Download Smallpox Melissa Mattison, M.D. October 22, 2002 SMALLPOX A

SMALLPOX
Melissa Mattison, M.D.
October 22, 2002
SMALLPOX
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A highly infectious disease
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Period of oral lesions and rash most infectious
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Spread via droplet nuclei, aerosols and direct contact
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Even bed-sheets of patients with the disease can transmit it
HISTORY
Responsible for many deaths over the course of history and used to account for 10% of deaths worldwide
The disease decimated the Native American population
Germ warfare was used by Lord Jeffery from England during the French and Indian War in the
1700’s, by dispensing blankets of victims of smallpox to the unsuspecting Native American
population
1796 – Edward Jenner noticed that dairymaids infected with cowpox gained immunity to smallpox and the
the first vaccination program began
1967 – WHO began a program to globally eradicate smallpox
1972 – USA stopped vaccinating against smallpox
1977 – The last case of documented smallpox was seen in Somalia
1980 – All countries supposedly destroyed their stocks of smallpox with virus remaining in only the USSR,
Great Britain and the CDC in Atlanta
EPIDEMIOLOGY
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Incidence is highest in Spring and Winter
Variola Major
-the classic description of smallpox
-30% mortality rate
-4 major varieties – Ordinary (most common), Modified (in previously immunized patients),
Hemorrhagic (uniformly fatal), Malignant (usually fatal)
Variola Minor (alastrim)
-1% mortality rate
MICROBIOLOGY
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A DNA virus
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Part of the genus orthopoxvirus. Other viruses in this genus include: monkeypox, vaccinia and cowpox
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Highly infectious with only a few virons required
PATHOGENESIS/CLINICAL PRESENTATION
Inoculation (12-14 days)
-via inhalation, spreads to regional lymph nodes where replication occurs. Asymptomatic viremia develops
on day 4, followed by multiplication of the virus in the spleen, bone marrow, and lymphatic system. By day
8, a second viremia develops along with fever and toxemia.
-the virus then localizes in small blood vessels in the dermis and beneath the oral and pharyngeal mucosa
Prodrome/Initial Symptoms (2-4 days)
-fever and malaise
-too sick to carry on normal activities
Days 1-4, The Rash
-first seen on tongue and in o/p. When these sores break, the virus is released in massive quantities in the
saliva and the patient is most contagious.
-Within 24 hours, the rash develops on the skin, first starting on the face and then the arms, legs and later
hands and feet.
-On day 3, the rash becomes raised bumps and by day 4 they are filled with opaque fluid with a depression
in the center.
Days 5-10
-Rash becomes pustular and firm to touch
Days 11-14
-Most of the pustules will scab over
Days 15-21
-Scabs fall off, leaving pitted scars, most pronounced on the face
-The person is contagious until all the scabs have fallen off
Beth Israel Deaconess Medical Center Residents’ Report
PRE-EXPOSURE PROPHYLAXIS
Vaccination – once and then in theory, every 10 years. Use a specialized bifurcated needle, a small but
exact amount of inoculum. 15 repeated punctures into the deltoid or thigh at right angle to the skin.
Vaccination + VIG (Vaccinia immune globulin) – to minimize vaccination side effects, only when absolutely
necessary. VIG is in very short supply and some say right now the rate limiting effect to widespread
vaccination in the USA.
The Vaccine- made of live vaccinia, another “pox” type virus. Vaccination site must be cared for
meticulously to prevent infection from spreading to others. The vaccine cannot give you smallpox, but it can
make you sick, especially if you have skin conditions or are immunocompromised. 1-2 deaths/million
vaccinated are expected and usually arise from post-vaccination encephalitis or vaccinia gangrenosa (when
the localized inflammation at the site of vaccination spreads through the body, causing widespread dermal
necrosis with involvement of the bone and adjacent tissues). 15/million vaccinated with have life-threatening
complications and 100s/million will have skin infections and rashes from the vaccine (non-life-threatening
complications).
Do not vaccinate people who have HIV, are immunocompromised due to cancer or immunosuppressant
medications (i.e., post-transplant), pregnant women, or people with children < 1 yo at home.
POST-EXPOSURE PROPHYLAXIS
-Vaccinate ASAP (up to 4 days after exposure can help)
-No antiviral agents are currently available
-Isolate the people suspected of having the disease
Do not admit to the hospital
Or – dedicated one hospital per region to victims
Vaccinate anyone who works in the hospital (or morgue) or anyone with face-to-face contact with
victim
If victims die, cremation is preferred
DIAGNOSIS
-Notify public health authorities immediately after any suspicion develops
-Characteristic Rash
Most dense in face and extremities
All lesions are at the same stage of development (in each region of the body)
-Obtain pustular/vesicular fluid
collected by person already vaccinate
put on cotton swab, into vacutainer tube, sealed with adhesive tape at juncture of stopper and the
tube and place in a second, durable, watertight container.
-Send to a BL-4 facility (capable of handling highly contagious fluid)
-Electron microscopy of the fluid will show brick-shaped virons
-PCR of the fluid will be positive for smallpox
References:
JAMA 281, 22: 2127-2137
JAMA 287, 9:1104
Mandell, Principles and Practice of Infectious Disease
www.cdc.gov
Of other potential interest:
Live satellite broadcast 11/6 12:45-3 pm, Smallpox: Recognition and Response, Sherman Auditorium
Beth Israel Deaconess Medical Center Residents’ Report