Just in case you haven’t had enough fright during this Halloween season, here’s a rundown of some of the most terrifying diseases out there. Many are quite rare and a couple are fairly common, but it’s worth familiarizing yourself with all of them to stay at your healthy best.

1. Ebola

This horrifying disease, easily spread through infected bodily fluids, made headlines last year when an outbreak in Africa led to a handful of cases in the U.S. It’s not currently a threat on our shores, but it could happen again if we’re not vigilant.

Ebola is a hemorrhagic disease that’s fatal more than half of the time in Africa, even with treatment. Late-stage symptoms include bleeding from the mouth, eyes, ears, nose, and rectum. Organ failure also may result. Earlier symptoms include fever, nausea, vomiting, and weakness. There is no known cure, although some experimental drugs seem to have been effective for a few patients. Typically, patients are given fluids and blood to replenish their systems; many of those who survive suffer long-term or permanent complications.

2. Brain-Eating Amoeba

Naegleria fowleri is an example of the several kinds of freshwater amoeba that can literally destroy your brain. It’s a microscopic organism found mostly in the southern U.S. in freshwater, such as lakes and hot springs, and soil. As horrible as it sounds–and is—it is exceedingly rare (only 35 cases were reported from 2005 to 2014).

With this scary disease, the amoeba travels up the nose and into the brain, where it results in primary amebic meningoencephalitis, an infection causing headache, stiff neck, fever, and hallucinations. It’s almost invariably fatal within days. One possible way to prevent it: Wear nose plugs when swimming in freshwater lakes, rivers, and streams.

3. Flesh-Eating Bacteria

Also known by its medical name, necrotizing fasciitis, this condition occurs when bacteria enter the body through a wound or cut and spread rapidly. The infection creates toxins that destroy tissue, causing extreme pain, swelling and discoloration. If not treated immediately with powerful antibiotics, patients can lose limbs and even die.

Estimates on the prevalence of necrotizing fasciitis vary. According to the Centers for Disease Control, about 650 to 850 people each year contract the disease because of Group A Streptococcus bacteria, the most common bacteria—but not the only one—responsible. Healthy people generally can fight off invasive bacteria, but if your immune system is compromised in any way, it’s especially important to thoroughly cleanse wounds and open cuts.

4. Locked-In Syndrome

People with locked-in syndrome, or pseudocoma, are completely conscious but unable to move or make a sound. This terrifying condition happens to a small percentage of people after a stroke, blood clot, infection, tumor, or trauma. It can also be seen in people with amyotrophic lateral sclerosis (ALS). It’s usually possible for those with locked-in syndrome to communicate via eye movements or blinking. Depending on the cause of the syndrome, partial or full recovery may be possible with time.

5. Influenza

We’re not accustomed to thinking of the flu as a scary disease, but it killed upwards of 21 million Americans during the pandemic of 1918-1919. Even today, the flu causes thousands of deaths per year. For most people who get it, though, the fever, cough, fatigue, body aches, and sore throat will run their course in time. And while it’s not a guarantee, the annual flu vaccine provides significant protection against the illness.

6. Pneumonia

Like influenza, this disease is not normally thought of as the killer it used to be in pre-antibiotic times. Pneumonia is, however, still a leading cause of death in the U.S. and disproportionately affects older people or those who have underlying conditions. Caused by viruses, bacteria, fungi, protozoa, and other organisms that infiltrate the lung (or lungs) and make the alveoli (air sacs) swell, pneumonia sufferers experience coughing, heavy mucus production, shortness of breath, and fever. Getting a flu shot can go a long way toward preventing the condition, as influenza is a common cause of pneumonia. Your doctor also may recommend vaccines that prevent certain streptococcus infections, whooping cough, and measles, all of which can lead to pneumonia.

7. Rabies

That raccoon or skunk you see outside acting strangely? That bat in your attic? Don’t tangle with them. If you get bitten by an animal that has the rabies virus, you could contract the illness. A series of rabies vaccines administered shortly after exposure will prevent rabies from developing, along with proper wound cleaning with an anti-rabies antibody. However, if you don’t seek treatment, rabies is almost invariably fatal, with delirium, agitation, and hallucinations as its late-stage hallmark.

Aileen Marty, MD, reviewed this story on October 9, 2015.


Marty, Aileen, MD. Email conversation with source on October 3 2015.

“Learn about pneumonia.” American Lung Association. Accessed on October 1, 2015.

“Naegleria fowleri — primary amebic meningoencephalitis (PAM) — amebic encephalitis.” Centers for Disease Control and Prevention. Accessed on October 7, 2015.

”The great pandemic.” United States Department of Health and Human Services. Accessed on October 7, 2015.

”Necrotizing fasciitis: a rare disease, especially for the healthy.” Centers for Disease Control and Prevention. Accessed on October 6, 2015.

“Ebola virus disease.” MedlinePlus. Accessed on October 5, 2015.

Laureys S, F Pellas, P Van Eeckhout, S Ghorbel C Schnakers, et al. “The locked-in syndrome: what is it like to be conscious but paralyzed and voiceless?” Progress in Brain Research. [2005]150:495-511. Accessed on October 6, 2015.

”Locked in syndrome.” National Organization for Rare Disorders. Accessed on October 7, 2015.

”Estimating seasonal influenza-associated deaths in the United States: CDC study confirms variability of flu.” Centers for Disease Control and Prevention. Accessed on October 6, 2015.

”What are the signs and symptoms of rabies?” Centers for Disease Control and Prevention. Accessed on October 7, 2015.