Author:
Morgan P.Eutermoser
Description
- Vector-borne diseases account 17% of infectious diseases. Mosquitos are best known vector
- Severity of illness: Asymptomatic to fatal
- Despite control efforts, mosquito-borne illnesses are increasing. Climate change, animal migration patterns, travel and international trade contribute
- Several diseases are of particular importance in addition to malaria
- Dengue: 390 million dengue infections/yr; ¼ result in clinical illness. Endemic in more than 100 countries. 2nd most common cause of fever in returning travelers. 3.2 million cases in 2015 (WHO); substantial underreporting. Continuum of disease ranges from mild illness (Dengue fever [DF]) to severe findings (Dengue hemorrhagic fever [DHF] and Dengue shock syndrome [DSS]).
- Chikungunya: First reported in Americas (Caribbean) in 2013
- Zika: Significant concern in pregnant women (severe neurologic defects in developing fetus, esp. microcephaly). Between 2015-2018, 5,635 symptomatic cases reported in the U.S. (95% of cases were in travelers)
- West Nile Virus (WNV): Wild birds are main reservoir. Introduced in the U.S. in 1999. An outbreak in 2011 had a mortality rate of 4-5%. Cases were reported in 48 states
Etiology
- Mosquito-borne viruses are spread by 1 of 3 species of mosquitos: Anopheles (Malaria), Aedes (Dengue, Chikungunya, Zika), and Culex (WNV)
- Anopheles sp.
- Night biter
- Only transmits Malaria
- Aedes sp:
- Day biter
- Ae aegypti is the main vector; Ae albopictus is also able to spread disease. Breed in stand ing water (tires, garbage containers, buckets, vases)
- Transmits:
- Dengue: Tropical, subtropical regions: Asia, Africa, Central and South America, Caribbean. 4 serotypes of the virus: DEN-1, DEN-2, DEN-3, DEN-4. Subsequent infection by other serotypes increases risk of severe disease
- Chikungunya: Located in same regions as Dengue
- Zika: Pacific Island s and South America have the heaviest burden of infection. In North America, Mexico has the highest numbers of cases; however, Florida (2014) and Texas (2015) have reported cases
- Culex sp.:
- Night biter
- Transmits
- WNV: First discovered in 1937 in Ugand a. Secondary to bird migratory patterns, Endemic in Europe, India, Africa, Asia, Middle East, Australia, and North America. Horse and bird (crows) illness predictive of human risk
- Japanese encephalitis and lymphatic filariasis
- Other possible modes of transmission: Maternal fetal transmission, sexual contract, laboratory exposure, blood transfusion, breastfeeding
- WNV: Solid-organ transplant
- Breastfeeding is still recommended despite transmission risk due to benefits
Signs and Symptoms
- Overall, symptoms of an arbovirus infection consist of rash, fever, arthralgias. Nausea and vomiting are also common symptoms
- Dengue: Incubation period 4-10 d
- Dengue fever: Flu-like illness. Seldom causes death. High fever, headache, myalgias, retroorbital pain, lymphadenopathy, maculopapular rash that coalesces. After defervescence of fever, scattered petechial may develop. Rash coincides with fever in 50% of patients. Symptoms last 2-7 d
- Dengue hemorrhagic fever: Three phases of illness. 1: Febrile phase: similar to DF symptoms. 2: Critical phase: as fever declines, abdominal pain and vomiting ensue. This should be a warning sign to caregivers. This phase lasts 24-48 hr and is also known as the “leaky period” owing to the ascites, pleural effusions, petechial rash, epistaxis, overall bleeding tendency that occurs due to capillary leak and thrombocytopenia. This can either progress to circulatory collapse and death (DSS) or progress to the 3rd recovery phase
- Key physical exam findings and history: Patient returning from endemic area with coalesced rash, fever, arthralgias. If hand is placed on patient, the rash will blanch, leaving behind “slapped” appearance
- Chikungunya: Incubation period 3-7 d
- Most common symptoms are fever, arthralgia, joint swelling (bilateral), rash
- Most people will recover from initial illness within 1 wk; however, some may have joint pains persisting for weeks or months
- Severe disease in newborns (vertical transmission), adults ≥65, and people with comorbidities (hypertension, DM)
- Zika: Incubation period 3-14 d
- Symptoms in 18% of infected patients
- If symptomatic, mild sx of fever, rash, headache, arthralgias, and conjunctivitis for approximately 1 wk
- Most pronounced effect of virus is on the developing fetus
- Viremia x 1 wk. May be in semen
- Guillain-Barre syndrome
- WNV: Incubation period: 2-14 d
- Variable severity of illness:
- 80% asymptomatic
- 20% mild, flu-like illness
- 1/150 with CNS involvement
- Severity of illness is related to CNS involvement
- Risk increased in those over 50 yr and immunocompromised
History
- Diagnosis is based on clinical diagnosis and history more than lab findings
- Lives in endemic areas or travel history
- Zika: Travel to endemic area or unprotected sex with infected person
Physical Exam
Symptomatic patients present with the typical triad of rash (maculopapular), fever, and arthralgia
- Dengue:
- Rash prominent, especially in severe disease. Notable for coalescence of macular rash and petechial. In severe disease (DHF and DSS), narrowed pulse pressure, tachycardia, hypotension may be seen
- Easy bleeding
- Chikungunya:
- Similar findings to Dengue, but no hemorrhagic findings
- Chronic, longer lasting arthralgias
- Zika:
- WNV:
- Neurologic findings such as altered mental status, hyperreflexia, ataxia, CN palsies, paralysis, seizures, motor weakness, and meningismus. Long-term cognitive problems reported
Essential Workup
- Contact the Centers for Disease Control and Prevention for questions (970-221-6400)
- Procedures for submitting samples vary by state. Refer to public health guidelines
Diagnostic Tests & Interpretation
Lab
First week: RT-PCR, culture. End of first week: IgM, IgG. Trioplex RT-PCR (screens for Dengue, Chikungunya, or Zika).
