Influenza 2020/2021: Two Studies Show Risks Of Severity Involved With Sequential Infection Of Influenza Followed By COVID-19 Or Even Concurrently
: Two different studies one by Chinese researchers and another led by British scientists show the high risk involved with sequential infection of influenza followed by COVID-19.
In the first study by Chinese scientist from State Key Laboratory of Virology, College of Life Sciences, Wuhan University-Wuhan, team shows that infection with the Influenza A virus or IAV actually enhances susceptibility to the COVID-19 disease along with risk for severity.
According to the study team, the upcoming flu season in the northern hemisphere merging with the current COVID-19 pandemic raises a potentially severe threat to public health. Through experimental co-infection of IAV with either pseudotyped or SARS-CoV-2 live virus, the team found that IAV pre-infection significantly promoted the infectivity of SARS-CoV-2 in a broad range of cell types. Remarkably, increased SARS-CoV-2 viral load and more severe lung damage were observed in mice co-infected with IAV in vivo. Moreover, such enhancement of SARS26 CoV-2 infectivity was not seen with several other viruses probably due to a unique IAV segment as an inducer to elevate ACE2 expression. The study illustrates that IAV has a special nature to aggravate SARS-CoV-2 infection, and prevention of IAV is of great significance during the COVID-19 pandemic.
The study findings were published on a preprint server and have yet to be peer reviewed. https://www.biorxiv.org/content/10.1101/2020.10.14.335893v1
In the second study by led scientist from University of Liverpool, along with support from experts from the University of Zurich, University of Bristol, University of Georgia and Northwest A&F University,Shaanxi-China, evidence was provided that showed the ‘twinfection' of influenza and COVID-19 may exacerbate the health risk associated with COVID-19.
The study found that when multiple pathogens are in circulation at the same time this can lead to cooperative or competitive forms of pathogen-pathogen interactions. This concept of co-infection was evident during the outbreak of the Spanish flu in 1918 with secondary bacterial pneumonia co-infecting many patients suffering from the influenza A virus and causing a more severe outcome.
The study findings were also published on a preprint server and are currently being peer reviewed. https://www.biorxiv.org/content/10.1101/2020.10.13.334532v1
There recently have been several case reports of co-infections with influenza and SARS-Cov-2 in humans with COVID-19. One study from the UK reported that patients with a co-infection exhibited up to six times higher risk of death.
In order to ascertain the health risks associated with the 'twinfection' , the study team sequentially co-infected mice with influenza and SARS-CoV-2.
The study was led by Professor Dr James Stewart and Professor Dr Julian Hiscox
from the University of Liverpool's Institute of Infection, Ecological and Veterinary Sciences.
The infected mice mirror many features of severe COVID-19 infection in humans and are a model used to develop understanding of lung disease and to test pharmacological interventions.
It must be noted that animal models of COVID-19 present critical tools to fill knowledge gaps for the disease in humans and for screening therapeutic or prophylactic interventions. While animal models can't predict with total accuracy the consequences of co-infection in humans, the data presented will have implications for development of successful pre-emptive interventions for SARS-CoV-2 and the clinical management of COVID-19.
The study found that the infection of mice with these viruses resulted in disease and then recovery. However, sequential infection with influenza virus and then SARS-CoV-2 displayed overt clinical symptoms that were worse than the individual infections.
Importantly in the sequentially infected mice, whilst the replication of SARS-CoV-2 was diminished compared to mice infected with this virus alone, there was an enhanced inflammatory response. This is a key driver for severe COVID-19 infection in humans and plays a significant role in mortality.
Alarmingly it was found that sequentially infected mice exhibited significantly more rapid mortality compared with mice infected with either virus alone. These results suggest that infection with both viruses leads to an exacerbation of pathological processes.
This new evidence highlights important implications for the ongoing pandemic. As countries across the globe come out of a period of lockdown, the rate of infection of SARS-CoV-2 is likely to increase and as many countries head toward flu season, attention should be focused not only slowing the transmission of SARS-CoV-2 but also reducing influenza infections as part of a comprehensive public health response to mitigate the effects of co-infection.
Dr Stewart said: "There is growing concern about the interactions between SARS-CoV-2 and other respiratory infections in the upcoming winter season. Our study highlights the urgent need to maintain flu vaccination and gives a way to be able to explore effective interventions
Dr Hiscox further added, ''Seasonal influenza virus can overwhelm the NHS on normal years. Both SARS-CoV-2 and influenza are likely to co-circulate and present a risk. Our work shows how infection with both is dangerous and we can at least do something about mitigating the risk of flu through vaccination
Flu vaccinations are going to play a critical role in this coming influenza season and the key take away from both studies is that not only is it critical for vulnerable groups or those more at risk to have their flu shots but basically anybody who can do so should have themselves vaccinated for the influenza as soon as possible.
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