MadSci Network: Immunology

Re: How often can bacterial infections be overcome by the immune system?

Date: Wed Aug 1 16:17:36 2001
Posted By: Doug Reed, Faculty, Toxinology & Aerobiology, USAMRIID
Area of science: Immunology
ID: 993438077.Im

Well, I hate to put it this way but I think your observation is tainted by 
what you perceive as common bacterial and viral infections. A 
normal, healthy immune system overcomes bacterial infections all the time. 
The common cold, caused by rhinoviruses, is typically 
resolved quickly. Most people who think they have the flu really have a 
rhinovirus infection and not influenza. Influenza symptoms, in contrast, 
typically last 
two weeks and are typically far more severe than common cold symptoms. 
Hepatitis viruses, Herpes viruses (including chicken pox), HIV, Human 
papilloma virus, and many other viruses are examples of viral infections 
that can last years; for most of those viruses the infection is never 
resolved and the virus is always present. It may go latent at times but it 
remains in your body, ready to re-emerge at a later time.

I can think of a number of common bacterial infections which can resolve 
themselves without treatment: Salmonella, Listeria, E. coli, Strep, Staph. 
Yes, all of these bacteria can be lethal (so can influenza!). But many 
people every year get infections from eating contaminated food and they do 
not succumb to the bacteria even without antibiotics. Staph can infect 
wounds and can be resolved with a little neosporin or betadine. Strep 
throat is commonly treated with antibiotic but not because you can't get 
rid of it yourself - the immune response to strep can result in rheumatic fever 
and damage to the heart, so the antibiotic gets rid of the bacteria before 
the immune system gets going. The concern with antibiotic resistant 
bacteria is not with normal healthy people but with hospital patients, 
many of whom are ill and immunosuppressed and cannot fight off infections 
that healthy people could fight off easily.

Antibody is not less effective for attacking bacteria, in fact it really 
functions best against bacteria and not against viruses which can hide 
inside cells. This is why antibody is so ineffective against HIV and why 
an HIV vaccine has been so difficult to generate.

To sum up, you can look at the variety of bacteria and viruses that infect 
humans and find a wide variety of symptoms and resolutions. I don't think 
that the immune system is any better (or worse) in general terms of 
fighting bacteria versus viruses - I think it is far more dependent upon 
the individual bacteria or virus. One could make a case, though, for the 
immune system being poorly equipped to handle parasites - amoeba, worms, 

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