Cold and flu season” is one of the great misnomers in
healthcare. Each year, thousands of children and adults cycle through
doctors’ offices and hospitals with nearly indistinguishable sniffles,
sneezes, coughs, and fevers. While their illnesses may be similar, the
truth is these symptoms can be caused by any number of respiratory
viruses that circulate in our communities — from common influenza and
rhinovirus to adenovirus, metapneumovirus, and respiratory syncytial
virus (RSV).
The challenge these viruses present the healthcare
community is that they are virtually impossible to distinguish from one
another based solely on symptoms. One study found that less than 30% of
children were correctly diagnosed with the influenza virus based on
clinical assessment alone. So, a correct diagnosis is dependent on a
laboratory test, in most cases.
How many viruses can really be out there, though? Is
cold and flu season really about more than just cold and flu? You may be
certain that it is. In our laboratory, we found the presence of 12
viruses in patients with similar symptoms — influenzas, parainfluenzas,
RSVs, and rhinovirus. We found dual and triple infections — cases in
which one patient is carrying more than one respiratory virus — as well.
Even with these findings in mind, is distinguishing these viruses from
one another really important? If their symptoms are similar, do we need
to specifically diagnose them? Having studied viruses and their mutation
for many years, my assertion is that diagnosing these viruses is,
indeed, important — to patients, to public health, and to the healthcare
system.
Viruses are, if nothing else, unpredictable. The
2008-2009 cold and flu season was tracking to be a relatively mild one —
pretty uneventful except for the circulation of a Tamiflu-resistant
strain of influenza. And then the month of April introduced us to 2009
influenza A H1N1, or swine flu. With the emergence of new pathogens,
such as the new H1N1 and antiviral-resistant viruses, it is increasingly
important for us to accurately diagnose patients so we can better
monitor the viruses circulating throughout our healthcare facilities and
communities. Benefits of accurate detection of respiratory viruses
include:
- Improved patient care. Early, accurate
diagnosis of respiratory viruses allows doctors to initiate optimal
treatment, which improves patient outcomes. - Reduced unnecessary use of medication.Rapid
and accurate detection of viral pathogens prevents unnecessary use
of antivirals and antibiotics, which lowers treatment expenses and
slows the emergence of antiviral- and antibiotic-resistant
pathogens. - Decreased medical procedures and expenses.
Establishing an etiologic diagnosis prevents unnecessary procedures
for other suspected causes of disease. - Prevention of hospital-acquired infections.Early, accurate detection of respiratory viruses allows for prompt
control of nosocomial outbreaks, which are serious complications of
respiratory infections and have substantial medical and financial
consequences.
How can we better detect and identify respiratory
viruses? Luckily, today, we have a wealth of tools at our disposal.
Until recently, methods available to detect and identify respiratory
viruses were too slow and cumbersome to make them valuable tools. In the
last couple of years, however, more timely and accurate tests have been
introduced. The available testing methods include the following:
- Cell culture: Cell culture is the most
traditional approach to identifying respiratory viruses where cells
are grown under controlled conditions. Although proven to be
accurate, the test can require up to 14 days for results. - DFA: Direct fluorescent antibody is a
laboratory test that uses antibodies with fluorescent dye to detect
the presence of viruses. This test does not detect the full range of
viruses that commonly cause respiratory illness, lacks great
sensitivity, and cannot identify dual infections. - EIA: Enzyme immunoassay techniques are
traditional methods that works to detect the viral antigen; however,
EIA methods are available for only a limited number of pathogens. - Rapid pathogen tests: Rapid flu tests are the
most common of the rapid tests. Widely available and usually easy to
use, rapid tests use antibodies to detect a protein from the virus.
These tests can give results in a matter of minutes and are
inexpensive; without using great care in performing the test,
particularly to diagnose H1N1, the results can be skewed. - PCR: Polymerase chain reaction is a technique
that reproduces and analyzes a short sequence of DNA in order to
detect viruses. Sensitive and specific, PCR-based tests can detect
respiratory viruses and can accurately identify a number of
respiratory viruses as well as detect dual and triple infections.
These tests can take several hours to run, but most can provide
results in less than 24 hours.
In summary, viral respiratory infections are
important causes of disease. Missed infections can cause additional
medical complications, nosocomial infections, and prolonged hospital
stays, contributing to unnecessary healthcare costs as well as increased
patient morbidity and mortality. Inaccurate diagnosis resulting in
overuse of medications is also of particular concern.
Accurate identification of the pathogen — or
pathogens — infecting a patient is essential in order to take effective
clinical action, contain the spread of infection, and contribute to
public-health surveillance efforts.
Steve Kleiboeker, DVM, PhD, is Chief Scientific
Officer at ViraCor Laboratories in Lee’s Summit, MO.
