Unit 3 - Poxviruses Flashcards
1
Q
What is the history of Poxviruses?
A
“Smallpox is the lion king of infectious diseases”
- Smallpox killed over 500 million people in the 20th century~
- Compare to 320 million deaths caused by wars, the spanish flu, and AIDS combinded.
- Smallpox left people scarred by pockmarks and sometimes blind from corneal ulcerations
- Famous victims and survivors of smallpox
- Life-mask of composer and pianist Beethoven
2
Q
What are some more things involved in the history of smallpox?
A
First evidence of smallpox
- Pustular rash on mummified remains of Egyptian Pharaoh Rames V
- Written descriptions: China and southwestern Asia
Smallpox carried by explorers and traders from the Old world to the New World where the population had no immunity to it
- Killed an estimated 400,000 Europeans per year during the late 18th century and was responsible for 1/3 of all blindness.
3
Q
What is the relationship between smallpox and the new world?
A
- 15th century: Pizarro and the Incas
- French and Indian War (1754-1763): Lord Jeffery Amherst provided Native Americans tainted blankets
4
Q
What are the clinical features of human poxviruses?
A
Smallpox is caused by two strains of the same virus:
- Variola Major: more common, causes a severe form of the disease; overall fatality rate of 30%
- Variola Minor: causes a mild form of disease; 1%-2% mortality rate
5
Q
What are the four types of Variola Major smallpox?
A
- Ordinary: accounts for > 89% of cases; 30% mortality rate
- Vaccine modified: mild, occured in 2.1% of previously vaccinated person, not lethal
- Flat or malignant pox: rare, very severe; lesions do not project above the skin surface; represents 6.7% of cases; 90% mortalilty rate
- Hemorrhagic: rare, very severe; hemorrhages develop in skin and mucous membranes; 2.4% of cases; 96% mortality rate
6
Q
What are ordinary smallpox?
A
Centrifugal maculopapular rash (less lesions on trunk, more on face and extremities)
7
Q
What are Hemorrhagic Smallpox?
A
The pictures
8
Q
What is variola Minor?
A
- Less common, mild disease, 1% or less mortality rate
- Last known person to have natural smallpox of any kind lived in Merka, somalia in 1977.
9
Q
What are the Clinical presentations of smallpox?
A
Average incubation period is 12–14 days.
- Infected individual is not contagious during the incubation period
First symptoms:
- Fever of 101o to 104oF
- Splitting headache
- Severe backache
- Vomiting (50% of individuals infected)
- Diarrhea (10% of individuals infected)
- Delirium and convulsions (7%–15% of individuals infected, usually children)
10
Q
What is involved during the prodromal Phase of Smallpox?
A
- 2–4 day period
- May be contagious during this phase
- Infected individuals too sick to carry on normal daily activities
- Fever declines, individual feels better (2nd or 3rd day)
- A macular rash appears around the mouth and on the palate/pharynx
- Spreads to face, proximal extremities, and finally palms/soles
- Rash then becomes papular (raised) and vesicular (blistery).
- Contains large numbers of virus particles
11
Q
What is involved in the progression of smallpox?
A
- As vesicles rupture, large numbers of virus particles are liberated into the saliva. Person is MOST contagious at this stage!
- Lesions line the respiratory tract.
Some infected individuals may experience a sore throat.
- When the vesicles in the mouth start to break, a skin rash appears: first on the face, spreading to the arms, legs, hands and feet within 24 hours.
Rash is described as being centrifugal.
Important in distinguishing smallpox from chickenpox
12
Q
The smallpox progression continued?
A
- Skin vesicles mature into pustules by the seventh day.
- The second week, the rash crusts over.
- Scabs fall off by days 22–27.
- In fatal cases, death occurs between days 10 and 16 of the illness.
- The infected individual remains contagious from the onset of the rash, until all of the scabs come off.
13
Q
What is monkeypox?
A
- Human infections are rare.
- Before 1970, recognized as a disease of animals in the rainforests of central and western Africa.
- Between 1970 and 1986, first human cases reported from Western Africa and Congo basin of Africa as smallpox disappeared.
- The smallpox vaccine protects individuals from contracting monkeypox.
- Recommended for those with close contact with individuals or animals confirmed to have monkeypox
14
Q
What else in involved in Monkey pox?
A
- 1996–1997 in 13 villages in Zaire: first human-to-human transmission of monkeypox
- Lack of smallpox vaccination and an epidemic in animals allowed the virus to jump the species barrier into humans
- June 2003, U.S. multistate monkeypox outbreak: exotic pet swap meet (prairie dogs)
- Case fatality rate is 1%–14%
- Signs and symptoms similar to ordinary or modified smallpox but milder
- Infected individuals experience a fever, vesicular rash.
- Monkeypox victims suffer from lymphadenopathy (enlarged lymph nodes) during the early stages of disease.
15
Q
What is Molluscum Contagiosum (MCV)?
A
- Common poxvirus infection; ~1% of all skin infections
- Transmitted by direct contact, including sexual contact or more commonly through indirect contact (fomites, e.g., sharing towels from swimming pools).
- Rapidly transmitted among children at daycares and kindergartens.
- Becoming a significant opportunistic infection of AIDS patients.
16
Q
Continue to descrip MCV?
A
- Incubation period: 2–8 weeks
- Causes pink, pearl-like lesions (1–5 mm in diameter) on the face (especially eyelids), arms, and legs
- Lesion has a dimple in the center.
- Scratching can cause lesions to spread
- Infection is usually self-limiting in individuals with a competent immune system.
- Can serve as a marker for severe immune deficiency
- Secondary bacterial infections are a complication of molluscum contagiosum.
- The smallpox vaccine does not prevent or protect persons from MCV infection.
17
Q
What is Vaccinia Virus?
A
- Used to vaccinate individuals against smallpox
- Also protects against monkeypox infection
- The exact origin of vaccinia virus is unknown.
- Genetically most similar to buffalopox
- Causes a localized skin infection
- May cause a severe and systemic disease in persons who are immunocompromised or have pre-existing conditions such as eczema or atopic dermatitis
18
Q
Describe the Lab diagnosis of poxvirus infections?
A
- 1949, last natural case of smallpox in the United States
- Very few physicians in the U.S. have seen an actual case of smallpox.
- Smallpox is a potential biological weapon.
- CDC has prepared information and instructions for physicians in case of a smallpox emergency.
19
Q
What is the Case Definition of Smallpox?
A
- Illness with acute onset of fever greater than or equal to 101oF
- Followed by rash of firm, deep seeded pustules
- Centrifugal pattern of lesions compared to chickenpox
20
Q
What are the preliminary tests for smallpox?
A
- Electron microscopy and virus isolation on scrapings of pustules and scabs done by state health laboratories
- ELISA assays
- PCR analysis is the only way to accurately distinguish between Variola, monkeypox, and vaccinia infections.
21
Q
What is the Cellular Pathogenesis?
A
- Very little is known about the pathogenesis and virulence of variola virus.
- The knowledge we have predates modern advances in molecular virology and immunology.
- Virtually no modern molecular biology has been applied to studying live virus
- Variola virus is stored safely in two international repositories (Must be worked within a BSL-4 maximum containment facility):
- CDC, Atlanta, Georgia, U.S.
- State Research Center of Virology and Biotechnology (Vector), near Novosibirsk, Russia
24
Q
What are the specific structures of a poxvirus?
A
External membrance
Lateral body
palisades
Core Envelope
Core DNA and associated proteins
Lateral Body
