Smallpox Flashcards
During the 17th and 18th centuries, how many people died of smallpox
~400,000 annually
What is the etiological agent of Smallpox
poxvirus
describe the etiological agent of smallpox
Complex and brick shaped, the largest known animal virus, linear double stranded DNA that encodes for 150-250 different proteins
what are the distinctive characteristics of the poxvirus
Usually large and complex, DNA genome replicates in cytoplasm using only virus-coded enzymes, replicates in cytoplasmic factories of the cell, and internal envelope not formed by budding but assembled de novo.
What is smallpox also known as
Variola Virus
Variola Major, classic disease of ancient times, has a mortality rate of ___
10%-30%
Variol Minor, the less severe form of smallpox, has a mortality rate of __
~1%
How is small pox transmitted
Humans being the only natural host, it can be transmitted by aerosols, physical contact with vesicles, or fomites (bedding or clothing)
Describe the pathogenesis of smallpox
Infection of oropharynx via infected aerosols and spreads to regional lymph nodes. An asymptomatic primary viremia via infected macrophages. Virus spreads to spleen, bone marrow, other lymph nodes, and small blood vessels of skin and oropharngeal mucosa. A secondary viremia occurs followed by onset of clinical signs and symptoms, vesicles on skin and oropharynx.
About when does the asymptomatic primary viremia occurs
3-4 days after primary infection
____ occurs by day 8-12 after primary infection
Secondary viremia
When do you normally start to see vesicles form on skin
day 14
What is the incubation time for smallpox
12-14 days on average but can range from 7-17 days
what is used to distinguish smallpox from other rash illnesses
smallpox has a prodrome phase that appears before onset of rash and lasts 2-4 days.
what happens during the prodrome phase
abrupt fever (>101F) headache, nausea, vomiting, and malaise
During what time of clinical disease is a person most infectious
during the time there are small red spots on tongue and mouth which ulcerate and release large amounts of virus into saliva.
How long does the most infectious stage last
4 days
when does the most infectious stage begin
~24 before onset of rash on skin
How does the rash spread on the body
in a centrifuge distribution, outward in.
what is the clinical progression of disease
by the 3rd day the macules become papules. Then the 4th day the papules become vesicles filled with thick opaque fluid that contains infectious virus. Fever rises again and remains high until scabs from on vesicles to form pustules. Pustules are raised, round, firm to the touch and mature and reach maximum size by 7th-10th day. By day 10 the pustules begin to crust over and scab at the 14th day.
how are smallpox distinguished from chickenpox
Smallpox vesicles have a depression in the center, umbilication.
why does smallpox lesions have depimentation and pitted scars
because the sebaceous gland (sweat glad) of the skin has been destroyed
what is the suspected cause of death in smallpox and when does it usually occur
It’s suspected multiple organ failure due to immunopathogenesis or over whelming viremia and secondary bacterial infections and sepsis; 10-16 weeks of clinical illness
the small pox vaccine virus is termed
vaccinia
