Week 2- Columbian Exhchange (Smallpox & Monkeypox) Flashcards
What are characteristics of Poxviridae viruses, like Smallpox?
- generally brick shaped
- large compared to other viruses
- complicated internal structure (linear, double-stranded DNA)
- member are antigenically very similar (important for vaccination)
What family of viruses does Smallpox belong to?
Poxviridae
How is smallpox transmitted?
- inhalation (close contact, over a short distance)
- incubation time of 10-12 days
What are the symptoms of smallpox?
- flu like illness for 2-4 days
- fever, myalgia, malaise, headache all followed by rash (which causes scarring)
- about 30% mortality
What are some of the complications that arise from smallpox?
Secondary bacterial infection of skin, arthritis, loss of vision, encephalitis
What are the two types of severe smallpox?
Flat-type and hemorrhagic
What are the symptoms of flat-type smallpox?
- flu like stage is generally more severe (prolonged fever)
- rash does not progress to vesicular stage
- usually fatal
What are the symptoms of hemorrhagic smallpox?
Early subtype: rash does not progress to vesicular stage, bleeding under skin and into internal organs, always fatal
Late subtype: hemorrhages into the base of vesicles, usually fatal
What affects the severity of smallpox?
Infectious does (higher dose=more severe)
In what ways is smallpox an ancient disease and what did ancient cultures know about smallpox?
- existed since about 10,000 BC in Africa, from there spread to Europe and Asia but Americas remained smallpox free
- many cultures have deity dedicated to smallpox
- knew those with scars didn’t become infected again and that those infected through scratch in the skin tended
Describe variolation.
- intentional introduction of pus or scabs from smallpox lesions into a naive host
- China (nasal route), India (skin scratch)
- tended to cause less severe disease (<2% mortality)
Explain the course smallpox took when it spread through South and Central America
- Hispaniola (1507, 1517, 1518, 1519): outbreaks associated w/ slave trade, ~1:3 natives died
- Cuba/Puerto Rico (1518/1519): about 50% mortality
- Aztecs (1519): killed about half of Aztecs
- Incas (1524): killed about 200,000
- Brazil (1555, 1560, 1562, 1563): repeated outbreaks, killed 50% or more of natives
- By 1558 repeated epidemics all over S. America, including deep into Native territory
What effect did the introduction of smallpox have on South/Central America?
- native populations in Caribbean essentially wiped out, replaces by Spaniards and African slaves
- Aztecs & Incas were defeated
- now, natives make up only a small portion of population in these areas
Describe the spread of smallpox in N. America.
- much less densely populated than Mexico/Peru
- 1617: smallpox kills many natives of Massachusetts, repeated outbreaks follow, potentially killed 50% of affected tribes
- 1721: variolation introduced, helps prevent disease in colonists but not natives
- 1785: affected the Sioux and crossed the Rocky Mountains, reported in CA and AK
- 1801 & 1836: massive epidemics, virtual extinction of many tribes
What factors led to the emergence of smallpox in America?
- migration, both voluntary and forced (slavery)
- movement of military personnel
- international travel
How did social disruption affect the mortality rates of smallpox?
large portions of populations were sick at the same time, few people left to tend to basic needs (food, water, care, etc), some may have fled from sick or avoided them
Why was smallpox so deadly in the Americas, particularly in Native populations?
Likely: Social disruption, host behavior in ordinary times, maternal antibodies
Unlikely: pregnant women, genetic impairment, genetic homogeneity, malnutrition
How did host (human) behavior cause smallpox to be more deadly in Native populations?
- customs may have contributed to spread of disease
- large community dwellings, little fear of getting infected from the sick (often visiting sick or sleeping in the same dwelling)
- led to enhanced transmission and increased infectious dose
Explain the timeline for smallpox eradication.
- WHO resolves to eradicates in 1958, last community acquired case occurred in 1977 (there were 2 lab cases in ‘88)
- ‘76 WHO asks that all labs create registry of smallpox samples, asks for destruction of unnecessary stock; ‘83 all known samples either in ATL CDC or Moscow, Russia; ‘86 WHO recommends that all remaining stock be destroyed, this has yet to occur
What type of virus is monkeypox?
orthopox virus
How did monkeypox emerge in monkey colonies?
First reported in Denmark (1958), 9 subsequent outbreaks in monkeys over next ten years, many primates affected but none of the handlers became ill
How did monkeypox emerge in humans?
- First case reported in Central Africa (1970), likely that there were earlier infections that were just misdiagnosed
- Dramatic increase in # of cases in mid-‘90s, increased spread among humans and decreased mortality
How did monkeypox reach the US and what was the result?
- infected rodents imported from Africa (Gambian pouch rats, African door mice, rope squirrels)
- black tail prairie dogs became infected
- resulted in 11 infections, 0 deaths
- occurred in 2003
What is the progression of monkeypox?
- progression very similar to smallpox
- 10 to 15% mortality
How do the cases of monkeypox in Central Africa and Western Africa/United States differ?
- C. Africa: more severe form, 80% of infections in children < 10 years, mostly affects males, previous vaccination for smallpox is effective
- W. Africa/US: less severe, more normal age/sex distribution, lower viremia, prior vaccination not protective
How is monkeypox transmitted?
- mode of transmission for natural infection is not certain
- associated w/ contact w/ infected animals (zoonosis)
- can be transmitted through inhalation in lab animals
- poorly transmitted among humans (though this could be changing due to mutation)
What treatment exists for monkeypox?
currently only supportive care
How does monkey pox interact with the immune system?
- infected cells inhibit recognition by CD4+ and CD8+ T-Cells
- general immune suppressant
- T-cells are unable to respond to other infections
- infected cells also inhibit recognition by NK cells
What factors led to the emergence of monkeypox?
recognition of a new illness, decrease in vaccination (for smallpox), international travel, possibly evolution of infectious agent
How well is monkeypox being surveilled?
Not that well. Factors limiting surveillance in C. Africa include civil unrest, military action, poor public health infrastructure, cross reactivity of many pox viruses
