I think to answer that question, we need to understand what a virus is: A microscopic, infective agent made up of genetic material which is able to multiply only inside the living cells of a host.
Think of a computer virus -- a piece of code or small software program that is designed to “infect” a host computer by embedding and replicating itself within the hard drive to disrupt functionality.
There are thousands upon thousands of unique viruses documented around the world, with new ones being discovered all the time. But they somehow continue to come as a surprise to most people because it wasn’t until the 20th century that we actually started to understand these viruses and come up with solutions to control them.
Many scientists believe that viruses have been around since the first forms of life. And certainly, they all know that the vast majority of viruses do not cause any harm to humans, and actually help maintain the delicate balance of our ecosystem.
So why do certain viruses become deadly to humans?
I would argue that this has to do with the way humans interact in nature. Sometimes, humanity creates a biological mismatch in which the virus goes from its natural host to a place where it doesn’t belong. Some newer species of viruses could be the byproducts of all the biological traffic humanity has created.
From the beginning of time, natural human interaction with nature and with each other has caused people to contract viruses. If you look at the basic necessities for life – food and water – these are two of the most common ways infective agents enter our bodies. Even the Bible makes reference to potential viral outbreaks. In 2 Chronicles 21:15, a letter from Elijah the prophet to Jehoram says “You yourself will be very ill with a lingering disease of the bowels, until the disease causes your bowels to come out.” It sounds similar to some form of rotavirus – which according to the World Health Organization (WHO) – is responsible for more than 500,000 deaths each year as a result of severe dehydration.
Throughout the years, especially in the 20th century, we have seen the devastation caused by viruses like measles, polio and the Spanish flu, which killed over 20 million people. Many of these viruses came about because of the rapid growth of cities, increased access to travel and the basic knowledge of viral transmission. Thankfully though, as these viral threats grew, so did the body of knowledge on how they work and how to control them. Scientists began creating vaccines that are still saving lives today.
However, for each deadly virus we learn to control, there are others that still pose a very real threat.
Ebola: The Ebola epidemic in West Africa is the largest on record and has killed more than 11,200 people. Symptoms of Ebola may appear anywhere from 2 to 21 days after exposure and can include headache, nausea, vomiting, diarrhea, high fever, weakness and joint pain. The virus has no vaccine and no specific treatment, and according to the WHO, a fatality rate of up to 90 percent.
Anthrax: Although not a virus, symptoms can take anywhere from one day to 2 months to appear and vary based on the kind of infection, but often resemble those of influenza. Anthrax is capable of infecting the skin by entering through a cut; the respiratory system through inhalation; the gastrointestinal tract by eating undercooked meat from an infected animal; and the blood stream through injection with the bacterium. The good news is, the only way to contract the illness is to come in direct contact with anthrax spores – not by coming in contact with an infected person. Some anthrax infections can be treated with a 60-day course of antibiotics, but inhalation anthrax infections sometimes produce more toxins than drugs can handle.
Marburg virus: First identified during outbreaks in Marburg and Frankfurt, Germany in 1967, this virus came from the import of infected monkeys from Uganda. It is a severe and highly fatal disease caused by a virus from the same family as the one that causes Ebola. The symptoms of Marburg virus come on quickly and include severe headache and fatigue. It’s transmitted by direct contact with blood, tissue or bodily fluids from an infected person or animal, and there is currently no treatment for the disease.
Hantavirus: People become infected with hantavirus through contact with the feces, saliva or urine of infected rodents or by inhalation of the virus from rodent excrement. Hantavirus originated in Asia, but different forms of the virus have emerged in other countries including the United States and Canada. While cases of human infection with hantaviruses are relatively rare, they can be fatal. Hantavirus Pulmonary Syndrome, which is caused by inhalation of the virus from rodent droppings, has early symptoms that include fatigue, fever and muscle aches, especially in the large muscle groups. Later on, a patient may suffer from coughing, shortness of breath and chest tightness as the lungs fill with fluid. There is currently no cure for hantavirus infections, but victims who receive early treatment in intensive care units tend to have a better survival rate.
HIV: We all know this one. Human immunodeficiency virus (HIV) affects 35 million people worldwide and while great strides have been made in developing treatments to extend the life of patients, the sad reality is: There’s still no cure and we’re nowhere near controlling the epidemic.
Now, one might argue that hepatitis B or influenza kill more people each year than the viruses I’ve identified, but remember, these are viruses that have vaccines available to help prevent and control them.
Sadly, today we are dealing with a world that is simply out of control. Whole countries are being destroyed by radical militants, medical services are being eradicated in various nations whose infrastructures have been devastated, and in some developing countries, the tools needed for basic hygiene — like clean water — just don’t exist.
The bottom line is: We can’t start the 21st century going backwards. Many deadly viruses still exist in the world around us that destructive human behavior could unleash. If we keep heading in this direction, Ebola will not be the only outbreak we have to worry about.
Dr. Manny Alvarez serves as FOX News Channel's (FNC) Senior Managing Editor for Health News. Prior to this position, Alvarez was a FNC medical contributor.