The agent that causes tularemia, Francisella tularensis, is one of the
most infectious bacteria known: inhaling as few as ten microscopic germs can
trigger disease. A World Health Organization committee estimated that if 110
pounds of a virulent strain of the bacteria were sprayed over a city of five
million, it could incapacitate 250,000 people and kill 19,000. Respiratory
failure or shock would cause most fatalities.
During World War II, both the Japanese and U.S. militaries researched
tularemia. In the 1990s, the Soviet Union developed antibiotic- and
vaccine-resistant strains.
Tularemia occurs naturally in small mammals such as mice, squirrels, and
rabbits. Human infection, which is rare, can result from insect bites or
handling infected animals. It is possible that infected flies, ticks, or
mosquitoes could intentionally be released as weapons, but direct spraying of
the bacteria is thought to be a more likely threat.
Symptoms
Various forms of the disease all begin with the sudden onset of flu-like
symptoms:
fever, chills, headache, cough, and lethargy
Additional symptoms depend on the form but include:
swollen and sore lymph nodes
skin ulcers
red and sore eyes
abdominal pain, diarrhea, and vomiting
pneumonia
How it would be spread
Aerosol or food. Human-to-human transmission has not been documented.
Treatment
Early antibiotic therapy is effective, and if started within 24 hours of
exposure, may prevent disease. A variety of antibiotics can be used, although
some antibiotics may be powerless against strains genetically engineered to be
resistant.
Vaccine
No vaccine is available for the general public. The U.S. Food and Drug
Administration is investigating a vaccine that is now available for high-risk
lab workers.
Deer flies can carry tularemia and cause natural cases of human infection.
