To say that the world is littered with viruses is an understatement. There are an estimated 10 nonillion viruses on the planet — enough of them to assign to every star in the universe 100 million times over. Despite this, humans can cohabitate with these nonillions of viruses relatively disease-free, as most viruses are not able to or interested in jumping into the human body. Those that do, though, can make a person sick. How sick depends on the virus in question, as some viruses are far more dangerous than others. A few are downright deadly.
Which of the nonillions of viruses on this planet wreak the most havoc on the human body? Below is an overview of the most dangerous viruses based on the survival rates, the number of people who have died from them and whether they represent a growing threat.
The Marburg virus first made its debut in 1967, when lab workers in Germany were exposed to infected monkeys that came from Uganda. The virus acts similarly to Ebola in that it causes haemorrhagic fevers, or fevers that are so high they cause bleeding throughout the body. If not brought down in time, the fevers can lead to shock, organ failure and eventual death.
The case mortality rate for Marburg virus varies considerably, at between 23% and 90%. During the first outbreak, the mortality rate was just 25%. However, during subsequent outbreaks — one of which occurred between 1998 and 2000 and another that occurred in 2005 — the mortality rate was much higher, at 80%.
Marburg virus is extremely contagious, making outbreaks particularly dangerous. As of March 2023, Tanzania reported a Marburg outbreak, putting the rest of the African continent at risk of contracting it.
Since the first outbreak in 1976, Ebola has remained a constant threat to global health. Ebola is transmitted through contact with bodily fluids, such as blood or semen, and through the consumption of infected animal tissue by humans.
Not all strains of Ebola are created equal. Some are more dangerous than others, with the most mild of strains unable to make people sick. However, other strains — such as the Bundibugyo and Sudan — have mortality rates of up to 50% and 71%, respectively.
The last outbreak of Ebola virus in West Africa in 2014 is the most complex and largest outbreak of the virus to date. Though there are no current outbreaks of Ebola in Africa, the risk is ever present.
Before the World Health Assembly officially declared the world free of smallpox, it was one of the deadliest viruses with which humans had ever come into contact. In the thousands of years that it tormented people, it killed hundreds of millions, if not billions, of people. In the 20th century alone, smallpox killed an estimated 300 million individuals. Researchers believe that smallpox is responsible for up to 90% of Native American deaths. Those who did survive often lived with permanent scars and blindness.
Though smallpox is no longer around, its implications are far reaching. Not only did it devastate almost entire populations, but it took a huge toll on the productivity of many affected regions, as survivors were often left blind. This fact, combined with the high fatality rates, is the reason for the global campaign to eradicate the disease once and for all.
HIV is perhaps the deadliest virus the modern world has seen. Since the first cases of HIV appeared in the 1980s, more than 36 million people have died from the disease. Fortunately, powerful antiviral drugs had made it possible for infected persons to live for decades longer than they would be able to otherwise. Unfortunately, antiviral medications are expensive and often unavailable in low- to middle-income countries. South Africa is one such country. These regions account for approximately 95% of all new cases. In Sub-Saharan African alone, as many as one in 20 adults lives with the disease.
Without treatment, HIV inevitably turns into the fatal AIDS, also known as Stage 3 HIV. How quickly it transforms into AIDS depends largely on a person’s overall health and lifestyle. That said, it can take anywhere from 2 to 15 years for a person to move into the third stage of an HIV infection. Once a person is in the third stage of infection, his or her life expectancy drops to three years.
In many parts of the world, rabies is nearly non-existent thanks to vaccines for pets and education. However, in under- or undeveloped parts of the world, the virus continues to pose a major threat to humanity. This is particularly true in parts of Africa.
If left untreated, rabies is deadly 100% of the time. It moves quickly, destroying the brain as it goes. Persons who contract the virus and develop symptoms typically die within three to 10 days of the onset of symptoms.
If a person gets bit by an animal that may have rabies, immediate administration of antibodies can protect him or her against the virus. However, it cannot be stressed enough that antibodies must be administered immediately for them to be effective.
Hantavirus pulmonary syndrome is a severe, often fatal, disease that affects the lungs and other parts of the respiratory system. It is a rodent-borne virus that is typically transmitted to humans through infected droplets in the air. These droplets come from fresh rodent urine, faeces or nesting materials. A human becomes infected when he or she breathes in these droplets.
Early symptoms of hantavirus include fever, muscle ache and fatigue. They may also include the chills, dizziness, headaches and abdominal issues. Within four to 10 days of the onset of symptoms, the later stages of the disease begin. In the later stages, infected persons may develop coughing and shortness of breath. This shortness of breath is severe and, as one survivor put it, may make breathing feel like you have a tight band around your chest and a pillow over your face. This feeling continues as the lungs fill more and more with fluid. For as much as 38% of people who contract HPS, the condition is fatal once breathing issues begin.
