It seems like a new virus that's trying to kill us pops up somewhere in the world every other day. While the World Health Organization, the Centers for Disease Control and Prevention, and other health organizations monitor the new coronavirus, officials continue to announce the rapid spread of new COVID-19 infections and deaths around the world.
Despite modern sanitary practices, prevention strategies, and vaccines, there is much to fear from tiny imperialistic pathogens—invisible to all but the most powerful microscopes—that invade our cells to replicate, messing them up like a coke-fueled rock band destroys a hotel room after a concert.
All the hand sanitizer, face masks, and toilet paper in the world can’t save us from some of history’s nastiest viruses and the horrifying diseases they cause in humans.
Here are the 12 worst killers, based on the likelihood that a person will die if they are infected with one of them, the sheer numbers of people they have killed, and whether they represent a growing threat.
In 1967, a group of lab workers in Marburg and Frankfurt, Germany, and in Belgrade, Serbia, contracted a new type of hemorrhagic fever from some virus-carrying African green monkeys that had been imported for research and development of polio vaccines. Spread through close human-to-human contact, symptoms start with a headache, fever, and a rash on the torso, and progress to multiple organ failure and massive internal bleeding.
The mortality rate in the first outbreak was 25%, but it was more than 80% in the 1998-2000 outbreak in the Democratic Republic of Congo, as well as in the 2005 outbreak in Angola, according to the World Health Organization (WHO).
Its melodic moniker may roll off the tongue, but if you contract the virus, that's not the only thing that will roll out of your body: you will probably have a disturbing amount of blood coming out of your gums, for instance. Four of the five known Ebola viral strains cause Ebola virus disease (EVD), which has killed thousands of people in sub-Saharan African nations since its discovery in 1976.
One strain, Ebola Reston, doesn't even make people sick. But for the Bundibugyo strain, the fatality rate is up to 50%, and it is up to 71% for the Sudan strain, according to WHO. The outbreak underway in West Africa began in early 2014, and is the largest and most complex outbreak of the disease to date, according to WHO.
Rabies has a long and storied history dating back to 2300 BCE in records of Babylonians who went mad and died after being bitten by dogs. While this virus itself is a beast, the sickness it causes is now is wholly preventable if treated immediately with a series of vaccinations (sometimes delivered with a terrifyingly huge needle in the abdomen). We have vaccine inventor Louis Pasteur to thank for that.
"It destroys the brain, it's a really, really bad disease," Muhlberger said. "We have a vaccine against rabies, and we have antibodies that work against rabies, so if someone gets bitten by a rabid animal we can treat this person," she said.
However, she said, "if you don't get treatment, there's a 100% possibility you will die."
Human immunodeficiency virus (HIV) causes a spectrum of conditions in those infected, leading to acquired immune deficiency syndrome (AIDS). Cynthia Goldsmith, Centers for Disease Control and Prevention) In the modern world, the deadliest virus of all may be HIV. "It is still the one that is the biggest killer," said Dr. Amesh Adalja, an infectious disease physician and spokesman for the Infectious Disease Society of America.
An estimated 32 million people have died from HIV since the disease was first recognized in the early 1980s. "The infectious disease that takes the biggest toll on mankind right now is HIV," Adalja said.
Powerful antiviral drugs have made it possible for people to live for years with HIV. But the disease continues to devastate many low- and middle-income countries, where 95% of new HIV infections occur. Nearly 1 in every 25 adults within the WHO African region is HIV-positive, accounting for more than two-thirds of the people living with HIV worldwide.
The virus that causes smallpox wiped out hundreds of millions of people worldwide over thousands of years. We can’t even blame it on animals either, as the virus is only carried by and contagious for humans. There are several different types of smallpox disease that result from an infection, ranging from mild to fatal, but it is generally marked by a fever, rash, and blistering, oozing pustules that develop on the skin. Fortunately, smallpox was declared eradicated in 1979, as the result of successful worldwide implementation of a vaccine.
Mortality rates were far higher in populations outside of Europe, where people had little contact with the virus before visitors brought it to their regions. For example, historians estimate 90% of the native population of the Americas died from smallpox introduced by European explorers. In the 20th century alone, smallpox killed 300 million people.
"It was something that had a huge burden on the planet, not just death but also blindness, and that's what spurred the campaign to eradicate from the Earth," Adalja said.
There are many strains of hantavirus floating around (yep, it’s airborne). Different strains, carried by different rodent species, are known to cause different types of illnesses in humans, most notably hemorrhagic fever with renal syndrome (HFRS)—discovered during the Korean War—and hantavirus pulmonary syndrome (HPS), which emerged with a 1993 outbreak in the southwestern United States. More than 600 people in the U.S. have now contracted HPS, and 36% have died from the disease, according to the Centers for Disease Control and Prevention.
The virus is not transmitted from one person to another, rather, people contract the disease from exposure to the droppings of infected mice.
Previously, a different hantavirus caused an outbreak in the early 1950s, during the Korean War, according to a 2010 paper in the journal Clinical Microbiology Reviews. More than 3,000 troops became infected, and about 12% of them died.
This digitally-colorized image shows the H1N1 influenza virus under a transmission electron microscope. No virus can claim credit for more worldwide pandemics and outbreaks than influenza. The Spanish flu in 1918 is generally considered to be one of the worst pandemics in human history, In 2009, this virus (then called the swine flu) caused a pandemic, and is thought to have killed 200,00 people worldwide.
During a typical flu season, up to 500,000 people worldwide will die from the illness, according to WHO.
The most deadly flu pandemic, sometimes called the Spanish flu, began in 1918 and sickened up to 40% of the world's population, killing an estimated 50 million people.
The leading cause of death in the tropics and subtropics is the infection brought on by the dengue virus, which causes a high fever, severe headache, and, in the worst cases, hemorrhaging. The good news is that it's treatable and not contagious. The bad news is there's no vaccine, and you can get it easily from the bite of an infected mosquito—which puts about 3 billion people at risk.
Dengue sickens 50 to 100 million people a year, according to WHO. Although the mortality rate for dengue fever is lower than some other viruses, at 2.5%, the virus can cause an Ebola-like disease called dengue hemorrhagic fever, and that condition has a mortality rate of 20% if left untreated. "We really need to think more about dengue virus because it is a real threat to us," Muhlberger said.
Two vaccines are now available to protect children from rotavirus, the leading cause of severe diarrheal illness among babies and young children. The virus can spread rapidly, through what researchers call the fecal-oral route.
Although children in the developed world rarely die from rotavirus infection, the disease is a killer in the developing world, where rehydration treatments are not widely available.
The WHO estimates that worldwide, 453,000 children younger than age 5 died from rotavirus infection in 2008. But countries that have introduced the vaccine have reported sharp declines in rotavirus hospitalizations and deaths.
Severe acute respiratory syndrome (SARS) caused Asia and Canada to fall into chaos between 2002-2003. Caused by the highly infectious coronavirus SARS-CoV, the disease quickly spread to 37 countries around the world, infecting more than 8000 peolple and killing more than 700 over the course of two years.
The disease causes fever, chills and body aches, and often progresses to pneumonia, a severe condition in which the lungs become inflamed and fill with pus. SARS has an estimated mortality rate of 9.6%, and as of yet, has no approved treatment or vaccine. However, no new cases of SARS have been reported since the early 2000s, according to the CDC.