Flu season approaches in the northern hemisphere. This incontrovertible reality is challenging enough on its own, but this year, it will arrive while a different virus continues to tax medical systems around the world. What can we expect from the combined impact of these two viruses as they collide in our public spaces and our hospitals? Dr. Manoj Gandhi, the Senior Medical Director of Thermo Fisher Scientific’s Genetic Testing Solutions business unit, has some thoughts.
What do we already know about influenza?
Influenza is a group of related viruses that, in the northern hemisphere, have cyclical peaks and troughs of infection that coincide with the seasons. The autumn/winter flu season is arriving now in many countries where there are still high incidences of SARS-CoV-2 infections. As a virus that has only recently begun to infect humans, SARS-CoV-2 does not show any seasonal patterns and seems likely to continue maintaining high infection rates as flu cases increase. This combination poses a special challenge for medical systems.
Regarding influenza, Dr. Gandhi says, “Influenza was first described about 100 years ago, but has been around for centuries. We are now armed with vaccines for influenza as well as treatments like Tamiflu that, when provided within the first two days following presentation of influenza symptoms, can be very effective.”
Nevertheless, influenza remains a serious pathogen, especially because its high mutation rate means that acquired immunity does not offer enduring protection against the whole class of influenza viruses. In addition, new subtypes can be more virulent and potentially lead to higher mortality rates than their predecessors.
The seasonal emergence of new flu subtypes and waves of infections and hospitalizations will likely coincide with the ongoing high incidence of SARS-CoV-2 infections in many countries. This coincidence of timing presents two major challenges to medical systems: patient load and disambiguation.
Patient management for influenza and SARS-CoV-2
Hospital systems in the United States, Canada and other countries historically have time to prepare for flu season, stocking up on relevant resources in anticipation of influenza patients. They could reasonably expect and plan for the surge of patients and then the return to baseline conditions afterward. That increase in capacity is, for many medical institutions, not nearly as available as it was in previous years. Many systems have been stretched to and beyond their limits responding to ongoing SARS-CoV-2 infections, with no extra capacity available to prepare for the upcoming arrival of influenza cases. For hospitals struggling to care for an already elevated number of respiratory patients and scrambling for enough resources to keep illnesses from spreading in their halls, a second, unrelated wave of infections is a frightful prospect.
The ongoing hazard of the coronavirus crisis is having one surprising effect with regard to influenza, however. The widespread use of social distancing, masks and other protective measures against SARS-CoV-2 seems to be reducing the transmission of influenza and other seasonal respiratory viruses as well. Preliminary signs from Japan, Taiwan and a few other countries suggest that these measures may result in a milder than usual flu season if they are maintained for at least the next several months.
How do you distinguish between SARS-CoV-2 and influenza infections?
Dr. Gandhi explains the challenge of distinguishing these two conditions in a therapeutic context: “The problem is that they present with very similar symptoms, such as fever, cough, body aches, runny nose. There are some subtle differences such as loss of taste or smell and shortness of breath that may be seen in COVID patients. However, [these] may not be seen in all patients, and, for the most part, the symptoms between COVID and flu are strikingly similar. So, the issue becomes how can the physician distinguish one versus the other? And the answer is that one needs to perform a test.”
Given that many of the therapeutic approaches for the two conditions, including the use of ventilators, are based on the symptoms that they share, that test might seem superfluous. Treatment specific to symptoms, by and large, does not have to be especially concerned with what is causing the symptoms, only that it can alleviate them. However, not all treatments for these two conditions are limited to their symptoms; drugs and protocols exist that target the infections directly. These do have to be distinguished by condition because their effects may make them useless or dangerous to one set of patients and lifesaving for the other. Mistaking one for the other is risky to patients and must be avoided.
In particular, one of SARS-CoV-2’s trademarks is that it can induce a cytokine storm due to overstimulation of the immune system, which is rare in influenza patients. The drugs used to treat cytokine storms are immunosuppressants that are contraindicated for influenza, reducing the patient’s ability to fight the virus instead of protecting them from its effects. Similarly, a variety of antiviral drugs are approved for use against SARS-CoV-2 that have not been tested for efficacy or safety against influenza (remdesivir), and vice versa (oseltamivir, zanamivir, peramivir, baloxavir).
Additionally, quarantining procedures for the two viruses are different, with those procedures being much more stringent for those infected with SARS-CoV-2. Being able to accurately reserve the strictest quarantine measures for COVID-19 patients means fewer resources will be needed overall, enabling the system to continue functioning despite higher than normal patient loads.
These aspects of treatment for the two viruses make co-infection, being infected with the two viruses simultaneously, a serious complication that will require specialized procedures to combat.
What if someone has both infections?
Statistically, based on what we know at this moment, the chance of a patient being infected with SARS-CoV-2 and influenza at the same time is low. It is much more likely for a person to have had one, recovered, and then present at a hospital with the other, and for this fact to complicate their blood tests. This scenario presents many of the same challenges as distinguishing between the two infections, due to differing treatment regimens.
What about the flu vaccine?
The fact that flu vaccines exist and can be optimized each year for the strains predicted to be abundant that year is a crucial defense against the flu. Flu vaccines provide protection against the worst of influenza’s impacts and limit this virus’s spread through a population. Even when influenza vaccines do not provide complete protection against an infection (their effectiveness each year varies from ~40–60%), they generally reduce disease severity, helping keep infected people out of the hospital. In a year when the resources available to treat people with serious influenza cases are unusually scarce, maintaining high vaccination levels is critical. High vaccination rates against influenza will also reduce the need to distinguish between influenza and SARS-CoV-2 infections and will especially reduce the chances of patients who present with both simultaneously.
Unfortunately, it is very unlikely that influenza vaccines are effective against SARS-CoV-2 directly. As Dr. Gandhi notes, “The influenza virus belongs to the Orthomyxoviridae family, whereas SARS-CoV-2 belongs to the Coronavirus family, and there are differences between the structure of the two viruses such that each requires its own specific vaccine.” But one especially hopeful possibility is that perhaps a future SARS-CoV-2 vaccine could be administered in the same injection as future flu vaccines, reducing the number of injections needed to protect the population against both diseases.
What is the role of Thermo Fisher Scientific and other test makers in all of this?
Dr. Gandhi explains that “it is up to companies like Thermo Fisher Scientific to make the tests to serve the needs of the physicians, and more importantly, the patients.” Thermo Fisher Scientific’s TaqPath COVID-19 test received Emergency Use Authorization (EUA) earlier this year, as well as CE marking in Europe, and is already in widespread use throughout the world.
With the flu season already upon us, Thermo Fisher Scientific is also developing multiplex PCR tests that will simultaneously detect RNA from multiple respiratory viruses, including SARS-CoV-2, influenza A, influenza B, and more. Combining targets for each of these viruses into a single test makes distinguishing these infections much easier and can help physicians choose the appropriate treatments and protocols for their patients, ultimately saving lives. Dr. Gandhi concludes: “We’ve placed a lot of effort and emphasis here at Thermo Fisher Scientific on helping our customers respond to the COVID-19 pandemic, and we’re proud to be able to continue to help our them meet the demands of respiratory virus testing as we move into flu season.”
To request more information about Thermo Fisher Scientific’s SARS-CoV-2 and influenza multiplex real-time PCR assays, visit us at thermofisher.com/covid-flu.
And to learn more about our growing portfolio of COVID-19 testing solutions, visit us at thermofisher.com/covid19.