169: Mosquito-borne Diseases Flashcards
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.
delete
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.
delete
|————|———————————————————|———————————–|
| 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.
delete
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.
delete
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.
delete
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.
A patient presents with jaundice and gastrointestinal hemorrhage after traveling to South America. What mosquito-borne viral disease should be suspected, and what is the mortality rate for its toxic phase?
Yellow Fever should be suspected. The mortality rate for the toxic phase is 40-50%.
A patient presents with fever, conjunctivitis, and a descending rash involving the palms and soles. What mosquito-borne viral disease is most likely, and what is the primary diagnostic test?
The most likely disease is Zika virus infection. The primary diagnostic test is blood RT-PCR, which is diagnostic in the first 5-10 days.
A patient presents with fever, jaundice, and petechiae after traveling to Africa. What mosquito-borne viral disease should be suspected, and what is the hallmark clinical feature?
Yellow Fever should be suspected. The hallmark clinical feature is jaundice due to hepatocellular necrosis.
A patient presents with fever, rash, and conjunctivitis. They recently traveled to a Zika-endemic area. What is the primary mode of transmission for this virus?
The primary mode of transmission is through Aedes mosquitoes, but it can also be transmitted through body fluids, sexual contact, and vertically from mother to fetus.
Guillaine-Barre syndrome occurs how many weeks after a ZIKV infection?
2-6 weeks.
ZIKV persists for up to 6 months after illness in this bodily fluid.
Semen–longer than ni blood, saliva or urine.
T or F: Majority of those infected with the Yellow fever virus recover fully from acute phase with no consequences and lifelon immunity.
True.
In what situations will there be falsely positive tests to the Zika virus and how can this be resolved?
Dengue endemic areas. This is resolved with a plaque reduction neutralization test, which improved differentiation between flavivirus in endemic areas.
What is the pathogenesis of the Yellow fever virus?
It replicates within the endoplasmic reticulum of hepatocytes and other organs such as the kidneys, heart and GIT.
T or F: 1 dose of Yellow fever virus vaccine confers lifelong immunity.
True.
A patient returning from Africa presents with fever and jaundice. Two weeks ago, he reported to have facial flushing and conjunctival hyperemia. What is your diagnosis and its mortality rate?
Yellow fever virus. There is 40-50% mortality rate in those progressing to toxic phase.
What laboratory findings are indicative of Zika virus infection during the acute phase?
Laboratory findings include leukocytosis, thrombocytopenia, elevated transaminases, blood RT-PCR diagnostic in the first 5-10 days, and IgM positive in 5-15 days.
What is the recommended treatment for Yellow fever virus infection?
The recommended treatment includes supportive care for symptoms and nitazoxanide to prevent replication. There is no approved antiviral treatment.
What is the incubation period for West Nile Virus?
The incubation period is typically 3 to 14 days, up to 28 days.
What are the common presentations of West Nile Virus infection?
- asymptomatic (70%)
- high fever (20%)
- generalized fatigue (75%)
- headache (48%)
- nausea or vomiting (44%)
- back or limb pain (35%)
- roseola-like rash (20%)
What are the preventive measures against West Nile Virus?
Preventive measures include wearing long clothing and using insect repellents containing DEET, Picaridin, IR3535, or oil of lemon eucalyptus.
What is the test of choice for diagnosing neuroinvasive disease caused by West Nile Virus?
The test of choice is CSF IgM with confirmatory plaque reduction neutralization test.
What are the risk factors associated with severe outcomes from West Nile Virus?
Risk factors include old age, chronic medical conditions, and immunosuppression.
What is the mortality rate associated with West Nile Virus?
The mortality rate is approximately 9%.
What are the key diagnostic findings in cerebrospinal fluid (CSF) for neuroinvasive disease presenting with acute flaccid paralysis from West Nile Virus?
CSF findings include lymphocytic pleocytosis with less than 500 cells/mm³.
