Vector-Borne Viruses (Barr)

Key Takeaways

Arbovirus Diagnostic Framework

• Geography

  • Each virus maps to its vector’s range- learn the map

• Season

  • temp arboviruses peak summer-fall; tropical arboviruses are year round

• Vector

  • mosquito genus matters → predicts biting time, breeding habitat

• Exposure

  • outdoor activity, travel, roden contact - ask every time

No other diagnostic tool is more powerful for these pathogens

Alphavirus Encephalitis

• Severity: EEE → WEE → VEE

• EEE has 30-70% mortality

  • most severe US arbovirus

Chikungunya (Arthritis Alphavirus)

• Acute: abrupt high fever then severe symmetric polyarthralgia

• Chronic arthralgia: 30-40% of pts have joint pain for months-years

• Treatment is supportive only; no antivirals

  • NSAIDs/Acetaminophen for joint pain and fever

• Vector: Aedes aegypti & Aedes albopictus

  • daytime mosquito exposure (day-biters)

What are the 4 Flaviviruses

• Dengue

• Yellow Fever

• West Nile Virus

• Zika Virus

Dengue

• Antibody-Dependent Enhancement (ADE) → results in DHF or Dengue shock syndrome (DSS)

• Supportive care- fluid management, avoid NSAIDs and Aspirin

• Dengvaxia (vaccine) only for previously infected

  • no approved antivirals

Yellow Fever

• Vaccine

  • Live attenuated

  • Highly effective

  • Immunity likely lifelong

West Nile

• Infection causes flaccid paralysis

  • Anterior horn cell infection → asymmetric often permanent

• >50 yo are at risk for severe disease

Zika

• Congenital Zika Syndrome → microcephaly, brain calcifications, severe developmental delay

• Transmitted sexually

• Pregnancy Counseling critical

  • Avoid travel to endemic areas; if exposed, fetal ultrasound monitoring

La Crosse Encephalitis

• Most common arboviral in US children

• Seizures in 50-60%

• DEET repellents- apply to children before outdoor play (daytime exposure matters)

Rift Valley Fever (RVF)

• Vaccinate livestock prevents human cases (One Health)

  • One Health: collaborative, multisectoral approach recognizing that human health, animal health, and environmental health are interconnected

Crimean-Congo Hemorrhagic Fever (CCHF)

• Vector: Hyalomma tick

• Nosocomial (hospital acquired) Risk: Spreads to health care workers via blood/secretions

  • isolate pt as soon as suspected

  • full PPE required (gloves, gown, etc.)

• Treatment: Supportive + Ribavirin (start early)

  • limited evidence of ribavirin

Which rodent borne hemorrhagic fever is primarily cytolytic

a. HPS

b. HFRS

c. Lassa Fever

b

HPS

• Immune response causes the disease

• The virus is not replicating when pt crashes

  • antivirals at this point are irrelevant

• ~40% mortality

Lassa Fever

• Immune response causes the disease

• Ribavirin reduces mortality if given early

• Aerosol contact (human to human)

• Contact precautions required; BSL-4

Ribavirin

• Reduces mortality if given early in Lassa fever

• Considered in CCHF

• Considered in severe HFRS

• Useless for HPS

Pharmacist Prevention Role

• N95 counseling

  • mention hantavirus risk for rodent-infested spaces; reinforce wet-before-clean protocol

• DEET and permethrin

• Yellow Fever vaccine for travelers

• Zika pregnancy