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Your Good Health: What's the difference between viral, bacterial infections?

There are vaccines for many bacterial and viral diseases. Vaccines “teach” the body what to look out for so that an infection can be responded to more quickly.
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Dr. Keith Roach

Dear Dr. Roach: I watched a show that described how a virus invades a cell and found it fascinating. What is the difference between a viral and a bacterial infection?

G.D.

Viral infections start by using a cell receptor to gain entry into the cell. This receptor depends on the virus; for example, SARS-CoV-2 (the virus that causes COVID) uses the ACE2 receptor to get into the cell, while HIV uses a different receptor called CD4.

Once the virus is in the cell, it inserts its own genetic material into the cellular machinery, causing the cell to make a virus rather than do the job it’s supposed to do until it ultimately dies. Viruses cannot replicate by themselves; they need a host to do so. The viral infection may kill its host if it destroys enough of the host cells.

The body can get rid of the virus by recognizing and killing its own cells that have been taken over by the virus. (That’s the job of the cytotoxic T cells.) It also neutralizes the virus through antibodies (the job of the B cells, helped out by T cells). Sometimes a balance is reached, and a chronic viral infection ensues. Doctors use antiviral drugs to help with viral infections.

A bacterial infection, by contrast, uses the host body as a source of nutrients. Because bacterial cells grow so fast, they outcompete the host cells for sugar, oxygen and other critical nutrients. The bacteria can kill the host by using up resources and can also make toxic substances that damage the body. The body has granulocytes, macrophages and antibody-making B cells to help fight bacteria. Although there are chronic bacterial infections, usually one side or the other ends up “winning.”

Doctors help the body fight bacterial infections with antibiotics. The body’s robust inflammatory response, although necessary, sometimes causes as much or even more trouble than the infection, and one way we can help the body is by toning down its response to some critical infections.

There are vaccines for many bacterial and viral diseases. The vaccines “teach” the body what to look out for so that an infection can be responded to much more quickly by the full array of the body’s defenses.

Dear Dr. Roach: Is it safe to take a sleep aid in the evening? I normally do not have a problem falling asleep, but I often wake up in the middle of the night and can’t get back to sleep. So, at times, I take half of a gummy containing melatonin and chamomile, and I’m able to get a few more hours of sleep. Is this safe?

While it’s best not to take sleep medicines at all (cognitive behavioral therapy remains the most effective and least dangerous treatment, although it isn’t accessible to everyone), chamomile and melatonin are pretty safe. It certainly doesn’t work for everyone, but if it is working for you, it’s not a bad option.

During very stressful periods of my life (like medical school), chamomile tea did help me fall asleep, and it is safe, except that it can occasionally interfere with some medications, including anti-seizure medicines and sedatives.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu