169: Mosquito-borne Diseases Flashcards
(66 cards)
What are the common characteristics of Flavivirus infections?
Most common mosquito-borne infections worldwide. Febrile illness associated with rash, conjunctivitis, or both. Complications may include hemorrhagic or neurologic disease. Zika virus can be transmitted from mother to child and through human secretions.
What are the two categories of Alphavirus and their associated diseases?
What is the primary site of infection for Flavivirus and which viruses demonstrate skin tropism?
The primary site of infection for Flavivirus is the skin. The viruses that demonstrate skin tropism with cutaneous manifestations include: Dengue virus, Zika virus, West Nile virus, Yellow Fever virus, Spondweni virus.
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Flavivirus infections are primarily associated with febrile illness with rash, conjunctivitis, or both. Potential complications include hemorrhagic or neurologic disease. The Zika virus can also be transmitted from mother to child and through human secretions.
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| Old World | Associated with dermatologic and rheumatic diseases in humans | Chikungunya virus, Mayaro virus |
| New World | Associated with fatal encephalitic disease in Americas | Venezuelan, Eastern, Western, and Venezuelan Equine Encephalitis |
Type | Clinical Manifestations | Examples |
What is the role of the first line of defense against Flavivirus infections, and which cells are involved?
The first line of defense against Flavivirus infections is crucial for preventing viral entry and spread. The involved cells include: Epidermal Langerhans cells, Dermal dendritic cells, Macrophages, T cells.
What are the clinical manifestations of Dengue Virus (DENV 1-4)?
- 70% asymptomatic
- 10-15% self-limited febrile illness (40°C), severe headache, retro-orbital pain, malaise, severe joint and muscle pain, nausea, and vomiting
- 50-80% maculopapular or urticarial exanthem in febrile phase
- 3-4 days after fever onset, 70% experience ‘Islands of White in a Sea of Red’ (generalized morbiliform dark erythematous eruption with areas of clearing, involves palms and soles, with desquamation)
- Critical phase occurs around defervescence
- 15-30% may have oral or genital bleeding, indicating dengue hemorrhagic fever.
What laboratory tests are used for confirming Dengue Virus infection?
- Dengue RT PCR: preferred method of virologic confirmation, (+) in 69-82% in first 3 days of illness
- Dengue NS1 Antigen: parallels viremia, (+) in 84-90% in first 5-7 days of illness
- Dengue IgM: (+) in 10-20% after 5 days of illness, (+) in 80-90% after 10 days of illness
- Leukopenia, thrombocytopenia (<100,000), elevated transaminases, elevated hematocrit, hyponatremia.
What are the potential complications of severe Dengue Virus infection?
- Metabolic acidosis
- Hypovolemic shock
- Organ failure
- Disseminated intravascular coagulation
- Severe dengue can also lead to: 1. Hepatitis 2. Neurologic disorders 3. Myocarditis
- Mortality rate can be as high as 20%.
What is the recommended treatment for Dengue Virus infection?
- Rehydration and Supportive care
- Avoid NSAIDs!
- Live attenuated recombinant vaccine with 4 dengue serotypes has been shown to decrease: 1. Severe dengue by 90% 2. Hospitalization by 80% 3. Clinical dengue by 50-60%.
A patient presents with a high fever, severe headache, retro-orbital pain, and a maculopapular rash. They recently traveled to a dengue-endemic area. What diagnostic tests would you prioritize and why?
Dengue RT-PCR is the preferred method of virologic confirmation, especially in the first 3 days of illness. Dengue NS1 Antigen is also useful in the first 5-7 days. IgM serology becomes positive after 5 days of illness.
A patient presents with a febrile illness and a rash described as ‘Islands of White in a Sea of Red.’ What is the likely diagnosis and the associated vector?
The likely diagnosis is Dengue Fever, and the associated vector is Aedes mosquitoes.
A patient presents with fever, severe headache, and retro-orbital pain. What mosquito-borne viral disease should be suspected, and what is the critical phase of this disease?
Dengue Fever should be suspected. The critical phase occurs around defervescence and may involve plasma leakage and bleeding.
