13 - Emerging Viruses Flashcards
What pathogen makes up the majority of emerging diseases?
Viruses, particularly RNA viruses due to their error prone RNA polymerase.
What factors contribute to emergence of new viral disease? Describe each.
- Demographics (increased pop density, trade, travel)
- Increased travel
- Changes in social behavior (unsafe sex, IVDU, increased antibiotic/antiviral use)
- Changes in environment (climate change, pop movement to new areas)
- Changes in industry/tech(new healthcare procedures, changes in food handling, identification methods)
- Changes in microorganisms (mutation)
What are some relatively recent emerging viruses?
- Hantaviruses
- Arboviruses - west nile, dengue, and zika
- Filovirus - Ebola
- Poxvirus - mokeypox
- Retrovirus - HIV
What are symptoms of Hantavirus? What is the host and how is it transmitted?
Acute onset pulmonary edema, shock, death (within days)
Host is the dear mouse, transmitted to humans by close contact or aerosolized virus
What disease is caused by hantavirus? Why did this virus emerge? How is it treated and what is the fatality rate?
Hantavirus-induced pulmonary syndrome
Emerged due to increased contact with mice due to 1. high rainfall, 2. plentiful food 3. increase mouse pop
No therapy, reduct contact with rodents. Fatality is 30-50%.
What are arboviruses and what type of disease do they cause?
Arthropod-borne (Arbo) viruses cause three general types of disease:
- Fever with or without maculopapular rash
- Encephalitis
- Hemorrhagic fever
Name the arboviruses? What family do they belong to?
West Nile, Dengue fever, and Zika.
All members of the flavivirus family.
What are symptoms of each arbovirus?
West Nile: causes milf fever or serious encephalitis
Dengue: causes fever or more serous hemorrhagic fever and dengue shock syndrome
Zika: causes milld dengue-like fever, but most common concern is microcephaly in infants and guillain-barre un adults
What caused the emergence of arboviruses?
- Increased range of vector (dengue and zika)
2. Introduction of virus vector/reservoir into a new area (west nile, zika)
When is west nile more likely to be contracted? What has preceded west nile spread in humans?
Late summer months.
Death of birds (particularly crows and bluejays) has, in the past, preceded human death from west nile virus.
What is the transmission and maintenance or arboviral encephalitis?
Birds are virus reservoir, and arthropod transmits from bird to bird.
Horse or human can be bitten by the arthropod (and become dead-end hosts).
Viremia is low in humans and horses so it’s not spread human-human (for west nile and st. louis encephalitis, can for dengue)
What are clnical features of west nile fever and severe disease caused by west nile virus? How often does each occur?
West nile fever (>80%): Fever Headache Swollen lymph glands Headache Skin rash on trunk Eye pain
Severe disease (<1%): meningitis and encephalitis
How do you diagnose west nile virus? Who should you consider might have it? How can we prevent it?
Relies on high index of clinical suspicion on results of specific lab tests.
Consider in adults >50 with unexplained encephalitis or meningitis in late summer/fall. Local dead birds.
Vaccine for horses not humans yet.
How is dengue virus transmitted? How many serotypes are there?
Mosquito vector or monkey.
4 serotypes: immunity to one does not mean immunity to the rest
What does the first infection with dengue fever result in? What occurs after infection?
“breakbone fever”
Fever, muscle/bone pain, joint pain, lymphadenopathy.
Nonfatal, then you have protection against re-infection with the same virus.
What occurs upon a second infection with dengue virus?
Dengue hemorrhagic fever and dengue shock syndrome.
When individuals with antibodies against one serotype are infected with another serotype.
Non-neutralizing Ab thought to increase infection of macrophages and cause release of inflamm cytokines.
What clinical symptoms occur as a result of a second dengue infection? What is the mortality rate?
Infected monocytes release vasoactive mediated and increase vascular permeability causing hemorrhage, rupture of vasculature, internal bleeding, plasma loss, and shock.
Mortality: 10-40%
What are two ways to diagnose dengue hemorrhagic fever?
Positive tourniquet test: tying a tourniquet will cause rupture capillaries resulting in petechiae
Virus antigen detection with immunofluorescnce
Elisa to detect antibodies: tells you which type of dengue the pt has
Why is dengue spreading? What is the key to prevention of dengue?
Due to re-emergence of the vector mosquito (aedes aegypti).
Vector control is the key to prevention.
How is zika virus transmitted? What is thought to be the reservoir? How did it emerge?
Day-time active mosquitoes, mother to fetus or during birth, sexual contact, and blood transfusions.
Monkeys thought to be the reservoir
Emerged by vector exposure/expansion, and travel
What are the clinical symptoms associated with zika virus?
Zika virus fever: fever, rash, joint pain, conjunctivitis; lasts a few days to a week.
Microcephaly in newborns with long-term consequences.
High associated with guillan-barre in adults.
What is the risk associated with pregnant women getting Zika? How do we prevent it?
Fetus is at risk at all stages of development for zika virus congenital syndrome.
Virus can infect and kill brain cells and can be found in fetal brains.
Best we can do currently is avoid exposure.
How is ebola virus transmitted? What is the reservoir?
Spillover event from animal to human; spread through direct contact with infected body fluids.
NOT spread by air, water, or insects.
Natural reservoir uncertain but is thought to be bats, which transmit to primates and humans.
When does ebola occur after exposure? what are the clinical symptoms?
Appears 2-21 days after exposure, avg of 8 days.
Initially, non-specific such as fever, headache, fatigue.
Diarrhea, vomiting, hemorrhage.
