Emerging Viruses Flashcards
What percentage of human morbidity and mortality derive from infectious disease?
25%
Factors contributing to the emergence of new virus disease
- Increased population and population density
- Increased travel
- Changes in social behavior
- Changes in environment
- Changes in industry/technology
- Changes in microorganisms (mutation)
Changes in demographics - Population growth
World population reached 6 billion on Oct 11, 2000
300 million in US on Oct 17, 2006
Production and distribution of _____ ______ broadened the distribution of HIV/AIDS
blood products
____ and ____ are clear examples where travel was an important facilitator of disease spread
SARS; HIV
Changes in behavior
- Promiscuous sex
- Intravenous drug use
- Increased antibiotic/antiviral use
- Increased use of day care
Changes in the environment
Climate change
Population movement into new territories
Habitat destruction
Changes in the virus
- Mutation of surface molecules
- Mutation to antigenic difference so prior immunity is no longer effective
- Mutation to make it more pathogenic
- Mutation to antiviral resistance
- Change due to reassortment of segmented genomes
Hantavirus - characterized by:
Fever Hemorrhage 5-10% mortality Headache Acute renal failure
Hantavirus in four corners area of US
Disease:
Emergence:
Host:
Disease: Pulmonary syndrome, pulmonary edema, shock, death
Emergence: due to High rainfall; plentiful food, increased mouse population
Host: deer mouse
Number of cases of Hantavirus pulmonary syndrome
2012 cases:
Fatality rate:
Last noted outbreak:
2012 cases: 29
Fatality rate: 30-50%
Last noted outbreak: Yosemite Park
Arbovirus (Arthropod Borne) cause three general types of disease…
Fever + maculopapular rash
Encephalitis
Hemorrhagic fever
West Nile and Dengue (Arboviruses) characteristics
- Flaviviruses
- Enveloped ss (+)RNA, replicate similar to other such viruses
- West Nile causes mild ‘fever’ or serious encephalitis
- Dengue causes ‘fever’ or more serious hemorrhagic fever and dengue shock syndrome
Emergence of Arboviruses:
Due to increased range of vector (dengue) or introduction of virus reservoir (bird, human, mosquito) into a new area
Describe the origin of West Nile Virus starting in the Bronx Zoo…
In 1999, unusual deaths of exotic birds in Bronx Zoo
Crows/jays in NYC area
Birds and Culex Pipiens mosquitoes tested positive
Not long after, human cases noted
Which year was the worst year in terms of West Nile Cases?
2003: 9862 cases; 264 fatalities
Why did West Nile Virus increase in the US in 2012?
Unknown Possibly weather (mild winter and hot summer) Less water so more bird/bug interaction
Transmission and Maintenance of Arboviral encephalitis
Virus reservoir in birds (in US, crows and Jays most affected by WNV)
Arthropod serves as vector to transmit from bird to bird
Horse or human - usually dead end hosts, viremia low and not transmitted back to vector
Clinical features of West Nile Fever:
Severe Disease:
Clinical features of West Nile Fever: fever, fatigue, swollen lymph glands, headache, rash, eye pain
Severe Disease: Meningitis, Encephalitis, GI symptoms, Seizures, Change in mental status
Diagnosis of WNV infection
High index of clinical suspicion and results of lab tests
- Consider in adults > 50 years of age or older with unexplained encephalitis or meningitis in late summer/fall
- Local WNV activity in area (dead birds)
- Vaccine available for horses
- Vaccine for humans in development
Dengue virus - Hemorrhagic Fever
Dengue (a Flavivirus)
- 4 serotypes
- Mosquito transmission from human or monkey
- Causes dengue fever or “breakbone fever” - muscle/bone pain, joint pain, lymphadenopathy
Dengue hemorrhagic fever and Dengue shock syndrome
- Occurs when individual antibodies against one serotype is infected with another serotype
- Non-neutralizing Ab thought to increase infection of Macs, release of inflammatory cytokines
- Causes rupture of vasculature, internal bleeding, plasma loss, and shock
- DHF/DSS on rise due to import of serotypes in new areas
Why are non-neutralizing antibodies to a first infection with Dengue virus harmful upon second infection
Cause inappropriate immune response to virus
Infected monocytes release vasoactive mediators and increase vascular permeability - hemorrhage
Diagnosis of Dengue hemorrhagic fever
Positive tourniquet test (>20 petechiae/inch^2)
Virus antigen detection
- ELISA to detect antibodies
- Tetravalent vaccine being developed
Dengue is spreading due to re-emergence of the ______ _______
vector mosquito
Key to Dengue virus prevention
Vector control
Monkeypox
- Relatively rare disease occurring mostly in Africa
- Monkeypox was first isolated in 1958 in lab monkeys - later shown in African squirrel
- Virus a member of Poxvirus family
- First human case in 1970 (not generally fatal)
Path of transmission of Monkeypox (animals)
African squirrel → African Rats → Prairie Dogs → Transmission to pet owners
Path of transmission of Monkeypox (states)
Texas → Iowa → Illinois → Wisconsin
Monkeypox Incubation time: Symptoms: Vaccine: Reason for emergence:
Incubation time: about 12 days
Symptoms: fever, headache, muscle aches, backache
Vaccine: smallpox vaccine (shares antigenicity)
Reason for emergence: Change in behavior (pet choice) and movement of virus (and reservoir) into new areas as a result of commerce
HIV emergence Environment: Population: Lifestyle changes: Poverty: Travel: Sex trade: Technology:
Environment: transfer of HIV from chimp to human
Population: often spurred by war
Lifestyle changes: Loss of traditional cultures, more sex partners
Poverty: Commercial sex trade
Travel: The flight attendant who had 100s of sex partners
Sex trade: in Asia - exported exposures to other Countries
Technology: Infected blood products from US
