic fevers are a group of infectious diseases caused by arboviruses. These viruses are often transmitted by mosquitoes.
A characteristic symptom of this group of diseases is bleeding from all natural body orifices.
Flaviviruses (Group B) arboviruses cause a range of diseases, including yellow fever, dengue fever, Japanese B encephalitis, Rift Valley Fever, Kyasanur Forest disease and West Nile Fever.
The high antigenic cross-reactivity of the viruses makes serological diagnosis difficult, especially in highly endemic areas.
Virus isolation is the definitive diagnostic method for these diseases.

Yellow Fever

Yellow fever is an acute infectious disease with a sudden onset and variable severity.
The disease is caused by a virus transmitted by mosquitoes.
The disease is characterized by fever, jaundice, haemorrhagic manifestations and albuminuria.
The incubation period in humans is 3 to 6 days (maximum 10 days).
Yellow fever is internationally notifiable.
Fatality rates vary from 5 to 40%.
An attack of yellow fever provides life-long immunity.
Yellow fever mainly affects South America and tropical Africa (between 15° N and 100° S).
The reservoir hosts for the virus are humans and monkeys.
Yellow fever transmission occurs by the bite of Aedes spp mosquitoes.
The control of yellow fever involves isolation of suspected cases, vector control to target breeding sites, using insecticides and vaccination.
A vaccination certificate is valid for 10 years following vaccination.

Two epidemiological forms of Yellow Fever,

Jungle fever (Sylvan): transmission between monkeys, and accidental human infection.
Urban/Rural: transmission between humans (clinical or subclinical cases).

Laboratory Diagnosis of Yellow Fever

Virus isolation from blood samples taken during the early stages (up to the 4th day) of the illness is used to diagnose yellow fever.

Dengue Fever in Sudan

Sudan has seen a large outbreak (3,326 cases) of dengue fever in November 2022, with 23 deaths.
North Kordofan is the most affected region, followed by West Kordofan.
Other areas of Sudan are also reporting cases, such as North Darfur.
Dengue fever and dengue hemorrhagic fever are prevalent in over 100 countries, especially in the tropics and subtropics. It affects over 2.5 billion people.

Dengue fever, Types and Symptoms

Two types of dengue occur:
- Dengue fever is non-fatal and characterized by fever, severe myalgia and joint pains. The illness is febrile.
- Dengue Hemorrhagic fever (DHF) is commonly in children; it involves haemorrhagic phenomena and often results in significant mortality.
Dengue fever is a significant illness creating discomfort, but it is usually not fatal.
Symptoms usually occur in adults, and recovery might be prolonged even after the fever retreats in a week or so. Specific clinical presentations involve:
- Severe muscle pains
- Joint pain
- Lymph node enlargement
- Skin rash (resembling measles) on the 4th day
DHF is typically observed in children but is sometimes observed in adults
Features of DHF include:
- Fever
- Haemorrhagic manifestation
- Liver enlargement

Dengue Fever - Key Facts

Dengue fever has a wide distribution in the tropics, with significant hemorrhagic epidemics primarily in Southeast Asia
The causative organism is Dengue virus (serotypes 1-4).
Humans are the reservoir
Transmission occurs through the bite of Aedes aegypti mosquitoes.
Vector control is a key element in preventing the spread of dengue fever.
The incubation period is 2 weeks.

Host Factors in Dengue

Haemorrhagic manifestations are most frequent in children under 15 years of age.
While peaks incidence are observed in the 3-6 age group, haemorrhagic dengue fever (DHF) can occur in all age groups.
Infection confers immunity for approximately one year.

Laboratory Diagnosis of Dengue

Virus isolation from the blood (collected in early stages of the illness is used): Serotypes can be identified.

Dengue Fever Control measures

Vector control, active disease surveillance and community efforts for behavioural change, emergency preparedness combined with capacity building and training, are crucial for controlling its spread.

Kyasanur Forest Fever

Kyasanur Forest Fever emerged after people cleared forests for grazing lands.
Disease was first observed in monkeys in 1955.
Humans started to die from haemorrhagic fever in 1957
The case fatality rate was 20%.
The virus that causes this fever is transmitted by ticks from cattle but the source of the virus still remains unknown, although monkeys were also victims.

Lassa Fever

Lassa Fever was first identified in Nigeria in 1969 but may have been present for longer, possibly confused with other diseases like malaria or yellow fever.
It is now endemic in parts of West Africa.
Lassa Fever has a 10% fatality rate, and the reservoir is the brown rat ( Mastomys natalensis).

Ebola

Ebola first emerged in southern Sudan and northeastern Zaire (now the Democratic Republic of Congo) in 1978.
Different strains cause the disease, and it is highly infectious and lethal (approximately 90% fatality rate).
In both Cameroon and Central African Republic, pygmies carry antibodies for the disease but there is no observed cases of the disease.
The source of the Ebola virus remains unknown.
Monkeys in the Philippines carry a third strain of the virus(Sudan strain of the virus is closer to Philippine strain).

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Description

Test your knowledge on the transmission, characteristics, and epidemiology of yellow fever. This quiz covers key aspects such as the virus's incubation period and the body's immune response to the infection. Perfect for students in microbiology or public health.