Unlike bacteria, a virus is not a complete organism and cannot survive on its own. “It needs a host and then it acts like a serial killer,” Dr. Pawan Grover says. It can use the host’s DNA make, which increases the risk of mutation. This is what makes viruses difficult to contain, he adds.
Some are more lethal than others if the factors are right, Dr. Brent W. Laartz, a board certified infectious diseases specialist, says. Viruses must invade cells of a living host to reproduce and if a person has no immunity, the result can be deadly.
Viruses spread through contact, mostly with contaminated food and water. Natural and manmade disasters are some of the biggest causes of outbreaks. This is when people are most vulnerable because health care systems and distribution are compromised.
Flu-like viruses – such as Bird flu, Ebola and Marbug – can cause hemorrhagic fever. “This is when the disease can get deadly,” Dr. Grover says. The infectious disease interferes with the blood's ability to clot. Such illnesses usually affect health care workers first, he adds. “This is because when someone sick gets to the ER no one has a clue yet what the illness could be.”
Unfortunately, viruses never really go away. “They have always been in existence even before we were alive as species,” Dr. Grover says. Some are better known because of the media attention they get. But not hearing about them doesn’t mean they have been eradicated.
Many deadly viruses can be treated if caught early enough, but some have an intermission period of up to a year. Considering that most of the symptoms are similar to the seasonal flu – fever, exhaustion, muscle aches – it’s easier to misdiagnose an infection, Dr. Laartz says. A few exceptions are measles and smallpox because rashes should start soon.