The young girl’s mother recalled that upon learning that her daughter’s illness was not caused by influenza, emergency room personnel said, “She does not have the flu. She has a virus. Give her Motrin and Tylenol, and she will be fine.”
There are many viruses that cause flu-like symptoms in children and adults alike – rhinovirus, human metapneumovirus, adenovirus, parainfluenza. Historically, we have paid less attention to these viruses since there were no good methods for detecting them and few antivirals to treat them. Do they matter? They do.
At the height of the 2009 influenza A/H1N1 pandemic, no more than 42.1% of specimens tested by the U.S. Centers for Disease Control tested positive for influenza. The patients behind these specimens obviously had severe enough flu-like symptoms to warrant testing. If no more than 42.1% had influenza, what did the other 57.9% have?
Data from laboratories around the nation has shown that many patients who were suspected of having influenza this past flu season actually had other viruses. In some cases, patients were carrying more than one virus.
Respiratory viruses are widespread and occur year-round — not just in “flu” season. They are, in many cases, indistinguishable from one another based on symptoms alone; and they can lead to significant sickness and death if associated with other co-morbidities.
Rhinovirus, which causes the common cold, comes in many different strains. Once marginalized as a mild infection, it is being recognized as an increasingly important and serious respiratory virus. This past flu season when doctors at Children’s Hospital of Philadelphia saw a quick rise in patients with influenza-like symptoms, they thought the spike was caused by influenza A/H1N1 (2009). Tests revealed that many of the cases were actually caused by rhinovirus.
Research presented at the International Conference on Health-Associated Infections in March 2010 found that patients with pandemic A/H1N1 (2009) and rhinovirus had similar hospitalization rates, admission rates to the intensive care units, and mortality rates. The common cold can be the cause of prolonged hospitalization and death.
Data such as this underscores the importance of identifying the cause of a respiratory infection. A misdiagnosis could lead to inappropriate or unnecessary treatment. A rhinovirus infection mistakenly identified as influenza or a bacterial infection could lead to the prescription of an antiviral therapy or antibiotic.
Not testing for respiratory viruses also can negatively impact public-health monitoring efforts. Viruses are, if nothing else, unpredictable pathogens. They evolve. They mutate. If we do not actively track the source of a community’s illnesses, we risk missing new outbreaks and lose opportunities to stop the spread of harmful new pathogens.
Luckily, accurate, comprehensive testing for viruses is getting faster and easier to perform. New molecular tests have overcome the limitations that prevented the consistent testing of viruses with cell culture, direct fluorescent antibody (DFA) and enzyme immunoassay (EIA) techniques. These traditional methods have been criticized as too slow to provide clinically relevant results, too cumbersome and not comprehensive enough.
In recent years, technology has converged to provide laboratories with multiplexed molecular virus tests. The tests enable the detection of multiple respiratory viruses at once and can provide results in just a few hours. With these tests, effective testing for respiratory viruses is finally within reach and can become standard healthcare practice, allowing us to improve patient care and virus surveillance.
References
- Cohen E. CNN. “Flu test wrong, girl almost dies.” Published December 3, 2009. http://www.cnn.com/2009/HEALTH/12/03/h1n1.kids.dangers/.
- Centers for Disease Control and Prevention. Weekly U.S. Influenza Surveillance Reports, August 23, 2009-January 2, 2010.
- Sapatkin D. Philadelphia Inquirer. “Ill this fall? Maybe it wasn’t swine flu after all.” Published November 12, 2009.
- Comparison of morbidity and mortality of rhinovirus infection to 2009 pandemic H1N1 influenza A at an academic tertiary referral center. http://shea.confex.com/shea/2010/webprogram/Paper2043.html.
Nancy Krunic, PhD, is vice president at Luminex Molecular Diagnostics.
