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JAMA Insights
Clinical Update
August 14, 2020

Influenza in the COVID-19 Era

Author Affiliations
  • 1Division of Infectious Diseases, Brigham and Women’s Hospital, Boston, Massachusetts
  • 2Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Healthcare Institute, Boston, Massachusetts
JAMA. Published online August 14, 2020. doi:10.1001/jama.2020.14661

The annual influenza epidemic substantially affects health care systems worldwide and has resulted in an estimated 12 000 to 61 000 deaths annually since 2010 just in the US.1 The extent of the morbidity and mortality in any given year reflects the degree of genetic drift or shift in the dominant strain of the influenza virus and the efficacy and coverage of vaccination. With the coronavirus disease 2019 (COVID-19) pandemic, clinicians face a second respiratory virus associated with morbidity and mortality several-fold higher than that of influenza, in part due to its spread in an immunologically naive population. A looming threat of concurrent influenza and COVID-19 epidemics is a major concern for public health officials and clinicians.

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    3 Comments for this article
    Covid-19 and Influenza
    Zachary Palace, MD | Hebrew Home at Riverdale
    The authors raise a very important point regarding simultaneously testing for both Covid-19 and influenza. Treatment algorithms are so different between these two infections. This makes rapid diagnosis a critical component of initiating proper infection control practices in skilled nursing facilities, and avoiding outbreaks. If the current healthcare facility infection control precautions remain in place, perhaps we will experience less influenza this season as well. Encouraging all staff to get seasonal flu vaccines and promoting frequent handwashing remain the best evidence-based practices we have.
    Reduction in Seasonal From COVID-19 Prevention Measures
    Takuma Hayashi, MBBS, D.Med.Sci., GMRC, | National Hospital Organization, Kyoto Medical Center
    In February and March 2020, when coronavirus infectious disease-2019 (COVID-19) spread rapidly throughout Japan, it was the time of seasonal influenza infection. Is it possible to have these two infectious diseases at the same time? Influenza virus infection is common to the respiratory tract of cells on top of the from the nose to the larynx. On the other hand, the SARS-CoV-2 infects cells in the back of the lung in addition to the upper respiratory tract and causes pneumonia. These two infectious diseases are completely different diseases. Therefore, when both viruses are exposed to humans in a short period of time, it is highly conceivable that both viral infections will occur at the same time, as in the case reported in Wuhan. Hand washing is the basic protection against these viral infections.

    This season (2019-2020), the National Institute of Infectious Diseases reported that the number of patients infected with the seasonal influenza virus in Japan was estimated to be about 7.3 million, or about 60% of those from 2018-2019. In the week when the epidemic of seasonal influenza infection reached its peak (December 23 to 29, last year), approximately 5,000 fixed-point medical institutions nationwide reported the lowest number of seasonal influenza cases in the last 12 years. In other words, the cumulative number of influenza cases nationwide in 2020 (estimated by the Ministry of Health, Labor and Welfare, as of March 29, 2020) decreased to about 40% of the same period of the previous year (about 10.64 million).

    As seasonal influenza virus epidemics infect humans, two A-types and one B-type; total of three influenzas virus types have been reported. Different types of seasonal influenza viruses are prevalent each year. Often, two or three seasonal influenza viruses simultaneously spread. However, type A (H1N1) accounted for more than 90% of the influenza epidemics this season (2019-2020). In other words, almost one type of seasonal influenza virus was prevalent this season. This season, due to the influence of the SARS-CoV-2, people are thoroughly washing their hands and wearing masks. The protective actions against the viral infection are likely to have contributed to the reduction in the number of seasonal influenza patients.
    Comparison Between Seasonal Influenza and SARS-CoV-2 Table
    Jean-Francois Grenier, MD |
    The purpose of this article is valuable. However, when reading "Table. Comparison Between Seasonal Influenza and SARS-CoV-2", there seems to be a few short cuts. or fragile statements:

    1) The authors state that patients are most infectious 48 hours before becoming symptomatic. While they provide a reference, the case report they refer to is a bit light and based on very small numbers. I would refer them to the literature review (34 studies) conducted by Christina Savvides and Robert Siegel, who concluded "different approaches to determining the presence and prevalence of asymptomatic and presymptomatic SARS-CoV-2 transmission have notable
    shortcomings, which were highlighted in this review and limit our ability to draw definitive conclusions (1)."

    2) Based on the rather weak evidence deriving from current clinical trial published results, stating that remdesivir is an available antiviral treatment is at least premature.


    1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7310638/