About half of hospitalized coronavirus patients experience neurological symptoms including dizziness, difficulty concentrating, a loss of smell and taste, seizures, strokes, and weakness, according to a new review of research published in the Annals of Neurology.

The findings illustrate that COVID-19, the disease the coronavirus causes, is far more than a respiratory infection and rather one that poses “a global threat” to the whole nervous system, including the brain, spinal cord, and nerves, the study authors say.

“It’s important for the general public and physicians to be aware of this, because a SARS-CoV-2 infection may present with neurological symptoms initially, before any fever, cough or respiratory problems occur,” lead study author Igor Koralnik, professor of neurology at Northwestern University Feinberg School of Medicine, said in a press release.

Some of the other neurological symptoms patients experienced included headache, decreased alertness, and muscle pain.

It makes sense that the nervous system can be affected by COVID-19 if, for example, the virus’s wear on the lungs and heart make it tough to get enough oxygen to the brain.

That in turn can contribute to the strokes some COVID-19 patients have experienced.

The virus may also infect the brain directly, the study authors say, and the immune system’s reaction to it can cause inflammation that damages the brain and nerves.

It’s too soon to know much about if or how long the neurological consequences persist and for whom, but Koralnik and his colleagues are planning to find out by continuing to follow COVID-19 survivors who were treated at their hospital.

Other studies and experts have called attention to the short- and long-term cognitive consequences

The current study helps frame and begin to explain something many doctors, patients, and mental-health providers have called attention to: The seemingly large rates and persistence of short- and long-term cognitive complications of COVID-19.

One study suggested as many as 65 percent of COVID-19 patients experience delirium, an often terrifying post-ICU effect that can involve vivid hallucinations, disorientation, irritability, and range of other startling cognitive changes. One expert called delirium an “epidemic” on its own.

Hospitalized COVID-19 patients may also be susceptible to anxiety and panic attacks, as well as post-ICU syndrome, or PICS, a cluster of symptoms including generalized weakness, cognitive challenges, and poor mood.

Unlike medical post-traumatic stress disorder, which is also a concern for COVID-19 patients, PICS typically isn’t debilitating enough to reach a clinical level of depression or anxiety but can drain survivors and their family members for months or years, Craig Weinert, a pulmonologist and critical-care physician at the University of Minnesota who’s studied mental health outcomes of ICU patients, told Business Insider.

Any life-threatening illness that’s landed people in intensive care can lead to cognitive and psychological complications including delirium and PICS due to limited oxygen intake, sedative medication, and being in a strange environment where patients don’t know day from night.

But experts say aspects of COVID-19 are likely to make these consequences more prevalent, including the way it may infect the brain, the length of time on a ventilator, the heavy doses of sedative medications, and importantly, the physical isolation from family members during treatment.

“This is unprecedented – the inability to have family around you as you are experiencing and recovering from this severe illness,” Weinert said.