DSI Newsletter: Smallpox

DSI Newsletters, Issue 16:
Smallpox

Smallpox awareness has come to the forefront since September 11, 2001, as a possible weapon of bioterrorism. Prior to its eradication, it was considered the most devastating of all the infections diseases. Smallpox is a contagious, disfiguring, and sometimes (30%) deadly viral disease caused by the variola virus, a member of the Orthopoxviruses. It's believed that it first appeared in northeastern Africa and the Indus Valley of southcentral Asia nearly 12,000 years ago and became a worldwide problem until it was eradicated in the late 1970s. Its incubation period is about 12 days. Its mode of transportation is person to person by infected saliva droplets or it may be transmitted by fomites (contaminated clothing or bedding). It's most infectious during the first week and remains so until the scabs fall off. The initial symptoms are similar to the flu, including fever, fatigue, head and back aches, vomiting, diarrhea, the classic rash beginning on the face and spreading. Initially, the rash may be confused with that of varicella (chickenpox). Typically, about 30% of the people who contact the virus die from it. There is no known antibiotic (antiviral) to kill this virus.
The global eradication of smallpox is considered one of the greatest achievements of modern medicine. Smallpox hasn't occurred naturally in the US since 1949. Routine vaccination against it ended in 1972. We were recommending the shot every ten years. Though the disease was eradicated off our streets over 20 years ago, several samples of the live virus were preserved for research purposes. Now fear that this terrible virus that we said was gone may be sprayed on us by our enemies. The deliberate reintroduction of the variola virus across our planet would clearly be the worst crime against humanity ever since that asteroid 45 million years ago struck our planet!

There are a few types of variola viruses. Variola major, which caused severe illness and killed about 30% of infected persons. Variola minor, which caused a much milder form of the illness and had about a 1% death rate. Two less common forms of the disease were even more deadly. Malignant smallpox, with its flat velvety lesions caused death in more than 96% of affected people. And especially in pregnant women, hemorrhagic-type smallpox, which caused bleeding and death within a week. There is some evidence that Russia was working on modifying the smallpox virus to make it particularly more virulent (more contagious and deadly) to be used as a bioweapon of mass destruction.
Even though we stopped giving out the vaccine in 1972, we did stockpile about 15 million doses. None is currently available to the general public other than that in an experiemental vaccine trial. One done recently by the NIH diluted the old vaccine five to one with water to stretch it out more. More drug studies are being planned to make a smallpox vaccine available to everyone again.
Smallpox is only found in humans (very occasionally in monkeys). There is no other reservoir. That's why we thought we took it off our planet. An English physician named Edward Jenner in 1796 became the first physician to discover a vaccine. And the one he discovered was the smallpox vaccine! He observed that many milkmaids who contracted cowpox, a disease in cows that causes only mild illness in humans, either did not contract smallpox or got an attenuated disease (milder form). He experimented by taking the fluid from a cowpox blister on a milkmaid's hand and administered it to a young boy through incisions on his arm. The boy was then protected from smallpox. It's interesting that the word "vaccine" comes from the Latin word for cow, vacca, illustrating its etymology in cowpox and how it helped to prevent smallpox. The vaccine we were using in modern times was a close cousin to cowpox was called the Vaccinia virus. It causes a protective immune response to ward off smallpox. It doesn't contain any smallpox, only live Vaccinia virus.
The smallpox vaccine was first mandatory in Massachusetts back in 1809 for everyone. Wyeth Laboratories discontinued production in 1981 and removed it from the market in 1983. Routine vaccination of US military personnel stopped in 1990. Today, only laboratory workers at risk for exposure to the virus or people willing to join an experimental investigation on the next generation smallpox vaccine can be vaccinated. In the event of a smallpox epidemic, vaccination within four days of exposure can offer some protection. When the vaccine was routinely administered here, we would avoid its use in people with eczema, weakened immune system and household contacts, HIV, pregnancy, and people with a previous serious adverse event from a vaccine. If a bioterrorist act with smallpox occurs, we will probably vaccinate everyone.

The smallpox vaccine was adminstered by making 15 punctures through the skin with a special needle. The patient had to come back a week later to see if they had a successful injection site reaction (take). That is a reaction severe enough to indicate that the person is immune to the disease. More than 95% of vaccine recipients are protected against smallpox for five years and, with revaccination immunity, anywhere up to 30 years.
Many side effects from the smallpox vaccine were common. Immunized people frequently develop swollen and tender lymph nodes that can last for two to four weeks after the vaccination site has healed. Fever and rashes were more common with children. About five per 10,000 immunized inadvertently infect another part of their bodies with the live vaccinia virus (smallpox vaccine), which may result in serious injury or death. Vaccinia infection of the skin of people with eczema and an often fatal reaction known as vaccinia necrosum occurs in less than one per 10,000. Children under one year had a one in 10,000 risk of causing an inflammation of the brain. Susceptible people coming into contact with someone's vaccination site before it heals can get the vaccinia virus about 27 per 10,000 immunized. When this occurs, we have a way of providing the patient with temporary immunity with the use of VIG (Vaccinia Immune Globulin). There's a similar product for hepatitis B called HBIG (Hepatitis B Immune Globulin). This helps to treat side effects by giving the patient passive immunity for a short time. It was decided back in 1972 that we would stop providing the smallpox (vaccinia) vaccine because the risk of smallpox was unheard of back then. If a mass campaign to vaccinate Americans against smallpox were in place today, about 250 people might die as a side effect of the shot and several thousand more would have side effects. However, in the event of a bioterrorist attack, then the benefits would exceed the risks (encephalitis or brain swelling, progressive vaccinia in which the sore on the arm spreads without healing, and eczema vaccinatum in people with eczema, all of which could be fatal).
Hopefully, we will never see smallpox again. If we need to revaccinate everyone, hopefully future investigational new drug trials will help us obtain safer alternatives.

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