Most Deadliest Communicable Diseases

My List of the Five Deadliest Communicable Diseases

I was reading a very interesting article entitled "The Five Deadliest Diseases in History" where the author looked at the deadliest diseases in history in terms of number of deaths over time.

I wanted to do something similar but from a different angle. My list includes 5 diseases that are always or nearly always fatal.

Some of these diseases are quite rare, some are well known. Some have no treatment options available and some have antibiotic, vaccination or other treatment, however death is a sure thing without appropriate and timely treatment.

The dictionary definition of case-fatality rate is the proportion of individuals contracting a disease who die of that disease. The following communicable diseases have a case-fatality rate of one hundred or nearly 100 percent.

Prion Disease

The prion diseases or transmissible spongiform encephalopathies (TSE) are characterized by progressive, deterioration of the brain. The human prion diseases are always fatal.

The TSE's include Creutzfeldt-Jakob disease and all its variants, kuru and Gerstmann-Staussler-Scheinker syndrome.

Though not fully characterized, a prion is an abnormally folded protein which can have long incubation times of many years.

Human prion disease can be acquired through diet, medical treatment, surgery or blood transfusion and some are considered genetic. There is no treatment for human prion disease.

Naegleria fowleri

Infection with this free-living amoeba known as primary amoebic meningoencephalitis (PAM) is nearly 100 percent fatal even with treatment.

The amoeba invades the brain through the nose while people partake in recreational water activities in warm, fresh water. The amoeba finds its way to the brain when water rushes up the nose and destroys the tissue of the brain.

Symptoms of this very rare disease include severe frontal headache, hallucinations, fever and death occurs within 10 days.

Untreated Rabies

This viral disease that people get through the bite of an infected animal is nearly 100% fatal in the absence of timely vaccination and rabies immunoglobulin.

Headache, fever, hydrophobia, delirium and occasionally convulsions are the symptoms seen before coma and death occurs.

Rabies is not a rare disease and 55,000 people die this horrible death worldwide mostly in developing countries because of inadequate or no post-exposure treatment.

Untreated Septicemic and Pneumonic Plague

While untreated bubonic plague has a case fatality rate of up to 60%, untreated septicemic and pneumonic plague are invariably fatal.

Plague is caused by infection with the bacterium, Yersinia pestis. People typically get this disease from the bite of a plague-infected flea. With timely and appropriate antibiotic treatment, all forms of plague can be countered.

Untreated African Sleeping Sickness

This disease which is restricted to certain areas of Africa is fatal without appropriate treatment. This parasitic disease from the Trypanosoma species is transmitted to people through the bite of the tse tse fly.

This disease starts out with fever, headache and joint pain later to invade the central nervous system. 

At this point confusion and a disturbed sleep cycle kicks in and without treatment, coma and death will ensue.

The following communicable diseases get honorable mention as being close to having a 100 percent case-fatality rate:

Up to 90% case-fatality: Ebola virus 

Up to 85% case-fatality: untreated inhalation anthrax 

Up to 80% case-fatality: Marburg virus 

Over 70% case fatality: Herpes B virus