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Is It a Virus or a Bacterium? Know the Difference

In general, most colds and other respiratory infections are not serious for adults in good health. It's just the hassle of dealing with runny noses, coughing, sneezing, fever, headaches, aching muscles, and fitful sleeping. But knowing whether your infection is caused by a virus or a bacterium makes a difference in how it is treated.

Which is it?

Bacteria are one-celled organisms that multiply by simple division. They are linked to such respiratory infections as otitis media (ear), tonsillitis (tonsils), pneumonia (lungs), bronchitis (airways), sinusitis (sinuses), pharyngitis (throat), and whooping cough (airways).

Most respiratory infections, however, are caused by viruses rather than by bacteria. Viruses are some of the tiniest entities known.

Unlike bacteria, they do not divide and do not reproduce on their own. Instead, when they invade a cell, they take over the cell’s machinery, forcing the cell to reproduce the virus in massive numbers. Viruses infect animals, plants, and bacteria, and cannot be wiped out by antibiotics. Viral reproduction, on the other hand, can be blocked by antiviral agents.

Viruses cause such respiratory infections as the common cold (rhinovirus), the flu (influenza), some pneumonias and bronchiolitis (respiratory syncytial virus, or RSV).

It can be difficult to determine whether you have a viral or bacterial infection because the symptoms are often similar. A doctor will most likely have to conduct tests. But here are a few hints.

If you have a cold or cough, it is usually viral. You should suspect a secondary infection caused by bacteria if a fever recurs after the first few days. A persistent earache may mean a bacteria-based ear infection. With a sore throat, it takes a throat culture to determine if it is bacterial. The only common bacterial throat pathogen is streptococcus. The majority of sore throats, especially in adolescents and adults, are viral.

Treatment and prevention

Viral infections may temporarily decrease your resistance and may be followed by a secondary bacterial infection, so it is important to call your doctor if you get a respiratory infection and you have diabetes or another chronic illness that weakens your immune system.

Most viruses remain alive for a period of time in airborne particles that people breathe, sneeze, and cough, as well as on surfaces for about an hour after they are touched by an infected person. That is why it is important to wash your hands regularly and immediately after handling potentially viral-contaminated objects such as doorknobs, shopping carts, telephones, toys, and other commonly shared items.

In addition: Don't smoke. It weakens the immune system and makes the respiratory system more vulnerable to infection.

Because many viral infections do not produce symptoms immediately, you or someone you're in contact with may be contagious for several days before you know it. This makes prevention difficult.