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Microbes Can Cause Different Kinds of Infections

photo of a man with shingles on his neck
Herpes zoster, or shingles, is a painful disease of the nerves that often emerges later in the lives of those who had chickenpox as children. Credit: NIAID.

Some disease-causing microbes can make you very sick quickly and then not bother you again. Some can last for a long time and continue to damage tissues. Others can last forever, but you won’t feel sick anymore, or you will feel sick only once in a while. Most infections caused by microbes fall into three major groups:

  • Acute infections
  • Chronic infections
  • Latent infections

Acute Infections

Acute infections are usually severe and last a short time. They can make you feel very uncomfortable, with signs and symptoms such as tiredness, achiness, coughing, and sneezing. The common cold is such an infection. The signs and symptoms of a cold can last for 2 to 24 days (but usually a week), though it may seem like a lot longer. Once your body’s immune system has successfully fought off one of the many different types of rhinoviruses or other viruses that may have caused your cold, the cold doesn’t come back. If you get another cold, it’s probably because you have been infected with other cold-causing viruses.

Chronic Infections

Chronic infections usually develop from acute infections and can last for days to months to a lifetime. Sometimes people are unaware they are infected but still may be able to transmit the germ to others. For example, hepatitis C, which affects the liver, is a chronic viral infection. In fact, most people who have been infected with the hepatitis C virus don’t know it until they have a blood test that shows antibodies to the virus. Recovery from this infection is rare—about 85 percent of infected people become chronic carriers of the virus. In addition, serious signs of liver damage, like cirrhosis or cancer, may not appear until as long as 20 years after the infection began.

Latent Infections

Latent infections are “hidden” or “silent” and may or may not cause symptoms again after the first acute episode. Some infectious microbes, usually viruses, can “wake up”—become active again but not always causing symptoms—off and on for months or years. When these microbes are active in your body, you can transmit them to other people. Herpes simplex viruses, which cause genital herpes and cold sores, can remain latent in nerve cells for short or long periods of time, or forever.

Chickenpox is another example of a latent infection. Before the chickenpox vaccine became available in the 1990s, most children in the United States got chickenpox. After the first acute episode, usually when children are very young, the Varicella zoster virus goes into hiding in the body. In many people, it emerges many years later when they are older adults and causes a painful disease of the nerves called herpes zoster, or shingles.

Researchers are studying what turns these microbial antics off and on and are looking for ways to finally stop the process.

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Last Updated November 03, 2010