Public Release: 

Common Cold Caused By Multiple Viruses

American Society for Microbiology

A recent study investigating causes of the common cold affirms that most colds are caused by viruses, but only half are a result of infection with the rhinovirus, the virus most often implicated in colds. These findings support the recommendations that antibiotics, which do not work on viral infections, not be used to treat cold symptoms. The study appears in the February 1998 issue of the Journal of Clinical Microbiology.

Researchers from the National Public Health Institute of Finland report on a study of 200 cases of the common cold in university students over a one-year period. Student participants were asked to identify when they had a cold, based on a set of symptoms, and contact a study office, set up at the university, within two days of the appearance of the symptoms. The students were then tested to determine the cause of the symptoms.

In 138 of the 200 cases, the researchers were able to identify an infectious agent as the cause. Rhinovirus was found to be the cause of 105, or just over half the cases in the study. Other causes of cold symptoms included coronavirus, influenza A virus, and respiratory syncitial virus (RSV). All of these viruses are known to cause symptoms associated with colds. Nearly all the colds with a known cause were found to be caused by a viral infection. Only 7 patients were found to have bacterial infections, but six were also found to have a viral infection as well.

"These findings are consistent with our recommendations that antibiotics not be used to treat common cold symptoms" says Stuart Levy, president-elect of the American Society for Microbiology. "Almost all cases of the common cold are caused by viruses and antibiotics do not work on viral infections. The unnecessary and inappropriate use of antibiotics to treat cold symptoms is contributing to the development of antibiotic-resistant bacteria.

Despite this research and previous studies showing that antibiotics are of little use in treating the common cold, it is estimated that up to 60% of patients with common colds receive some type of antibiotic. This results in an estimated cost of $37.5 million per year in the United States for unnecessary prescriptions on top of the risk of developing antibiotic resistance.

Mild upper respiratory illness, also known as the common cold, is identified by a set of symptoms. These symptoms can include inflamed sinuses, nasal congestion and a sore throat. Studies done as early as the 1960s have identified rhinovirus as a frequent cause of colds, but the number of cases in which rhinovirus was detected has been as low as 25 percent. Although diagnostic methods have improved greatly since then, no studies into the cause of the common cold have been published recently.

The researchers say that individuals who develop colds do not need to have their doctors test for the cause. The price of diagnosis ($700 per patient in this study) is too high and only in rare cases will it affect treatment.

The Journal of Clinical Microbiology is a publication of the American Society for Microbiology (ASM). With over 40,000 members worldwide, the ASM is the oldest and largest single biological membership organization in the world.


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