Avian Flu Diary: Nature: Co-infection of SARS-CoV-2 & Influenza Causes More Severe and Prolonged Pneumonia in Hamsters

(A) Body weight changes in Syrian hamsters during infection

#16,291

Although we've seen a few studies suggesting that coinfection with SARS-CoV-2 and Influenza A (or B) may produce more lethal outcomes (see PHE Study: Co-Infection With COVID-19 & Seasonal Influenza), the limited circulation of seasonal flu globally over the past 18 months has allowed for relatively few human studies.

We've seen some animal studies (see Nature: Increased Lethality in Influenza & SARS-CoV-2 Coinfection is Prevented by Influenza Immunity but not SARS-CoV-2 Immunity (in mice), but there is an old research adage that `Mice lie and monkeys exaggerate', which means these substitutes may not always provide data that is 100% applicable to humans.

Still, in the absence of better data, animal studies can sometimes produce useful results.

Hamsters have been proven to be susceptible to SARS-CoV-2 infection (see Animal Models for COVID-19), and develop pneumonia similar to humans. Hamsters have also been used to study human disease, including influenza, making them a logical choice for coinfection studies.

All of which brings us to a recent study, published in Nature Scientific Reports, demonstrating the impact of coinfection of COVID19 and Influenza (mouse-adapted influenza A/Puerto Rico/8/34 (H1N1) virus (PR8)) on hamsters. I've only posted some excerpts from this open-access study, so you'll want to follow the link to read it in its entirety.

That said, this research provides more reasons to be concerned over the co-circulation of COVID and seasonal flu, and the potential of co infection in humans. Scenarios that have increasingly become talking points by public health agencies over the past couple of months (see here, here, and here).

Co-infection of SARS-CoV-2 and influenza virus causes more severe and prolonged pneumonia in hamsters
Takaaki Kinoshita, Kenichi Watanabe, Yasuteru Sakurai, Kodai Nishi, Rokusuke Yoshikawa &
Jiro Yasuda

Scientific Reports volume 11, Article number: 21259 (2021) Cite this article

Abstract

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently a serious public health concern worldwide. Notably, co-infection with other pathogens may worsen the severity of COVID-19 symptoms and increase fatality.

Here, we show that co-infection with influenza A virus (IAV) causes more severe body weight loss and more severe and prolonged pneumonia in SARS-CoV-2-infected hamsters. Each virus can efficiently spread in the lungs without interference by the other.

However, in immunohistochemical analyses, SARS-CoV-2 and IAV were not detected at the same sites in the respiratory organs of co-infected hamsters, suggesting that either the two viruses may have different cell tropisms in vivo or each virus may inhibit the infection and/or growth of the other within a cell or adjacent areas in the organs. Furthermore, a significant increase in IL-6 was detected in the sera of hamsters co-infected with SARS-CoV-2 and IAV at 7 and 10 days post-infection, suggesting that IL-6 may be involved in the increased severity of pneumonia.

Our results strongly suggest that IAV co-infection with SARS-CoV-2 can have serious health risks and increased caution should be applied in such cases.

(SNIP)

Discussion

In this study, we showed that co-infection of IAV in SARS-CoV-2-infected hamsters causes more severe body weight loss, delayed recovery, and more severe and prolonged pneumonia than those observed with single infection by SARS-CoV-2 (Table 1). This finding suggests a correlation between body weight loss and the severity of pneumonia determined by micro-CT imaging. Consistent with these enhancements of pathology, co-infected hamsters showed pathological features of both IAV and SARS-CoV-2 infections and high levels of IL-6.

(SNIP)

The hamsters co-infected with SARS-CoV-2 and IAV showed more severe and prolonged pneumonia. This observation is also consistent by a case report of a co-infected patient (32-year-old man) who exhibited severe pneumonia and died of persistent respiratory failure22. Clinical report also showed that COVID-19 patients with influenza exhibited more severe inflammation and organ injury23. However, another report suggested that co-infection with influenza was not associated with increased disease severity of COVID-19 pneumonia24. Therefore, further studies might be needed to understand effects of co-infection on patients.

Taken together, our data strongly suggest that co-infection with IAV poses a serious risk to SARS-CoV-2 infected patients and should be taken into consideration in the treatment and management of these patients.

(Continue . . . )

While no one knows for certain what a `twindemic' of influenza and COVID would look like - or if it will happen this year - but yesterday China's CDC published a long perspective (see China CCDC Weekly: Public Health Control Measures for the Cocirculation of Influenza and SARS-CoV-2 During Influenza Seasons) on the possibilities.