Smallpox was once a feared and highly contagious viral disease that was found in all countries around the world. The main characteristic of the disease was a rash of blisters or pustules on the skin, which eventually dried up and left permanent scars. Smallpox can be deadly if the virus attacks the circulatory system, bone marrow or respiratory system.
As recently as the s, around 12 million people caught this highly contagious disease and approximately two million people died every year. The World Health Organization WHO mounted an aggressive worldwide campaign of immunisation and by , the last naturally occurring case was detected in Somalia. Eradication was certified by a commission of scientists in and endorsed by the World Health Assembly the following year.
Small stocks of smallpox virus remain in two designated international laboratories. Vaccination against smallpox is not recommended in Australia and is not on the National Immunisation Program Schedule. The smallpox virus incubates inside the body for between seven and 17 days, usually for 12 days. Symptoms include:. Death can result if the virus attacks the circulatory system, bone marrow or respiratory system.
Smallpox has played an important role in the development of vaccination. Since ancient times, it was common knowledge that an infection with smallpox conferred lifelong immunity. An 18 th century doctor, Edward Jenner, first discovered the key to immunising people against smallpox.
Using a similar technique to that used by Jenner, researchers devised an effective smallpox vaccine based on a similar virus, called the vaccinia virus. Different formulations of this vaccine were used until the s. In , the World Health Organisation mounted a major campaign to eradicate smallpox. Within 12 years, smallpox disease was eradicated. Smallpox has recently been assessed as a possible biological weapon that could be used in non-conventional warfare or in a terrorist attack.
Although this is believed to be unlikely, planning for such an eventuality has commenced worldwide. In Australia, a small amount of smallpox vaccine is available for essential medical personnel and contacts in the case of an outbreak.
Immunisation has saved more lives this century than any other medical discovery, including antibiotics. Many infectious diseases have been contained by immunisation programs. For instance, cases of invasive haemophilus influenzae b Hib disease in Victoria have declined by more than 90 per cent since vaccination was introduced in These spots will also develop on the chest and abdomen but are much less numerous than those seen on the head, neck and limbs.
These macules will all appear within 24 hours. The red spots will all at the same time develop into red bumps papules after about three days. By the fourth day, the all the papules will fill with a thick, opaque fluid and have a depression in the center. These skin lesions are now called pustules. Their fever will rise again at this time and remain high until scabs form.
In time all the pustules will break open and a crust will form over the skin lesions followed by a scab. On day 14 of the rash the skin lesions will scab over. All the skin lesions will go from macule, to papule, to pustule, to crust, to scab at the same time and it will take about 17 days for this to occur. People with smallpox are infectious to others until all the scabs have fallen off.
When t he scabs fall off they leave marks on the skin that eventually become pitted scars. The skin rash takes about three weeks to complete macule to last scab falling off. People with the hemorrhagic form of Variola major do not develop the same rash as in ordinary Variola major.
Following the prodrome the skin on the chest and abdomen will turn a purplish red dusky erythema. The capillaries in the skin will then leak blood into the skin. It will start out as small dots petechiae that will get larger purpura and larger ecchymoses. Nearly everyone with this form of Variola major will die. The flat form of Variola major was also nearly always fatal. After the prodrome the skin would develop a dusky erythema that would then slowly become papules.
Sometimes the papules would become blisters. The fever in the prodrome does not go away as in ordinary Variola major. The skin lesions do not crust or scab over but rather the skin will peel away in sheets. Usually death occurred during the second week of the illness. Why is smallpox an attractive BW? Even if the person does not die they are very ill for a couple of weeks. Less than 10 viruses are needed to start an infection.
Those viruses are most likely to result in disease when inhaled. Aerosol exposure of less than 15 minutes is sufficient to cause an infection.
Symptoms of infection do not start for days. Person-to-person transmission of this disease is common and many more people would be infected. An aerosol of the organism would be very effective way of infecting many people at one time. The virus is not very hardy. It will only last a couple of hours at high temperatures and high humidity. Yet, even indoors the virus only lasts for about 2 days.
Occupying an area contaminated with smallpox would not require decontamination as long as those occupying the area waited until all the virus had become inactivated.
Laboratory Diagnosis. These swabs will then need to be sent to a laboratory that is prepared to handle this very hazardous sample.
The swab can be examined for the presence of virions using an electron microscope, techniques to look for small amounts of Variola DNA polymerase chain reaction; PCR , or by using antibodies specific for the virus to detect it or by growing the virus on live cell cultures. Blood samples may be obtained to look for antibodies to the Variola virus.
Initial treatment involves isolating the person from others and maintaining that isolation for at least 17 days. If given early within days of exposure to the virus, vaccination can significantly lower the severity of or prevent smallpox disease. Diligent supportive care should consist of adequate nutrition and hydration, eye care, and treatment to prevent secondary bacterial skin infections.
Cidofovir is an antiviral drug that may be beneficial if given in the early stages of illness, although the effectiveness of this treatment has not been proven in humans. Infections of the cornea of the eye may be treated with topical idoxuridine. Anyone who had contact with someone who developed an infection would need a smallpox vaccine, which can prevent or lessen the severity of the disease if given within four days of exposure to the smallpox virus.
Two vaccines are available. One vaccine ACAM uses a live virus that's related to smallpox, and it can occasionally cause serious complications, such as infections affecting the heart or brain. That's why it's not recommended that everyone be vaccinated at this time. The potential risks of the vaccine outweigh the benefits, in the absence of an actual smallpox outbreak.
A second vaccine, a modified vaccinia Ankara vaccine Jynneos , has been found to be safe, and it can be used in people who aren't able to take ACAM, who have weakened immune systems or who have skin disorders. Immunity or partial immunity after a smallpox vaccine may last up to 10 years, and 20 years with revaccination.
If an outbreak ever occurred, people who were vaccinated as children would still likely receive a new vaccination after direct exposure to someone with the virus.
Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version. This content does not have an Arabic version. Overview Smallpox is a contagious, disfiguring and often deadly disease that has affected humans for thousands of years.
Smallpox Open pop-up dialog box Close. Smallpox These are smallpox lesions on the skin of the trunk. Request an Appointment at Mayo Clinic.
Share on: Facebook Twitter. Show references Friedman HM, et al. The epidemiology, pathogenesis and clinical manifestations of smallpox. Accessed Feb.
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