This vaccine is effective against bubonic plague, but probably not against aerosol exposure. Droplet Precautions for healthcare workers exposed to pneumonic plague. Fleas which live on the rodents can sometimes pass the bacteria to human beings, who then suffer from the bubonic form of plague. The pneumonic form of the disease would be seen as the primary form after purposeful aerosol dissemination of the organisms. The bubonic form would be seen after purposeful dissemination through the release of infected fleas.
All human populations are susceptible.
Recovery from the disease may be followed by temporary immunity. The organism will probably remain viable in water and moist meals and grains for several weeks. It also remains viable for some time in dry sputum, flea feces, and buried bodies but is killed within several hours of exposure to sunlight. The United States worked with Y. pestis as a potential biowarfare agent in the 1950's and 1960's before the old offensive biowarfare program was terminated, and other countries are suspected of weaponizing this organism. During World War II, there is reported evidence that Japan investigated the use of Y. pestis as a biological weapon.