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Clinical Laboratories and Pathology Groups

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Anticipated Influenza/SARS-CoV-2 “Twindemic” Has Not Developed, Says CDC, Much to the Relief of the Nation’s Medical Laboratories

The remarkably low number of influenza diagnoses makes it possible for clinical laboratories to stay focused on COVID-19

One positive note for clinical laboratories this winter is the fact that the number of biological samples being submitted for influenza (flu) testing have dropped significantly. This has given medical laboratories more resources for processing COVID-19 tests.

Dark Daily’s sister publication The Dark Report covered this phenomenon in “Surprise! Many Fewer Cases of Flu in Us, Canada, Europe,” December 7, 2020.

According to a feature published in Nature, the number of samples being submitted to medical laboratories for flu testing has dropped by 61%. More surprisingly, the number of positives has dropped by 98%. The combined flu/COVID-19 “twindemic” that some medical experts feared could crush our healthcare system has not materialized—yet, the Washington Examiner reported.

“In any given winter, hospitals are taxed by the flu,” Brian Garibaldi, MD, a pulmonologist and critical care specialist and Medical Director of the Johns Hopkins Biocontainment Unit told the Washington Examiner. “There’s always a concern that our emergency departments will be overwhelmed, and ICU capacity will be strained [due to the concurrence of flu and COVID-19 outbreaks], particularly with people who have coexisting conditions that then get influenza.”

The 2019-2020 flu season ended earlier than usual, likely because of precautions put in place in the spring to combat the coronavirus pandemic. Most years, the seasonal flu in the US peaks in February and trails off by May, Nature reported in “How Coronavirus Lockdowns Stopped Flu in Its Tracks.”

“Seasonal flu cases in the northern hemisphere usually peak in February and tail off by the end of May,” Nature wrote. “This year, unusually, lab-confirmed cases of influenza dropped precipitously in early April, a few weeks after the coronavirus pandemic was declared on 11 March. The data comes from tests of more than 150,000 samples from national influenza laboratories in 71 countries that report data to FluNet, a global surveillance system.”

Government Leaders and Health Experts Remain Concerned

Despite that encouraging data point, public health experts and political leaders were still concerned. In September, Arizona Governor Doug Ducey said, “The overlap of COVID-19 and flu season presents a perfect storm, and we aren’t taking any chances. We are approaching this fall with a proactive mindset and plan of action to limit the impact of the flu and preserve hospital resources,” the Washington Examiner reported.

The caution was certainly warranted. A normal flu season strains resources, but a severe flu season coupled with a global pandemic could have been disastrous. Luckily, Ducey’s “perfect storm” did not materialize.

chart of flu-season during COVID-19 and years 2016 - 2020 with 4 years of flu data charted by FluNet Response System
Data from the World Health Organization’s FluNet Global Influenza Surveillance and Response System was used by Nature to develop the graphic above. It illustrates how the number of positive Influenza specimens in 2019-2020 declined compared to the previous two years. Some experts believe this is due to protocols implemented to combat the COVID-19 coronavirus by hospitals and clinical laboratories. (Graphic copyright: Nature.)

Why Is There Less Influenza?

So, why is there less flu and other respiratory infections?

Epidemiologist Lisa Lockerd Maragakis, MD, MPH, Associate Professor of Medicine and Senior Director of Infection Prevention at Johns Hopkins Health System, told U.S. News, widespread business and school closures provide fewer opportunities for influenza to spread. “We commonly see flu spread in communities, schools, businesses and through travel each year, so those changes are likely keeping the flu away.”

However, this may have a negative effect as well. Eili Klein, PhD, Associate Professor of Emergency Medicine at Johns Hopkins School of Medicine, warns that “Because of the current restrictions and precautions everyone is taking this season, far fewer people will be infected or exposed to the flu virus, and therefore won’t become immune to certain strains of the virus. So, the number of people who may have more severe infections next year is likely to be greater because immunity will be lower,” the Washington Examiner reported.

Other Viral Infections Also in Decline Due to COVID-19 Precautions, Vaccines

Masking, frequent handwashing, and social distancing certainly played a role in reducing the number of cases of flu reported this year. But influenza is not the only disease that saw reductions. “In Hong Kong, compared with previous years, the number of chickenpox cases dropped by about half to three-quarters,” Nature reported. “In April, cases of measles and rubella were their lowest, globally, since at least 2016, according to data available so far.”

Early in the COVID-19 pandemic, some public health officials were concerned that the decline in influenza cases was actually related to a lack of testing. “However, renewed efforts by public health officials and clinicians to test samples for influenza resulted in adequate numbers tested and detection of little to no influenza virus,” the Centers for Disease Control and Prevention (CDC) reported.

Another factor in the lower numbers of flu cases could be due to the fact that more people have gotten vaccinated this year. More than 188 million flu vaccines were distributed in 2020, an increase compared to the 169 million given in 2019.

“Flu vaccination in the community started earlier this year, as recommended by the CDC, and our community physicians report that vaccine uptake has been higher than usual,” Marie-Louise Landry, MD, Clinical Virologist, Professor of Laboratory Medicine and of Medicine (Infectious Diseases), and Director of the Clinical Virology Laboratory at Yale School of Medicine, told Healthline.

It may also be that influenza diagnoses are fewer because people are not seeking treatment. Hospitals at or beyond capacity due to the pandemic, or fear of contracting COVID-19, may have motivated people with flu-like symptoms to stay home rather than seek treatment. However, most healthcare experts agree that public health measures to fight COVID-19 are likely the larger reason there is less flu.

“Public health measures such as movement restrictions, social distancing, and increased personal hygiene likely had an effect on decreasing influenza and other respiratory virus transmissions,” the World Health Organization (WHO) told Nature.

What About the Next Flu Season?

Experts are more conflicted regarding what all of this means for coming flu seasons. Some experts think that because there’s less flu this year, there will be less immunity next year, and severe illness will result. Others are more optimistic and hope that some strains of flu will disappear, which could mean less flu in the immediate future. It’s not a simple prediction to make.

“A lot of different flus have been circulating in recent years. Are they all going to make it out of this or not? It’s possible that what this season will do is actually make the virological picture a lot simpler. That may be permanent, potentially,” Richard Webby, PhD, an infectious disease scientist at St. Jude Children’s Research Hospital and Director of the World Health Organization Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, told Nature in “How COVID-19 is Changing the Cold and Flu Season.”

Even if the low flu numbers this year mean some strains do not survive, it is unlikely that will remain the case. “I am sure that flu will come back with a vengeance at some stage in the future,” Robert Ware, PhD, a biostatistician, clinical epidemiologist, and Professor of Biostatistics with Griffith University in Queensland, Australia, told Nature.

Thus, clinical laboratories should remain vigilant for future influenza outbreaks. Hopefully by then the COVID-19 pandemic will have peaked and labs will be able to reallocate testing resources appropriately.

—Dava Stewart

Related Information:

How COVID-19 Is Changing the Cold and Flu Season

How Coronavirus Lockdowns Stopped Flu in Its Tracks

CDC Reports Record-Low Positive Flu Tests

What Happened to the Flu This Year?

Decreased Influenza Activity During the COVID-19 Pandemic—United States, Australia, Chile, and South Africa, 2020

Why Flu Cases Are Down During a Massive Pandemic