But other factors could be damaging the brain. For example, a cytokine storm could cause brain swelling, and the blood’s exaggerated tendency to clot could trigger strokes. The challenge now is to shift from conjecture to confidence, at a time when staff are focused on saving lives, and even neurologic assessments like inducing the gag reflex or transporting patients for brain scans risk spreading the virus.
Last month, Sherry Chou, a neurologist at the University of Pittsburgh Medical Center, began to organize a worldwide consortium that now includes 50 centers to draw neurological data from care patients already receive. The early goals are simple: Identify the prevalence of neurologic complications in hospitalized patients and document how they fare. Longer term, Chou and her colleagues hope to gather scans, lab tests, and other data to better understand the virus’ impact on the nervous system, including the brain.
Chou speculates about a possible invasion route: through the nose, then upward and through the olfactory bulb—explaining reports of a loss of smell—which connects to the brain. “It’s a nice sounding theory,” she says. “We really have to go and prove that.” Most neurological symptoms “are reported from colleague to colleague by word of mouth,” Chou adds. “I don’t think anybody, and certainly not me, can say we’re experts.”
Her case adds to a growing body of evidence suggesting the new coronavirus, like its cousin SARS, can infect the lining of the lower digestive tract, where the crucial ACE2 receptors are abundant. Viral RNA has been found in as many as 53% of sampled patients’ stool samples. And in a paper in press at Gastroenterology, a Chinese team reported finding the virus’ protein shell in gastric, duodenal, and rectal cells in biopsies from a COVID-19 patient. “I think it probably does replicate in the gastrointestinal tract,” says Mary Estes, a virologist at Baylor College of Medicine. “The lung is the primary battle zone. But a fraction of the virus possibly attacks the kidney. And as on the real battlefield, if two places are being attacked at the same time, each place gets worse,” says Hongbo Jia, a neuroscientist at the Chinese Academy of Sciences’s Suzhou Institute of Biomedical Engineering and Technology and a co-author of that study.
Viral particles were identified in electron micrographs of kidneys from autopsies in one study, suggesting a direct viral attack. But kidney injury may also be collateral damage. Ventilators boost the risk of kidney damage, as do antiviral drugs including remdesivir, which is being deployed experimentally in COVID-19 patients. Cytokine storms also can dramatically reduce blood flow to the kidney, causing often-fatal damage. And pre-existing diseases like diabetes can boost the risk of AKI. “There is a whole bucket of people who already have some chronic kidney disease who are at higher risk for acute kidney injury,” says Suzanne Watnick, chief medical officer at Northwest Kidney Centers.
Chou speculates about a possible invasion route: through the nose, then upward and through the olfactory bulb—explaining reports of a loss of smell—which connects to the brain. “It’s a nice sounding theory,” she says. “We really have to go and prove that.”