#IDFridays Week 51: The Plague

Name
Plague aka The Black Death

Transmission

An infectious disease caused by a bacteria called Yersinia Pestis
These bacteria mostly live in small mammals (especially wild rodents)
The bacteria spread among rodents through fleas (insects) that bite infected rodents and then bite a healthy rodent
There are 3 main forms of the plague depending on how it infects a person:
- Bubonic: the most common form which is caused by an infected flea bite. The bacteria enter the body through the flea bite and multiply in the lymph node closest to bite. They can then spread to other parts of the body. This form cannot spread from one human to another.
- Septicemic: when the infection spreads through the bloodstream (can happen from flea bites or direct contact with infected mammals or infected materials through cracks in the skin)
- Pneumonic: the least common form is lung-based plague which is also the most deadly (untreated, the death rate is close to 100%). It’s usually caused by an advanced case of bubonic or septicemic plague where the bacteria spread to the lungs. This form can spread from person to person through contaminated droplets in the air (coughing, sneezing, etc.)

Geography
Worldwide (the bacteria can be found all over the world, especially in the tropics/subtropics and warmer areas of temperate countries)

Incubation Period
3 – 7 days

Signs and Symptoms
General symptoms mimic the flu:

Symptoms specific to the form of the disease are:

Bubonic
- Lymph nodes that are swollen, tender, or painful (called buboes)
Septicemic
- Abdominal pain
- Shock
- Bleeding under the skin and other organs
- Black skin/tissue (especially fingers, toes, and nose)
Pneumonic
- Pneumonia
- Bloody or watery mucus
- Shortness of breath
- Chest pain
- Cough

Diagnosis
Laboratory testing of blood, sputum (mucus from the throat), or fluid from buboes

Treatment

Treatment involves the use of supportive therapy and antibiotics such as streptomycin and tetracycline
People with the pneumonic form have to be quarantined and healthworkers must use personal protective equipment (PPE)

Prognosis

Early diagnosis and treatment are important for survival
- Without treatment, death rates can be 60% or higher
- With treatment, death rates are less than 15%
Available vaccines are not very effective against pneumonic plague

Prevention: What Can You Do?

Reduce the chance of rodents living in your environment
- Seal and store food in rodent-proof containers
- Dispose of garbage far from your home
- Keep your home clean and exterminate if you have a rodent problem
Use insect repellent and take precautions against flea bites
Do not handle dead animals especially dead rodents or other small animals

Plague In the News