What are the clinical manifestations of Dengue Virus (DENV 1-4) during the critical phase?
During the critical phase of Dengue Virus (DENV 1-4), the clinical manifestations may include:
1. Oral or genital bleeding (15-30%) signaling dengue hemorrhagic fever.
2. Acute gingival and palate bleeding.
3. Dryness of the mouth.
4. Taste changes.
5. Erythematous plaques and vesicles on the tongue and palate.
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The preferred laboratory tests for confirming Dengue Virus infection include: 1. Dengue RT PCR: Preferred method of virologic confirmation; positive in 69-82% of cases within the first 3 days of illness. 2. Dengue NS1 Antigen: Parallels viremia; positive in 84-90% of cases within the first 5-7 days of illness. 3. Dengue IgM: Positive in 10-20% after 5 days and in 80-90% after 10 days of illness. 4. Leukopenia and Thrombocytopenia: Leukocyte count <100,000, elevated transaminases, elevated hematocrit, and hyponatremia are also indicative of infection.
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Potential complications of severe dengue include:
1. Metabolic acidosis: Can lead to organ dysfunction.
2. Hypovolemic shock: May require immediate medical intervention. 3. Organ failure: Increases morbidity and mortality rates. 4. Disseminated intravascular coagulation: Can complicate the clinical picture significantly. 5. Neurologic disorders: May arise as a result of severe infection. 6. Myocarditis: Can affect cardiac function. The mortality rate can be as high as 20%, particularly in infants due to maternal antibodies.
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Preventive measures against Dengue Virus include: 1. Avoiding NSAIDs: To reduce the risk of bleeding complications. 2. Vector control: Reducing Aedes mosquito populations through environmental management and personal protection measures. 3. Vaccination: A live attenuated recombinant vaccine with 4 dengue serotypes has shown to decrease: - Severe dengue by 90% - Hospitalization by 80% - Clinical dengue by 50-60%. Vaccination is significant as it provides a proactive approach to reducing the incidence and severity of dengue infections, especially in endemic areas.
What are the main clinical features of Zika virus infection?
- 80% asymptomatic
- 70-85% micropapular rash, mainly on trunk and extremities
- Very pruritic, often leading to consultation
- 60% nonpurulent conjunctivitis
- 50% acral edema in adults (15% in children)
- Leukocytosis, thrombocytopenia, elevated transaminases.
What is Congenital Zika syndrome and how is it diagnosed?
Congenital Zika syndrome is characterized by:
1. Microcephaly
2. Chorioretinitis
3. Hearing loss
4. Irritability
5. Hypertonia
6. Esophageal dysfunction
Diagnosis includes:
1. Head ultrasonography
2. MRI
3. Hearing examination
4. Ophthalmologic examination.
What are the key features of Yellow fever virus infection during the acute phase?
- Facial flushing
- Conjunctival hyperemia
- Symptoms improve in 3-4 days
- Toxic phase (15% of cases) includes:
1. Jaundice (hallmark of infection)
2. High fever
3. Petechiae
4. GI hemorrhage
5. Renal Failure
6. Shock
What is the recommended treatment for Yellow fever virus infection?
- No approved antiviral treatment
- Treatment includes Nitazoxanide to prevent replication
- Vaccine (1 dose) confers lifelong immunity.
A pregnant woman presents with a history of a very pruritic micropapular descending rash with facual, neck and acral edema and nonpurulent conjunctivitis. What specific diagnostic tests and imaging would you recommend to assess the fetus?
Suspect Zika virus infection. Head ultrasonography, MRI, hearing examination, and ophthalmologic examination are recommended to assess for congenital Zika syndrome.
A patient presents with jaundice, high fever, and petechiae after returning from a trip to South America. What is the likely diagnosis and the hallmark pathophysiological feature?
The likely diagnosis is Yellow Fever. The hallmark feature is hepatocellular necrosis with the formation of intracellular hyaline deposits in hepatic lobules.
A patient presents with Guillain-Barré syndrome 4 weeks after a febrile illness. What mosquito-borne viral infection should be considered, and what is the underlying mechanism?
Consider Zika virus infection. The underlying mechanism is a post-infectious host-directed immune response.
