Ultimately, while no one truly knows what the total toll the Ebola outbreak will have, we do know that the disease has claimed fewer than 5,500 people in history. Despite this comparatively small number, over the decades, it has spawned books (like The Hot Zone) and movies (like Outbreak) and captured the morbid curiosity of the general public.
But what about the truly contagious diseases of the world? To get a sense of where Ebola ranks on a global scale, take a look at some of the deadliest contagious diseases by total death toll around the world.
HIV/AIDS
Even though HIV takes a tremendous toll each year, claiming about 1.6 million lives, the number of people currently living with the disease is more than 35 million. And while those diagnosed with HIV in the initial stages of the epidemic had a life expectancy of months to a few years, since antiretroviral therapy (ART) became available in the mid-1990s, the life expectancy for someone infected with HIV has increased significantly. In fact, someone who is promptly diagnosed with HIV today, who seeks and continues treatment, can live close to a normal lifespan. However, therapy is expensive and out of reach for many of those at risk for contracting the disease – including those living in poverty, in the United States and abroad.
There is still no cure for HIV, which can be spread through unprotected sexual contact, IV drug use, contaminated blood transfusions, and from mother to child.
Tuberculosis
This deadly virus was the inspiration for Edgar Allan Poe’s The Masque of the Red Death and countless other tales because of its deadly nature. But there is good news -- advancements in treatment options mean that 7.3 million people developed TB and survived in 2012. However, more than 1.3 million people have died from tuberculosis.
Recovery from this disease requires a regimen of several drugs over a period of six to nine months. Patients who neglect to follow their drug schedule can develop a drug-resistant form of TB, which is also airborne. For patients who develop this more serious form of the illness, treatment can then extend for up to two years.
Pneumonia
Pneumonia is the world’s leading killer of children -- particularly young children -- taking more lives than AIDS, malaria and tuberculosis combined, according to the World Health Organization (WHO). More than 1.1 million children younger than 5 years old die each year from this disease, caused by pneumococcal bacteria. Risks for this disease are particularly high for the elderly and those with underlying health conditions or compromised immune systems.
While pneumonia can be treated easily in healthy adults, those in high-risk categories face a number of complications, including respiratory failure, sepsis, acute respiratory distress syndrome (ARDS), and less commonly, lung abscesses, where pockets or pus form inside or around the lung. These pockets sometimes need to be surgically drained.
Ringworm
Dermatophytosis, or more commonly, ringworm, is a condition brought on by a fungal infection of the skin. Because of its name, it is often inaccurately believed to be caused by a breed of parasitic worm, when, in fact, this disease is the result of several species of fungi. This fungal infection causes lesions that are round, slightly red, and bordered by scales, blisters or bumps. These lesions are itchy and uncomfortable, although life-threatening cases are extremely rare.
Although this disease is certainly not deadly when cared for properly, its ability to spread from person to person is nearly unrivaled. To contaminate another person, one must only come into contact with infected skin, rather than internal organs or cells.
Giardiasis
Also known as “beaver fever,” Giardiasis is a parasitic infection caused by the ingestion or exposure to infected bodies of water. This condition is one of the most common waterborne diseases in America -- about 2 percent of adults and 8 percent of children in the United States and other developed countries have had a giardia infection. It is believed to be zoonotic -- meaning that animals (mainly beavers) may be responsible for spreading the infection in lakes, rivers and reservoirs.
Infected people develop symptoms such as diarrhea, abdominal cramps, pale or greasy stools, fatigue, bloating, and weight loss. With treatment, this condition can be eliminated with medications in less than 25 days. Left untreated, this condition can cause severe dehydration, which can lead to shock, coma or death.
Malaria
About 200 million cases of malaria are reported worldwide each year, causing about 627,000 deaths. According to the WHO, most deaths occur among children living in Africa, where a child dies every minute from malaria. Malaria is a mosquito-borne disease that can infect human beings efficiently and without warning. This disease is characterized by severe fever and headaches and can lead to coma or death without treatment. The disease is caused by Plasmodium parasites that are most common in tropical and subtropical climates.
Both malaria and TB are becoming a concern for health officials because these diseases are becoming more and more drug resistant throughout the world.
Measles
Measles is a respiratory virus in the same category as influenza. It gets into the lungs and replicates on their linings, called epithelia. This disease then gets into the immune system and sets up shop in the trachea, or windpipe, making it the most contagious disease on the list. Because of its location, this virus has perfected the ability to be aerosolized during a cough or sneeze. A single sneeze or cough will hurtle the measles virus through the air in enormous quantities and can linger on surfaces for two hours.
According to the CDC, measles is so contagious that if one person has it, 90 percent of the people in proximity to that person who are not immune to the disease will become infected. In 2013, measles claimed 145,700 lives worldwide. But according to the WHO, measles vaccination prevented an estimated 15.6 million deaths between 2000 and 2013, making it one of the easiest diseases to avoid.