Yellow Fever | Pathogenesis (mosquitoes, virus), Signs & Symptoms, Diagnosis and Treatment

Summary

This lesson on yellow fever covers its causes, pathogenesis, symptoms, diagnosis, and management. Yellow fever, a hemorrhagic fever caused by Flavivirus, is transmitted by mosquitoes, particularly Aedes aegypti and Haemagogus species. The infection progresses through three stages: initial fever and malaise, a potential remission, and severe intoxication with organ dysfunction and hemorrhagic symptoms. Diagnosis relies on serological tests and PCR, while treatment focuses on supportive care, as no specific antiviral therapy exists. Vaccination with the yellow fever 17D vaccine is crucial for prevention, particularly for those traveling to endemic areas.

Takeaways

• 🦟 Yellow fever is a hemorrhagic fever caused by viruses from the Flavivirus family, primarily transmitted by mosquitoes.
• 🌍 Endemic areas for yellow fever include sub-Saharan Africa and South America, where specific mosquito species are prevalent.
• 🐒 The virus can be transmitted from infected monkeys to humans or from person to person through mosquito bites.
• 💉 Older adults have a worse prognosis if infected with yellow fever, highlighting the importance of prevention.
• 🔬 Infection begins when a mosquito inoculates the virus, leading to local replication in dendritic cells and lymph nodes.
• 🩸 The three stages of yellow fever infection are: period of infection, period of remission, and period of intoxication.
• 🤒 Symptoms during the period of infection include fever, malaise, headache, and conjunctival redness.
• ⚠️ The period of intoxication may lead to jaundice, organ dysfunction, and severe hemorrhagic symptoms.
• 🧪 Diagnosis typically involves serology (ELISA), PCR for viral detection, or post-mortem histopathology.
• 💊 There is no specific antiviral treatment; management is supportive, emphasizing hydration and symptom control.

Q & A

What is yellow fever?

Yellow fever is a hemorrhagic fever caused by viruses from the Flaviviridae family, specifically transmitted by mosquitoes.

How is yellow fever transmitted?

Yellow fever is transmitted primarily through the bite of infected mosquitoes, particularly the Aedes aegypti in Africa and the Haemagogus species in South America.

What are the primary risk factors for yellow fever infection?

Risk factors include travel to endemic areas in sub-Saharan Africa and South America, and older age increases the severity of the prognosis.

What are the stages of yellow fever infection?

There are three stages: the period of infection, the period of remission, and the period of intoxication.

What symptoms occur during the period of infection?

Symptoms include fever, malaise, headache, myalgia, nausea, vomiting, and photophobia, along with a slow heart rate compared to the fever.

What happens during the period of remission?

During this stage, fever and symptoms may subside for at least 48 hours, but about 15% of patients may progress to the next stage.

What symptoms characterize the period of intoxication?

Symptoms include a return of fever, jaundice, oliguria, organ dysfunction, bleeding, and potential CNS effects such as agitation and convulsions.

How is yellow fever diagnosed?

Diagnosis involves serology tests like ELISA for IgM antibodies, PCR for viral genome detection, and postmortem histopathology.

Is there a specific treatment for yellow fever?

There is no specific antiviral treatment for yellow fever; management is primarily supportive, focusing on hydration and treating complications.

What is the most effective prevention method for yellow fever?

The best prevention method is vaccination with the live attenuated yellow fever 17D vaccine.