What is the most common long-term symptom of West Nile Virus infection?
The most common long-term symptom is fatigue, occurring in 95% of cases for up to 1 month.
The nonpruritic rash of West Nile virus characterized by small pink to red macules and papules on the torso and proximal extremities (roseola-like) spare what body areas and last for how many days?
Palms and soles. Lasts 5-7 days.
What are the clinical manifestations of Chikungunya virus (CHIKV)?
Clinical manifestations include high fever (>39C), headache, severe polyarthralgia, myalgia, and erythematous maculopapular rash.
What laboratory tests are recommended for diagnosing Chikungunya virus (CHIKV)?
Recommended tests include CBC (leucopenia, lymphopenia), viral culture, RT-PCR (preferable), and IgM/IgG serology (after 1 week of illness).
What are the key clinical features of Mayaro virus infection?
Key features include arthralgia and arthritis in 50-90% of cases, acute febrile illness in 45%, and rash in 30-50%.
What is the most common and feared complication associated with Chikungunya virus (CHIKV)?
The most common complication is chronic, episodic, often debilitating polyarthralgia or polyarthritis associated with fatigue.
What is the primary diagnostic test for Chikungunya virus?
The primary diagnostic test is RT-PCR.
What distinguishing feature of Mayaro virus should be considered when diagnosing?
A distinguishing feature is arthralgia accompanied by joint edema, causing temporary incapacity, persisting for 2 months with decreasing severity.
What are the common clinical manifestations of O’nyong-nyong virus infection?
Common manifestations include arthralgia and arthritis in 60-100%, acute febrile illness in 80-100%, and rash in ≤90%.
What are the clinical features of Ross River virus infection?
Clinical features include arthralgia and arthritis in 80-100%, acute febrile illness in 20-60%, and rash in 30-50%.
What are the key clinical manifestations of Sindbis virus infection?
- Arthralgia and arthritis in 90% (can last 6-12 months)
- Acute febrile illness in 15-40% with headache, malaise, myalgia
- Rash is almost universal (≤90%)
What are the mosquito vectors for DENV, ZIKV, YFV, WNV, and CHIKV?
- DENV: Aedes
- ZIKV: Aedes
- YFV: Aedes (South America), Haemagogus (Africa)
- WNV: Culex
- CHIKV: Aedes aegypti and albopictus
Most common presentation of rash in CHIKV infection?
Morbiliform.
A patient presents with fever, arthralgia, and a rash that persists for 2 months. They recently traveled to Uganda. What is the likely diagnosis, and what is the primary prevention strategy?
The likely diagnosis is O’nyong-nyong virus infection. The primary prevention strategy is wearing protective clothing and using insect repellents and insecticide-impregnated mosquito nets.
A patient presents with fever, headache, and a rash after traveling to Queensland, Australia. What mosquito-borne viral disease should be considered, and what is the incubation period?
Consider Ross River virus infection. The incubation period is 7-9 days.
A patient presents with fever, malaise, and a rash after traveling to Eurasia. What mosquito-borne viral disease should be considered, and what is the most common complication?
Consider Sindbis virus infection. The most common complication is arthralgia and arthritis, which can last 6-12 months.
Incubation period of DENV, ZIKV, YFV, WNV, CHIKV?
- DENV: 3-10 days
- ZIKV: 3-7 days
- YFV: 3-6 days
- WNV: 3-14 days (28 days or less)
- CHIKV: 2-6 days
Cranial nerve palsies can happen in this mosquito-borne viral disease.
West Nile virus infection.
T or F: RT-PCR is not helpful in an acute disease caused by WNV infection.
True. RT-PCR is positive in the 1st 3-5 days of illness but is usually negative upon presentation.
T or F: Flavivirus and Alphavirus are both ssRNA.
True.
This virus is maintained in enzoonotic cycle with births and mosquitoes.
West Nile virus.
CHIKV RNA persists in macrophages for how long?
90 days.
