The Nature of Viruses - Are Viruses Alive?

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Are viruses alive?

Anyone with a cold or the flu virus feels as if they are under attack by some organism. But in the scientific community it's still an open-ended question. This is why viruses do not belong to a kingdom of living things. Just because a virus seems alive doesn't mean it is alive. After all, it's not even a single-celled organism.

A virus is little more than a strand of DNA or RNA covered by a protein coating. Viruses are a thousand times smaller than bacteria and come in a wide range of shapes. Some look like weird, tall spiders whereas others look like prickly porcupine-like soccer balls.

One thing is for sure; viruses are very much a part of life on Earth and the human experience. Viruses infect animals, plants, and even bacteria. Humans are in a constant battle with viruses. HIV (the virus that causes AIDS), the Ebola virus, and the West Nile virus continue to make headlines and take millions of lives.

Other maladies, such as colds, the flu, chicken pox, measles, and hepatitis, are more common, but sometimes just as deadly. Symptoms vary depending on which kind of cell is under attack. Cold viruses attack the nose and throat, the rabies virus attacks the brain and nervous system, and the human immunodeficiency virus (HIV) attacks white blood cells in the bloodstream. Viruses can even cause some kinds of cancers and leukemia.

Live and Let Die

To determine whether a virus is alive or not, we could compare the virus' characteristics to what many biologists consider the requirements of life. All living things have several common characteristics. Some nonliving things may have one or more of the characteristics, but not all of them. For a virus then to be classified as alive it must:

- Reproduce
- Obtain and use energy
- Grow, develop, and die
- Respond to the environment

Viruses do have DNA or RNA, and DNA is the code for life. Having genetic material is an important step towards being classified as alive. DNA controls the evolution of the cell and the organism. Like living things, viruses evolve through time and thus can adapt to their environment. But unlike cells, viruses cannot use their genetic material by themselves. They need a living cell in order to function and reproduce; otherwise they are playing dead.

Resistance Is Futile

Because viruses are not cells, they can't divide by binary fission like bacteria. Yet they do reproduce themselves in an extraordinary way. Their structure enables viruses to attack a plant or animal cell called a "host cell". The protein shell protecting the virus's DNA is covered with spike-like protrusions. These spikes allow the virus to latch onto ...