Tularemia Cases on the Rise in Colorado

Jul 3, 2015 | Noushin Berdjis | Outbreak News

Health officials are alarmed about a recent increase in the number of Tularemia cases in Colorado. Between 1983 and 2013, the average number of reported tularemia cases in Colorado was around four per year, but last year saw a drastic increase to 16 cases [1-3]. There have already been 11 reported cases in the first half of 2015 [1-5].

The most recent cases occurred last week, when two individuals from Weld County contracted this highly infectious bacterial disease, also known as ‘rabbit fever’ [1,3]. It is suspected that they were exposed to the bacteria while mowing or working in their yards [1]. One of the patients is still in the hospital while the other is recuperating at home [3].

Health officials in Colorado are expecting future cases because tularemia is capable of persisting in the environment and is also able to survive the colder winter months [2]. Additionally, climate may play a role as rainfall creates more vegetation, which results in the proliferation of rabbits and rodents. The increased rodent population leads to increased opportunities for transmission of tularemia between animals and humans [2].


What is Tularemia?

Tularemia is caused by the Francisella tularensis bacteria, and is capable of infecting both animals and humans [6]. Animals such as rabbits, hares, and rodents are particularly susceptible to the bacteria [6]. There are several ways in which humans can become infected and symptoms vary depending on the route of transmission [6]. Humans are infected by exposure to the bacteria via the skin, eyes, mouth, throat or lungs [6]. More specifically, the bacteria can be transmitted to humans through direct or indirect contact with an infected animal, such as handling infected animal tissue; through the bite of an infected tick or deer fly; contact with contaminated soil; or ingesting contaminated water [6]. Humans can also become infected by inhaling contaminated dusts or aerosols. This route of transmission is most common among farmers or individuals conducting landscaping activities and generally occurs as a result of running over an infected animal carcass with a tractor or lawn mower [6]. This route of transmission results in pneumonic tularemia [6].

Symptoms for pneumonic tularemia include fever, cough, chest pain and difficulty breathing [7]. While pneumonic tularemia is the most serious form of the disease, ulceroglandular tularemia is the most common [7]. This form of the disease is caused by transmission via a tick or deer fly bite or through direct contact with an infected animal. Symptoms include fever, swelling of the lymph glands, and the appearance of a skin ulcer at the portal of entry [7]. Oropharyngeal tularemia occurs if the individual became infected by eating or drinking contaminated food or water. Symptoms include a sore throat, mouth ulcers, tonsillitis, as well as swelling of the lymph nodes [7].

All forms of tularemia are successfully treatable with antibiotics [1-6]. However, if left untreated the infection can lead to hospitalization and possible death. Fortunately, person-to-person transmission of tularemia has not yet been reported [6].



The Centers for Disease Control, as well as the Colorado Department of Public Health and Environment have released the following recommendations for preventing tularemia exposure and infection [1-6]:

  • Wear insect repellent when going outdoors;
  • Avoid contact with wild animals such as rabbits, squirrels, and voles;
  • Avoid walking barefoot in areas where such animals are frequently found;
  • Prevent pets from hunting wild animals that may be infected;
  • Wear gloves and dust masks when conducting yard work or handling sick or dead animals.

Ultimately, it is best to avoid direct contact with animals such as rabbits, squirrels, voles and rodents. Additionally precautious should be used when conducting outdoor activities and individuals should be aware of tularemia symptoms.






  1. http://www.denverpost.com/news/ci_28374467/colorado-health-officials:-tularemia-cases-on-recordbreaking-pace
  2. http://www.dailycamera.com/lafayette-news/ci_28203252/lafayette-resident-contracts-tularemia-after-mowing-lawn-dies
  3. http://denver.cbslocal.com/2015/06/24/colorado-sees-2nd-highest-number-of-rabbit-fever-cases-since-1983/
  4. http://www.9news.com/story/news/health/2015/06/24/colorado-tularemia-cases/29227791/
  5. http://denver.cbslocal.com/2015/06/24/colorado-sees-2nd-highest-number-of-rabbit-fever-cases-since-1983/
  6. http://www.cdc.gov/Tularemia/
  7. http://www.cdc.gov/tularemia/signssymptoms/index.html
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