Hantavirus is not typically found in South Africa but rather, in rural parts of the United States and South America. However, one case was reported in the country in 2021.
Another rodent-borne illness, the Lassa virus — otherwise known as “Lassa fever” or “Lassa haemorrhagic fever” — was first discovered in 1969 by a missionary to Nigeria. Upon contracting the virus, the missionary and her nurse both succumbed to the condition. Since then, approximately 300,000 to 500,000 new cases of the virus crop up every year, many of them in Western African regions. It is responsible for nearly 5,000 deaths annually.
There is no known vaccine for Lassa virus yet. However, scientists believe that people contract it after coming into contact with surfaces or foods infected with urine or faecal matter that contains the virus.
The Lassa virus quickly replicates. As a result, it quickly spreads throughout the body, making it particularly dangerous for humans. Initial symptoms may include fatigue, weakness, sore throat, coughing, headaches, deafness, gastrointestinal distress and haemorrhagic fever. Most people develop these symptoms within one week of exposure. Shortly after initial symptoms begin, infected persons may begin to bleed from the gums, nose and eyes, as well as experience respiratory distress. Neurological issues are also not uncommon.
As the virus spreads, it attacks every tissue throughout the body before progressing to the vascular system. Once there, the virus can be deadly. In fact, as many as 20% of persons who contract the virus die from it, primarily due to multi-organ failure.
Responsible for a whopping 390 million infections worldwide each year, the Dengue virus is an extremely deadly virus. The virus, which contains five strands, is transmitted via the bites of female mosquitos. Though Dengue can occur anywhere, it is primary found in Africa and Asia due to the warm, tropical climates of these regions.
Symptoms of Dengue are severe from the start. Within 14 days of contracting the virus, an infected person may experience bone and muscle pain, splitting headaches, rashes and bleeding gums. In more serious cases, infected persons develop Dengue Haemorrhagic Fever, which is often accompanied by extreme bleeding, leaking plasma, low blood pressure and eventual shock. Though not as common, the disease can cause damage to the brain, heart and liver and trigger inflammation of the brain or organ failure.
The mortality rate of Dengue is relatively low, as between 1% and 5% annually. However, it still kills as many as 25,000 individuals each year, making it a continual global threat.
Rotavirus is the most common cause of upset stomach and diarrhoea in infants and children across the globe. It is so widespread, in fact, that most every child under the age of five will have been afflicted by rotavirus at some point. Also commonly referred to as the “stomach flu,” rotavirus damages the lining of the small intestine, leading the feelings of nausea and the urge to either vomit or defecate.
Rotavirus is primarily transmitted via the faecal-oral route. It is easily preventable through proper sanitation measures and good hygiene. Children tend to lack both these things, which is why rotavirus most commonly occurs in young people.
Initial symptoms of rotavirus are relatively non-concerning, as they include fever and nausea. However, once vomiting and diarrhoea set in, dehydration becomes a major concern. Either can last anywhere from four to eight days, causing an infected person to become severely dehydrated and malnourished.
Because of its prevalence, treatments for rotavirus are widely available. That said, an alarming 215,000 or so children die from the virus each year. Child deaths most frequently occur in regions where treatment is unavailable.
Influenza, more commonly known as the “flu,” is a serious and sometimes deadly respiratory virus that has been affecting humans for millennia. It is extremely contagious and is spread through sneezing, coughing and the touching of infected surfaces.
Symptoms of flu typically begin two days after exposure and include sore throat, runny nose, fever, muscle aches, chills, fatigue, coughing and headaches. Some people develop vomiting and diarrhoea, but not all. These symptoms in and of themselves can become worrisome, but the most troubling aspect of influenza is its tendency to turn into viral pneumonia. Viral pneumonia in and of itself is dangerous, but it is particularly hazardous for young persons, elderly people and individuals with compromised immune systems. This is evident in the fact that, despite widely available vaccines and standard treatment measures, some 375,000 individuals lose their lives to influenza each year. In past centuries, those numbers were much higher, with some outbreaks claiming hundreds of millions of lives worldwide.
There are more viruses in the universe than there are stars but, despite this, very few affect humans. Those that do, though, can wreak havoc on our immune systems and overall health, with some claiming lives more often than not. Given this information, it is in your best interests to take steps to mitigate your risk of contracting viruses, protect your overall health and, possibly, safeguard your life.