Monday, March 02, 2026

Nature Comms: The Risk of Kidney Disease Increases Following SARS-CoV-2 Infection Compared to influenza

 

Nature Med. Review: Extrapulmonary manifestations of COVID-19

#19,071

Now that 90% of the world's nations are no longer reporting COVID infections, hospitalizations, and deaths (see No News Is . . . Now Commonplace), the current health burden of COVID infection is largely obscured.  
Estimates put the number of U.S. daily infections at > 90K (see Estimated Burden of COVID-19 Illnesses, Medical Visits, Hospitalizations, and Deaths in the US From October 2022 to September 2024), but with limited testing, no one really knows.  

Even though COVID has lost much of its initial lethality, the above study suggests it caused 1.1 million hospitalizations, and 101 300 deaths in the U.S. during the study period.

Also not reliably counted are the long-term impacts of (often repeated) COVID infection.  `Long-COVID' - or Post COVID Syndrome - has been estimated to affect up to 20% of survivors. 


Research also suggests that with each SARS-CoV-2 reinfection, the risks of complications or developing Long COVID increase. With fewer people getting vaccinated/boosted, and fewer still bothering with NPIs, multiple reinfection's are increasingly commonplace. 

While world governments (and the general public) seemingly don't want to hear about it, the evidence of long-term harm from repeated (even mild) COVID infection continues to mount.  

A few (of many) recent studies include:


EHJ: Accelerated Vascular Ageing After COVID-19 Infection: The CARTESIAN Study

To this growing preponderance of evidence we can add a new study, just published in Nature Comms, which finds increases in both acute kidney injury (AKI) and chronic kidney disease (CKD) following COVID infection. 

Those with long memories will recall that we first saw evidence of COVID infection's impact on the kidneys more than 5 years ago (see JASN: Acute Kidney Injury In Hospitalized Patients With COVID-19).

This wasn't entirely surprising, since the SARS-CoV-2 virus enter cells via ACE2 receptors, which are particularly abundant in numerous renal tubules in human kidneys. Many early studies reported a high rate of AKI and CKD following COVID hospitalization. 

Since the full edited version of this study hasn't been posted, I'll simply post the following abstract and summary.  Follow the link to read it in its entirety. 

I'll have a bit more after the break.

The risk of kidney disease increases following SARS-CoV-2 infection compared to influenza
Communications Medicine , Article number: (2026) Cite this article

We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

Abstract

Background

Although case reports and observational studies suggest COVID-19 increases the risk of kidney diseases, real-world evidence comparing it with influenza is limited. Our study aims to assess the association between COVID-19 infections and subsequent kidney diseases, using influenza as a positive control and incorporating a negative control to establish clearer associations.

Methods

A large retrospective cohort study with strata matching was conducted using the MarketScan database with records from Jan. 2020 to Dec. 2021. We used the ICD-10 codes to identify individuals and build three cohorts: (1) COVID-19 group, (2) Positive control group: Influenza but no COVID-19, and (3) Negative control group: no COVID-19 / Influenza. The outcomes were acute kidney injury (AKI), chronic kidney disease (CKD), end-stage renal disease (ESRD), and glomerular diseases. Multivariable stratified Cox proportional hazards regression analyses were performed.

Results

The study includes 939,241 individuals with COVID-19, 1,878,482 individuals in the negative control group, and 199,071 individuals with influenza. COVID-19 is significantly associated with increased risks of AKI (adjusted hazards ratio, aHR: 2.74; 95% CI, 2.61-2.87), CKD (aHR: 1.38, 1.32-1.45), ESRD (aHR: 3.22, 2.67-3.88), and glomerular diseases (aHR:1.28, 1.09-1.50), while influenza has no impact on CKD, ESRD, and glomerular diseases. Time-specific analyses indicate that COVID-19 has stronger effects on AKI in the short term but has stable long-term effects on CKD.
Conclusions

In this large real-world study of working-age, commercially insured adults in the United States, COVID-19 infection is associated with a 2.3-fold risk of developing AKI, a 1.4-fold risk of CKD, and a 4.7-fold risk of ESRD compared to influenza. Greater attention to kidney diseases post-COVID-19 is essential to prevent future adverse health outcomes.

Plain Language Summary

COVID-19, caused by the SARS-CoV-2 virus, has been linked to multiple organ complications, with emerging evidence suggesting effects on kidney diseases. However, it is unclear how the risk of kidney disease after COVID-19 compares with influenza, another common viral infection. In this study, we analyzed commercial health insurance data from over three million working-age adults in the United States to compare individuals with COVID-19, those with influenza, and those with neither infection. We found that individuals who had COVID-19 were more likely to develop kidney problems, including short-term injury and long-term chronic disease. These findings suggest that COVID-19 may have a stronger impact on kidney diseases than influenza, highlighting the need for greater attention and monitoring of kidney function after COVID-19 infection.

For a variety of economic, societal, practical, and political reasons the world decided more than 3 years ago that COVID should be treated as a `mild, almost trivial flu-like' illness. 

And while it is true that > 99 out of every 100 COVID cases survives, disability claims have skyrocketed (see CSIRO Pub: Impacts of Long COVID on Disability, Function and Quality of Life for Adults Living in Australia), and chronic illnesses are increasing.

Based on limited data, the WHO estimates that 1 in 6 people who contract COVID will develop some degree of `Long COVID'. Globally, that suggests > 400 million people, and > 20 million in the United States.

Which is one of the reasons why, as recently as late December, we saw a WHO Statement: COVID-19 Still Causes Severe Disease & Renewed Vaccination Recommendations.

 But it is unclear, at this late stage, whether anyone is still listening. 

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