A study from the pandemic’s early days, in January of 2020, profiled 41 hospitalized COVID patients in China and found that 63 percent of them had low numbers of lymphocytes, a critical type of disease-fighting white blood cell.

Then, they train the power of modern biotechnology on the immune system, scanning hundreds or thousands of cells, genes, and molecules for anything that looks different in COVID patients vs. their never-infected counterparts.

When COVID hit, David Lynn, a co-author on that paper and a professor at the South Australian Health and Medical Research Institute and Flinders University, put together a grant application to determine whether SARS-CoV-2 did the same.

One possible explanation for this small-scale perturbation is that long COVID’s symptoms could be the result of a hidden confrontation between the immune system and active virus ensconced deep in the body’s tissues—like combat among soldiers in remote outposts who don’t yet know the war is over.

Chansavath Phetsouphanh, an immunologist at the University of New South Wales’ Kirby Institute, was lead author on an Australian study that found hints of immunological dysfunction at least eight months after infection, particularly in patients with long COVID.

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