#16,367
One of the topics we've been following for more than a year is the potential for - and the impact of - dual infection with COVID-19 and Influenza A (or B). Data has been limited, but what we have seen has suggested that a co-infection increases the severity of illness, and the risk of death.
A little over a year ago, in PHE Study: Co-Infection With COVID-19 & Seasonal Influenza, we looked at a Public Health England study that warned that being co-infected with influenza and COVID more than doubled the risk of death over having COVID alone.
While being infected with Influenza lowered the risk of contracting SARS-CoV-2 (likely due to `viral interference'), among those who did contract both, they determined:Authors: J STOWE, PhD 1* , E TESSIER, MsC 1* , H ZHAO, PhD 1 , R GUY, BSc 2 , B MULLER-PEBODY, PhD 2 , M ZAMBON, PhD 3 , N ANDREWS, PhD 4 , M RAMSAY, MBBS, 1 , J LOPEZ BERNAL, PhD 1
`. . . the risk of death was nearly six times greater among individuals with a SARS-CoV-2 and influenza coinfection than those with neither influenza nor SARS-CoV-2 and that this effect is significantly higher than the risk associated with SARS-CoV-2 infection alone.'
Since then, we've seen animal studies (see here and here) that further support these concerns, but the lack of an influenza season last year has limited the amount of real world data on human co-infections.
With influenza (A/H3N2) recently on the ascendent (see CDC HAN # 00458 : Increasing Seasonal Influenza A (H3N2) Activity), COVID Delta still circulating globally, and a new Omicron variant on its way, getting more data on COVID-Flu coinfections takes on new importance this fall.
With the caveat that this study is based on a limited number of cases in Guangdong Province, China between January 2020 and November 2020 - a time before the emergence of any of the COVID variants (Alpha, Delta, Omicron) of concern and when a milder H1N1 flu virus was circulating - this study also finds:
- Co-infection had an increased odds of acute kidney injury, acute heart failure, secondary bacterial infections, multilobar infiltrates and admittance to ICU than monoinfection.
- Co-infection by SARS-CoV-2 and H1N1 caused more severe disease than monoinfection by either virus in adult inpatients.
The full (open access) paper is available on the PloS NTD website. I've only posted the link and some excerpts below. I'll have a brief postscript after the break.
Clinical and virological impact of single and dual infections with influenza A (H1N1) and SARS-CoV-2 in adult inpatients
Jiazhen Zheng, Fengjuan Chen, Keyi Wu, Jiancheng Wang, Furong Li, Shan Huang, Jianyun Lu, Jinghan Huang, Huamin Liu, Rui Zhou, Zhiwei Huang, Bingyao Meng, Zelin Yuan, Xianbo Wu
Published: November 29, 2021
https://doi.org/10.1371/journal.pntd.0009997
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mimics the influenza A (H1N1) virus in terms of clinical presentation, transmission mechanism, and seasonal coincidence. Comprehensive data for the clinical severity of adult patients co-infected by both H1N1 and SARS-CoV-2, and, particularly, the relationship with PCR cycle threshold (Ct) values are not yet available.
All participants in this study were tested for H1N1 and SARS-CoV-2 simultaneously at admission. Demographic, clinical, treatment, and laboratory data were extracted from electronic medical records and compared among adults hospitalized for H1N1 infection, SARS-CoV-2 infection and co-infection with both viruses. Ct values for viral RNA detection were further compared within SARS-CoV-2 and co-infection groups. Score on seven-category ordinal scale of clinical status at day 7 and day 14 were assessed.
Among patients with monoinfection, H1N1 infection had higher frequency of onset symptoms but lower incidence of adverse events during hospitalization than SAR-CoV-2 infection (P < 0.05).
Co-infection had an increased odds of acute kidney injury, acute heart failure, secondary bacterial infections, multilobar infiltrates and admittance to ICU than monoinfection.
Score on seven-category scale at day 7 and day 14 was higher in patients with coinfection than patients with SAR-CoV-2 monoinfection (P<0.05). Co-infected patients had lower initial Ct values (referring to higher viral load) (median 32) than patients with SAR-CoV-2 monoinfection (median 36). Among co-infected patients, low Ct values were significantly and positively correlated with acute kidney injury and ARDS (P = 0.03 and 0.02, respectively).
Co-infection by SARS-CoV-2 and H1N1 caused more severe disease than monoinfection by either virus in adult inpatients. Early Ct value could provide clues for the later trajectory of the co-infection. Multiplex molecular diagnostics for both viruses and early assessment of SAR-CoV-2 Ct values are recommended to achieve optimal treatment for improved clinical outcome.
Author summary
The baseline enrolled 505 patients admitted to Guangzhou Eighth People’s Hospital (Guangzhou, Guangdong) with a diagnosis of COVID-19 or H1N1. All the patients were tested by both viruses at admission. Demographic, clinical, treatment, and laboratory data were extracted from electronic medical records and compared among adults (≥18 years) hospitalized for H1N1 infection (n = 220), SARS-CoV-2 infection (n = 249) and co-infection with both viruses (n = 36).
The prevalence rate of H1N1 co-infection was 12.6% (36/285) among patients hospitalized with COVID-19. Co-infection affected a predominantly older age group and was associated with poorer clinical outcome.
We also described the viral load trajectory in patients with diverse types of infection. Lower initial Ct values (higher viral loads in nasopharyngeal swabs) of co-infected patients was found to be associated with a higher number of adverse events and clinical symptoms.
Considering the COVID-19 pandemic and a simultaneous epidemic of seasonal influenza, the data in China may critically inform future therapeutic or prophylactic strategies, especially for other developing countries.
(SNIP)
Our findings are relevant in the context of the COVID-19 pandemic. Co-infection affected a predominantly older age group and was associated with poorer clinical outcomes. The prevalence rate of co-infections in COVID-19 cases shows the importance of flu vaccination and warrants its increased coverage. Additionally, molecular diagnostic testing for H1N1 virus is recommended for COVID-19 inpatients to provide timely and appropriate treatments for improved outcomes. The Ct value collected with nasopharyngeal swabs in the early stage of co-infection could provide clues for the later trajectory of the disease.
Since this study deals with a milder H1N1 Influenza A virus (in adults) and the `wild type' COVID virus that dominated in during most of 2020 - and was conducted before COVID vaccinations became widely available - it makes direct comparisons to today more difficult.
But it is probably safe to assume that you really, really don't want to endure a dual infection, regardless of the influenza strain or the COVID variant.
Last winter we got lucky, and influenza was a no-show, but this year that appears less likely. All reasons why, even if they aren't 100% effective, it makes sense to get both the COVID and Flu vaccines and to resume wearing face masks in public.
Hospitals are likely to be stretched to their limits this winter due to the expected arrival of Omicron, and in several states Crisis Standards of Care are already invoked (see The Realities Of Crisis Standards Of Care).
Making anything you can do to reduce your odds of being infected with either virus (or both), or hospitalized for any reason, well worth your effort.
