Facts About Anthrax and Smallpox as Bioterrorism Weapons

Concern about deliberate use of disease agents as bioterrorism weapons presently focuses on anthrax and smallpox, although there have been no smallpox attacks to date. As part of its bioterrorism-response plans, the US Centers for Disease Control and Prevention (CDC) is currently expanding its stockpiles of pharmaceuticals and other medial supplies.

Anthrax

Anthrax is an acute infectious disease caused by a spore-forming bacterium. The serious forms of human anthrax are inhalation anthrax, cutaneous anthrax and intestinal anthrax. Symptoms of disease vary depending on how the disease was contracted, but usually occur within seven days after exposure. Initial symptoms of inhalation anthrax infection may resemble a common cold. After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax is often fatal.

Cutaneous anthrax may occur when the skin surface is exposed to the bacterium and a sore or swelled area appears on the skin. A central area of ulceration develops and a very dark, brownish scab forms. It can be painless and it may be accompanied by a fever.

The intestinal disease form of anthrax may follow the consumption of contaminated food and is characterized by an acute inflammation of the intestinal tract. Initial signs include nausea, loss of appetite, vomiting, and fever, followed by abdominal pain, vomiting of blood, and severe diarrhea.

Direct person-to-person spread of anthrax is extremely unlikely, if it occurs at all. Therefore, there is no need to immunize or treat people who have had contact with persons ill with anthrax, such as household contacts, friends, or coworkers, unless they also were exposed to the same source of infection.

In persons exposed to anthrax, infection can be prevented with antibiotic treatment. Early antibiotic treatment of anthrax is essential - delay reduces chances for survival. Anthrax usually is susceptible to Ciprofloxacin (or Cipro), penicillin and doxycycline.

The course of action for preventing anthrax after exposure in the civilian population is the use of antibiotics. Vaccination is not recommended, and the vaccine is not available to health care providers or the general public. The CDC does not recommend that physicians prescribe anthrax antibiotics for the general public at this time. Currently, the CDC has enough antibiotics to prevent the disease in two million people exposed to anthrax and intends to increase this to six million.

Patients with cutaneous anthrax have reported case fatality rates of 20% without antibiotic treatment and less than 1% with it. The case-fatality estimates for inhalation anthrax are based on incomplete information, but are extremely high even when appropriate antibiotics are given. For gastrointestinal anthrax, the case-fatality rate is estimated to be 25%-60%, and the effect of early antibiotic treatment on that case-fatality rate is not known.

Smallpox

Smallpox infection was eliminated from the world in 1977, but some disease experts fear that it could be a significant weapon if developed and utilized for bioterrorism.

Smallpox is caused by variola virus. The average incubation period following exposure is about 12 days, ranging from seven to 17 days. Initial symptoms include high fever, fatigue, and head and back aches. A characteristic rash, most prominent on the face, arms, and legs, follows in two to three days. The rash starts with flat red sores that develop at the same rate. Lesions become pus-filled and begin to crust early in the second week. Scabs develop and then separate and fall off after about three to four weeks. The majority of patients with smallpox recover, but death occurs in up to 30% of cases.

Smallpox is spread from one person to another by infected saliva droplets that expose a susceptible person having face-to-face contact with the ill person. Persons with smallpox are most infectious during the first week of illness, because that is when the largest amount of virus is present in saliva. However, some risk of transmission lasts until all scabs have fallen off.

Contaminated clothing or bed linen could also spread the virus. Special precautions need to be taken to ensure that all bedding and clothing of patients are cleaned appropriately with bleach and hot water. Disinfectants such as bleach and quaternary ammonia can be used for cleaning contaminated surfaces. The smallpox virus is fragile and in the event of a bioterrorist aerosol release (sprayed into the air), all smallpox virus lingering in a building will be inactivated or dissipated within 1-2 days.

Routine vaccination against smallpox ended in 1972 and is estimated to last only three to five years. The level of immunity, if any, among persons who were vaccinated before 1972 is uncertain; therefore, these persons are assumed to be susceptible. Vaccination against smallpox is not recommended to prevent the disease in the general public and therefore is not available.

In people exposed to smallpox, the vaccine can lessen the severity of or even prevent illness if given within four days after exposure. In the event of an outbreak, the CDC has clear guidelines to swiftly provide vaccine to people exposed to this disease. The US supply of vaccine is securely stored for use in the case of an outbreak. In 2000, the CDC awarded a contract to a vaccine manufacturer to produce additional doses of smallpox vaccine.

There is no proven treatment for smallpox, but research to evaluate new antiviral agents is ongoing. Patients with smallpox can also benefit from supportive therapy (intravenous fluids, medicine to control fever or pain, etc.) and antibiotics for any secondary bacterial infections that occur.

Information provided by the US Centers for Disease Control.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.