- Anthrax is a bacterial infection occurring worldwide, acquired through direct contact with infected animals or animal products, consumption of contaminated meat, or inhalation of airborne anthrax bacterial spores.
- Risk is very low for travelers.
- Symptoms of anthrax differ based on the mode of transmission and include itching and skin lesions covered by blackened dead tissue, nausea, vomiting, fever, and influenza-like illness.
- Consequences of infection can include respiratory failure, shock, infection of the blood and internal organs, inflammation of the brain membranes, and death.
- Prevention includes avoiding risk behaviors such as contact with infected livestock or animal products and consumption of contaminated meat.
- Anthrax vaccine is not routinely recommended for travelers unless otherwise indicated for occupational reasons. A preexposure vaccination series is 3 doses given over 6 months.
- Vaccine side effects are most commonly injection-site reactions, tiredness, headache, and muscle aches.
- Duration of vaccine protection declines over time after completing the series. A booster may be required annually or every 3 years (depending on risk) to maintain immunity.
- Postexposure prevention includes a vaccination series consisting of 3 doses given over 4 weeks, combined with antibiotic use.
Anthrax is a globally distributed bacterial disease that presents as cutaneous (most common), gastrointestinal, or inhalation anthrax depending on the route of transmission (skin contact, consumption, or inhalation). Domestic and wild animals may become infected when they inhale or ingest spores in contaminated soil, plants, or water, and the illness may be transmitted to humans upon contact with such infected animals or animal products. Risk is very low in travelers unless a bioterrorism event occurs. Anthrax disease can be prevented with vaccine, antibiotic, and antibody-based treatments given either before or after an exposure.
Anthrax occurs globally, but most commonly in impoverished agricultural regions with inadequate control programs for anthrax in livestock (e.g., herbivore mammals such as cattle, sheep, goats, camels, pigs, and antelope) in sub-Saharan Africa; central and southwestern Asia; the Caribbean; Central and South America; northern, southern, and eastern Europe; and parts of the Middle East. Occurrence of anthrax is uncommon in industrialized countries.
Worldwide, 2,000 to 20,000 human cases occur annually. In recent years large-scale animal outbreaks occurred in reindeer in Russia (2016) and in bison in Canada (2012).
Anthrax is transmitted via 3 major routes: skin, digestive tract, and lungs.
Skin infection (cutaneous anthrax) can result from direct contact with infected animals, animal products (e.g., meat, wool, or hides), or items made with such products (e.g., drum heads or wool clothing). This usually occurs in agricultural settings (e.g., ranches, slaughterhouses, veterinary clinics, butcher shops) or industrial settings (e.g., tannery/leather, wool, or hide processing factories). Cuts or abrasions on the skin increase susceptibility to infection.
Digestive tract infection (gastrointestinal anthrax), which is quite rare, may result from consumption of undercooked meat obtained from infected animals and tends to occur in family clusters or single-source outbreaks.
Lung infection (inhalation anthrax) results from inhalation of anthrax bacteria spores and is almost exclusively associated with intentional transmission through bioterrorism or biowarfare. It may also occur when anthrax spores are aerosolized while working with contaminated animal products such as wool, hair, or hides.
Risk is very low for travelers but increases for persons consuming contaminated meat or handling contaminated animal hide, wool, or other animal products, and for heroin users, laboratory workers, or populations typically targeted by terrorists.
Symptoms of anthrax most commonly appear within 7 days of exposure and may vary, depending on the mode of transmission.
Cutaneous anthrax begins with itching, followed by a painless, skin lesion (usually appearing on the face, neck, or arms) that changes from a bump to a blister then to an ulcer covered with blackened dead tissue (the hallmark sign of cutaneous anthrax). Fever, extreme tiredness, headache, and swollen glands may also occur.
Gastrointestinal anthrax affects all regions of the digestive tract from the mouth to the large intestine and is characterized by headache, nausea, vomiting, fever, and abdominal pain and tenderness.
Inhalation anthrax begins like a viral respiratory illness, followed by shortness of breath, mild fever, and muscle aches. Breathing becomes more difficult, and low blood pressure occurs.
Anthrax in injection-drug users (injection anthrax) commonly occurs as injection-site pain, swelling, and excessive bruising.
Consequences of Infection
Inhalation anthrax may result in shock and inflammation of the membranes around the brain. Rarely, gastrointestinal anthrax may spread and cause generalized infection of the blood and internal organs. Injection anthrax can spread throughout the body faster and may be harder to recognize than skin anthrax. Death occurs in 20% to 90% (inhalation anthrax) of symptomatic cases depending on the mode of transmission, time of treatment initiation, and medical management.
Need for Medical Assistance
Persons who have been exposed to anthrax or develop symptoms after travel (e.g., unexplained fever or new skin lesions) and persons with respiratory symptoms after exposure to an unknown white powdery substance should seek immediate medical attention for evaluation of the need for postexposure treatment. Animal-hide drum owners or players should report any unexplained fever or new skin lesions to their health care provider and describe any recent contact with animal-hide drums.
Vaccine, antibiotics, antibodies, or immune globulin must be started as soon as possible following exposure and may reduce the duration and severity of illness.
Travelers going to countries where anthrax is common and vaccine coverage of livestock is low should avoid:
- Direct or indirect contact with livestock, animal products, and animal carcasses
- Consumption of meat from animals of uncertain origin
- Consumption of raw or undercooked meat
- Returning home with animal products, trophies, or souvenirs that are prohibited by U.S. CDC, U.S. Department of Agriculture (USDA), or home/destination country’s authorities. See www.cdc.gov/anthrax/specificgroups/travelers.html for a map of anthrax-endemic areas and www.aphis.usda.gov/aphis/ourfocus/importexport for import regulations.
Preexposure vaccination is not indicated for travelers without other reasons for vaccination (e.g., military personnel or occupational exposure). Postexposure vaccination is recommended for unvaccinated persons who may have inhaled anthrax spores.
The most common side effects of anthrax vaccine include pain, redness, and swelling at the injection site. Occasionally, headache, fever, chills, and muscle aches occur. Serious side effects are rare but can include extensive swelling of the forearm.
Persons with underlying medical conditions or who have concerns about the vaccine should speak to their health care provider before vaccine administration.
The preexposure vaccination series consists of a primary series of 3 doses given at 0, 1, and 6 months. Booster doses are as follows:
- For persons at high risk of exposure: 2 booster doses should be given at 6 and 12 months after completion of the primary series. Subsequent follow-up boosters may be given every 12 months if risk continues.
- For persons not currently at high risk of exposure but who may have future high risk of exposure: A booster dose should be given every 3 years after completion of the primary series. If such persons need to immediately enter a high-risk area and 6 or more months have elapsed since the last dose of vaccine, an out-the-door booster and 2 weeks of antimicrobials should be given.
The postexposure series consists of 3 doses (given at 0, 2, and 4 weeks) plus antibiotics for at least 42 days. Antibody therapy may be indicated in some circumstances.