Yellow Fever Virus

What causes Yellow Fever?

Yellow fever virus

What is the yellow fever virus?

A positive single strand RNA virus of the family Flaviviridae

Basic info about Yellow fever

• belongs to the group of hemorrhagic fevers

• infects monocytes, macrophages, Schwann cells, and dendritic cells

Vectors of Yellow Fever Virus (YFV)

1. Aedes spp.

2. Haemagogus spp.

3. Sabetes spp.

Aedes spp. as a YFV vector

Aedes aegypti; Aedes africanus, semi domestic Aedes app.

• Urban Yellow fever cycle

• Jungle and Savanna cycles

Haemagogus spp. as a YFV vector

• Central and South America

• Canopy forest

• Jungle or sylvatic yellow fever cycle

Sabetes spp. as a YFV vector

• Central and South America

• Forest mosquitoes

• Jungle or sylvatic yellow fever cycle

Who are the hosts of Yellow fever virus?

Humans and non-human primates

Yellow Fever Transmission Cycle in South America

• In urban cycles, humans are the hosts

• No non-human primates contribute to the epidemics of yellow fever

• Humans and mosquitoes are drivers for the disease

Yellow Fever Transmission Cycle in Africa

• Transmission mainly contributed by humans

• Humans contribute to the spill-over; Spill-over of yellow fever in jungle can start cases in the urban cycle

• Includes an intermediate cycle

What is the intermediate cycle in the YF transmission cycle in Africa?

• A mixed cycle where Aedes bites primates (humans and non-humans alike)

• Intermediate cycles put them into close contact

• Behavior of mosquitoes can contribute to the cycles

Clinical Signs and Symptoms of Yellow Fever

• Most people with YFV have no symptoms or mild symptoms and typically recover

• Most people who develop symptoms improve in one week

• For those who recover develop weakness and fatigue that might last several months

• Once you get infected, you are likely protected from future infections

Severe Form of Yellow fever

• A few people develop a more severe form of the disease (15%)

• Severe symptoms: high fever, yellow skins or eyes (jaundice), bleeding, shock, and organ failure

Diagnosis for Yellow Fever

• a presumptive diagnosis is based on patient's clinical features, places, and dates of travel, activities, and epidemiologic history of the location where the presumed infection occurred

Treatment and Vaccine for Yellow Fever

• There is no medicine to treat yellow fever

• There is a vaccine to prevent the disease

• Avoid nonsteroidal anti-inflammatory drugs

• Go to the hospital for close observation and supportive care if severe yellow fever develops

Epidemiology of Yellow Fever

• transmitted to people primarily through the bite of infected Aedes mosquitoes

• people infected with yellow fever virus are infectious to mosquitoes shortly before the onset of fever and up to 5 days after onset

Who is at risk for yellow fever virus?

Anyone exposed to mosquitoes in countries where yellow fever is endemic is at risk, including travelers, unless they have received the yellow fever vaccine

Impact of one dose of yellow fever vaccine

a single dose of YFV vaccine provides lifelong protection for most people

Are there any treatments for patients with yellow fever?

No, there are no specific treatments are found to benefit patients with yellow fever

How to prevent spread of Yellow fever to uninfected mosquitoes?

• protect yourself from mosquito bites up to 5 days after symptoms begin