Beyond Lab Consulting

Influenza Invasion: Testing Can Help Lead the Charge in the Fight Against the Flu

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By Cat Troiano

This year’s flu season is well underway, normally peaking during the months of December through February. Over the course of the 2017-2018 season, there were 185 influenza-related pediatric deaths, and more than 30,000 individuals in the United States were hospitalized due to influenza. A number of diagnostic tests are now available for helping to diagnose influenza patients, and some of these tests can achieve an earlier diagnosis for more prompt initiation of treatment. This, in turn, can help to reduce the mortality rate and the number of hospitalizations that result when complications of the virus set in.

A Few Flu Facts

Influenza, commonly referred to as the flu, is a contagious and potentially serious viral respiratory infection that is transmitted through aerosolized droplets and surface contact.
While there is some overlap in many of the symptoms of the flu and those of a cold, one distinction between the two is the sudden onset of the flu when it strikes, unlike a cold’s gradual presentation. Another distinction is that most, but not all, patients who have the flu will run a fever and experience chills. Other symptoms of the flu include:

• Muscle aches
• Headaches
• Cough
• Chest discomfort
• Lethargy
• Sore throat
• Nasal congestion or nasal discharge

Vomiting and diarrhea can also present in some influenza cases, especially in pediatric patients.

While the majority of patients recover from the flu without additional misery, the illness can pose further complications to some individuals, including:

  • Pediatric patients under the age of five years
  • Senior patients aged 65 years or older
  • Pregnant women
  • Residents of long-term care facilities
  • Patients with obesity
  • Patients with compromised immune systems, such as those with cancer, HIV or AIDS
  • Patients who suffer from any of a number of chronic conditions, including asthma, diabetes, coronary artery disease or cardiorespiratory disease

Some of the complications that can result from influenza include sinus infections, bronchitis and pneumonia, which can be fatal in these high-risk patients.

A Virus by Any Other Name

There are two types of flu viruses, which are known as influenza A and influenza B, that are the common culprits for flu outbreaks among the human population each season. However, there are numerous subtypes of influenza A, each identified by its specific protein makeup. Two proteins that are analyzed to identify these subtypes are hemagglutinin and neuraminidase. To date, subtypes H1 through H18 as well as N1 through N11 have been identified. H1N1 and H3N2 are the most prevalent subtypes of influenza A that are currently affecting human patients.

There are also influenza types C and D. Influenza C typically causes a much milder respiratory infection and is not believed to lead to an epidemic. Influenza D is infects cattle and is not known to pose a health threat to humans.

Influenza A and B viruses mutate into new strains through processes known as antigenic drift, which is a slower and more gradual process, and antigenic shift, which takes place more abruptly. In both antigenic drifts and antigenic shifts, the genetic material of the virus undergoes changes when the virus replicates. It is the evaluation influenza antigenic properties that enables the identification of presently circulating flu virus strains and then guides in the formulation of influenza vaccine to be administered for combating the flu during the following season. The results of influenza testing can also provide this valuable data.

Timely Influenza Tests

If a patient presents with the aforementioned flu symptoms, performing an influenza test can serve four purposes:

  • Rule out other illnesses than may be causing the symptoms
  • Enable the proper flu treatment sooner if the test is positive or avoid unnecessary drug therapy if the patient is negative
  • Guide the physician toward the safest course of recommended treatment for patients who are high-risk individuals for developing complications
  • Keep tabs on the potential for localized outbreaks of a flu virus in order to prompt recommendations for preventative measures

There are several influenza tests available. Traditional culturing and other tests can take hours to days to generate results. However, there are two tests that can be performed onsite which generate results in minutes.

The rapid influenza diagnostic test is an antigen detection test. The test is able to screen for influenza in a specimen taken from a nasopharyngeal, nasal or throat swab or aspirate. The rapid influenza detection test provides positive or negative results in as little as 15 minutes. Depending upon the specific test that is used, some rapid influenza diagnostic tests can detect both influenza types A and B.

The rapid molecular assay test detects the presence of influenza RNA, or nucleic acid. This test analyzes a specimen from a nasopharyngeal or nasal swab for influenza types A and B, providing a positive or negative result in 15 to 30 minutes.


One drawback of the rapid influenza diagnostic test is a high incidence (30 to 50%) of false-negative results. However, if a symptomatic patient’s test generates a negative result and his or her primary care physician strongly suspects influenza as the cause of the symptoms, the Center for Disease Control and Prevention (CDC) advises initiating flu treatment while pursuing a second test, either through the more sensitive and specific rapid molecular assay test or a viral culture test, for confirmation of the illness.

It should be noted that a patient who received the live attenuated influenza vaccine within the previous seven days are likely to receive a positive result on a rapid influenza diagnostic test, even if they are not contagious with the influenza virus. Depending on which rapid influenza diagnostic test is used, some will detect the vaccine strains for even longer than seven days.

For the most accurate results, patients should be tested within three to four days of the onset of their symptoms. Patients who can be treated for the flu with anti-viral drug therapy will gain the greatest benefits, including a shorter duration of the illness, a reduction in the severity of their symptoms and a reduced chance of developing complications, when treatment is begun early in their illness.

Prevention Through Vaccination

The first proactive step toward flu prevention is for patients to be vaccinated against the seasonal flu virus. The CDC recommends that every individual six months of age and older should receive the influenza vaccine. Several variations of the vaccine are available to accommodate different age groups and patient health needs for maximum safety and efficacy. Influenza vaccines are tailored each year to combat recent active strains of the illness. Therefore, everyone must be inoculated annually. Pregnant women are more prone to serious illness as a result of contracting the flu virus, and the flu places their unborn baby at risk for premature labor and delivery. The flu vaccine offers protection for the pregnant women and for their developing fetuses.

Additional Preventative Measures

In addition to vaccination, physicians should advise patients to practice the following habits to enhance their immune system’s ability to fight off the flu virus:

  • Wash hands often and thoroughly.
  • Refrain from close personal contact with anyone who has the flu.
  • Avoid interacting with someone who has the flu as much as possible.
  • Continue to eat a nutritionally balanced diet, and engage in regular physical fitness routines.
  • Keep stress levels to a minimum, and get plenty of sleep.

Reduce the Spread

Anyone who contracts the influenza virus should stay home from work or school to avoid spreading the illness to others. These additional measures should be followed to reduce contamination and spread:

  • Patients should cover their nose and mouth with tissues when they cough and sneeze.
  • Patients should refrain from close personal contact with others.
  • Patients should avoid touching their nose, mouth or eyes. Doing so and then touching other surfaces spreads the germs.
  • To reduce the viability of aerosolized flu viruses, maintain a relative humidity level of 40 percent or higher in the home. The higher the air humidity is, the lower the chances are that the flu virus will thrive. This is why flu season peaks during the colder months of low climatic humidity and increased dryness in the air that results from indoor heating systems.
  • Use a disinfectant that has been approved by the Environmental Protection Agency as being effective at killing the influenza virus to wipe down countertops and frequently handled objects, including doorknobs, remote controls, keys and key fobs, faucet handles, toilet flush handles, light switches, tablets, phones, door handles, desktop computer keyboards and control panels on refrigerators, microwaves and coffee machines, etc.

According to the CDC, the influenza virus infects 5 to 20 percent of the United States population each season, and up to 200,000 individuals are admitted annually to hospitals as a result of its complications. A combination of preventative measures and early testing of symptomatic patients can reduce that number of hospitalizations as well as the flu’s severity and duration.

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