- Dengue: Thrombocytopenia, neutropenia, elevated hematocrit (leaky plasma), ARF, hyponatremia, prolonged INR, PTT, PT, elevated dimer, low fibrinogen
- Chikungunya: No specific findings
- Zika: Testing recommended in pregnant woman without symptoms if a patient has exposure to Zika or if ultrasound abnormal
- WNV: CSF - lymphocytic predominance, elevated protein, normal glucose. The most sensitive screening test for WNV is IgM testing of both CSF and serum. Other lab abnormalities: leukocytosis (50%), leukopenia (15%), hyponatremia
Imaging
Indicated for specific diseases to treat symptoms but is not helpful in diagnosing specific virus.
- Dengue: CXR may show pleural effusions. Consider CT head if change in mental status or trauma (bleeding risk). Abdominal ultrasound can show ascites
- Chikungunya: No definite imaging indicated
- Zika: If pregnant, multiple ultrasounds may be necessary to follow fetal progression
- WNV: CT head usually normal. MRI can show CNS inflammation with enhancement of leptomeninges and /or periventricular white matter or can mimic demyelinating process
Diagnostic Procedures/Surgery
- Dengue: Tourniquet Test: Inflate BP cuff to median BP. Test is positive if 3 or more petechiae appear per cm²
- Chikungunya: None
- Zika: None
- WNV: Lumbar puncture
Differential Diagnosis
- Infection
- Viral Illness: Nonspecific, influenza, rubella, rubeola, mononucleosis, roseola infantum
- Rocky Mountain spotted fever
- Malaria
- Leptospirosis
- Gastroenteritis
- Secondary syphilis
- HIV
- Typhoid
- Toxic shock syndrome
- Appendicitis
- Encephalitis (HSV, CMV, EBV, VZV, enterovirus, other arboviruses)
- Kawasaki disease
- Still disease
Initial Stabilization/Therapy
- ABCs
- If sick, IV access, monitor, IV fluids, O2
- Seizure precautions if concern for WNV
ED Treatment/Procedures
- Dengue: TREATMENT is supportive for DF, DHS, DSS. IV FLUIDS for hypotension and dehydration. Acetaminophen for fever. No aspirin or NSAIDS due to dysfunctional platelets. Platelet transfusion controversial for thrombocytopenia. If diagnosed early with appropriate treatment, mortality rate decreases from 20% to <1%.
- Chikungunya: Supportive. Acetaminophen only for fever until dengue ruled out
- Zika: Supportive. Acetaminophen only for fever until dengue ruled out
- WNV: Supportive care. For signs of meningitis, administer antibiotics/antivirals pending results of CSF. Antipyretics. No known effective antiviral therapy or Lancet vaccine. No controlled studies proving efficacy of interferon α-2b, ribavirin, corticosteroids, anticonvulsants, or osmotic agents
Disposition
Admission Criteria
- Dengue: Consider admission for signs of DHS or DSS (hypotension, DIC, thrombocytopenia, hemoconcentration) or poor follow-up
- Chikungunya: Severe pain requiring IV medications, dehydration
- Zika: No admitting criteria typically, unless concern for Guillain-Barre syndrome
- WNV: Neurologic symptoms, dehydration, concerning risk factors (advanced age, immunocompromised)
Discharge Criteria
- Dengue: Minimal well-defined illness, close follow-up, pain controlled and tolerating po
- Chikungunya: Pain controlled, tolerating po
- Zika: No neurologic signs
- WNV: No signs of CNS involvement
Follow-up Recommendations
- Close follow-up for patients presenting with signs of Dengue to monitor for worsening disease
- Women in endemic areas, traveling to endemic area, or involved in sexual contact with infected men or men from endemic areas should be counseled on Zika risk. If exposure exists, close obstetrical and ultrasound monitoring
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