Smallpox. Houston Academy of Medicine - Texas Medical Center Library. From the SelectedWorks of Richard N Bradley

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1 Houston Academy of Medicine - Texas Medical Center Library From the SelectedWorks of Richard N Bradley September, 2007 Smallpox Richard N Bradley, The University of Texas Health Science Center at Houston Available at:

2 SMALLPOX Richard N. Bradley, MD The University of Texas Health Science Center at Houston Medical School, Department of Emergency Medicine December 3, Kelley St., Ste 1EC93006 Houston, TX, United States of America Telephone: Facsimile: Keywords: Smallpox; Disease Outbreaks; Bioterrorism Copyright 2006 Richard N. Bradley

3 KEY FACTS Description Viral infection of the human respiratory tract. Causes Infection by variola virus. Risk Factors Exposure to a biological warfare or bioterror attack or contact with an infected person. Symptoms Fever, cough and body aches, followed by a spotted, bumpy rash. Diagnosis Confirmed by testing blood or the fluid from the blisters. Treatments None currently approved but experts are testing some medications. Pathogenesis The virus enters and multiplies in the respiratory passages. Prevention Avoid those with the disease. During an outbreak a vaccine is available that will prevent the disease or lessen its severity. Epidemiology Completely eradicated from nature, but could be a potential biological weapon.

4 Smallpox first appeared over 3,000 years ago. The first cases probably occurred in India or Egypt. It eventually spread and became one of the most devastating diseases known to humanity. For centuries, repeated epidemics swept across continents, wiping out populations and changing the course of history. Even in the 1700 s smallpox killed one out of ten children born in Sweden and France and one out of every seven children born in Russia. Fortunately, in 1798, an English physician named Edward Jenner showed that inoculation with a similar virus, cowpox, could protect a person against smallpox. This vaccine led to a global eradication program. This effort was completely successful vaccination eliminated naturally occurring smallpox from the world. The last case was in Somalia in Several laboratories maintained stocks of the virus in storage after the eradication of the disease. Eventually, these storage sites consolidated, and by 1984, they had centralized the remaining stocks at the Centers for Disease Control and Prevention (CDC), in Atlanta, and the Research Institute of Viral Preparations, in Moscow. In 1994, the storage site in the Soviet Union was moved to the State Research Centre of Virology and Biotechnology (the Vektor Institute), in Novosibirsk, Russia. This centre may have been vulnerable when the Soviet Union collapsed in the early 1990 s. Many experts are concerned that someone may have misappropriated some of the virus that causes smallpox during this time. If this happened, smallpox could pose a significant bioterrorism threat. The virus is easy to grow and experts could probably modify it in a way that protects it from heat. It can survive in aerosol form and thus someone could load it into weapons or deliver it from a spray device. Today many countries are preparing to deal with a potential attack using smallpox. Causes and risk factors The variola virus causes smallpox. It affects only humans and is very contagious. It usually spreads from person to person by tiny droplets created when an infected person coughs. Contaminated clothes and bedding can also spread the disease, but the risk of infection from these sources is much lower. Although direct face-to-face contact is usually required for smallpox to spread from person-to-person, the disease does spread relatively easily. Estimates are that for every one person who initially develops smallpox after a bioterrorism attack, ten more will develop the disease from person-to-person transmission. Before 1970, almost everyone in the world had some immunity against smallpox. Either they had been infected and survived, which gave them natural immunity, or they had received a vaccination that gave them artificial immunity. These people may have some protection in the event of a future smallpox outbreak, but no one knows how long protection lasts after a smallpox vaccination. Some experts recommended revaccination every ten years. Health officials, however, discontinued all of the routine vaccination programs after they eradicated the disease. Only a very few people have received a vaccination against smallpox since Therefore, almost no one in the world has any immunity that would provide protection in a future smallpox outbreak.

5 During previous decades when smallpox was occurring, about three out of ten cases of smallpox among individuals without immunity were fatal. Even though most people in the world probably do not have any immunity today, advances in modern health care might moderate the relatively high fatality rate. Symptoms and signs Smallpox, like many infectious diseases, has an incubation period. During this time, the virus is multiplying in the person s body, but he or she looks and feels healthy and cannot infect others. The incubation period for smallpox is from seven to seventeen days, but for most people, it will be between twelve and fourteen days. After the incubation period, the infected person will quickly become very ill with flu-like symptoms. These include fever, weakness, headache, and muscle and joint pain. Two to three days later, the fever improves and the patient feels somewhat better. At this point sores develop in the person s nose and mouth. These become raw and release large amounts of virus. Each cough propels large numbers of these virus particles into the air. Next, the characteristic rash appears, first on the face, hands and forearms and then after a few days moving to the chest, abdomen and back. The rash starts as pink bumps. The name smallpox comes from the Latin word for spotted and refers to these bumps. They eventually become blisters and then fill with pus. After several days, they dry up and form scabs. Treatment and prevention There is no effective treatment for smallpox, although many different medications are under investigation. Since there is no cure for smallpox, medical treatment is limited to caring for complications of the disease, such as shock or respiratory failure. People who have been around smallpox but have not yet started to have any symptoms can receive the smallpox vaccination. If given soon enough, it can prevent the disease or reduce its severity. In the event of an outbreak, many governments have stockpiles of the smallpox vaccine that they could use. The governments of both the United Kingdom and the United States, for example, have enough to vaccinate the entire population of their countries, if necessary. Another important step to stop the spread of a future outbreak will be to ensure healthy people stay away from those who are sick. Those with smallpox must be isolated until the last scab comes off their bodies. In a large outbreak, infected individuals will be encouraged to stay at home to help reduce the spread of the disease. Public health authorities may recommend social distancing, or asking people to avoid crowded places, to reduce the spread of smallpox. In the event of a smallpox outbreak, it is important that the public stays informed. Public health officials will share important information including areas where they have found smallpox cases and who to call and where to go if someone thinks they have had a smallpox exposure.