Health officials are assessing whether the enterovirus D68 is linked to neurological symptoms, including muscle weakness, in several young patients who have been admitted to hospitals across North America.

In a release on Thursday, officials at McMaster Children’s Hospital in Hamilton, Ontario say one of four patients there tested positive for the virus.

They have been unable to pin down the cause of muscle weakness and are conducting further testing.

The symptoms are similar to those that have been reported in parts of Canada and the United States and since August, the virus has led to patients being hospitalized in both countries.

Public health officials in Canada and the United States are investigating potential links between polio-like symptoms and EV-D68 infections.

American officials now admit that four people have died and all had the virus.

The CDC is not releasing details about the latest victims, but one was a 10-year old girl from Rhode Island who contracted D68 and then a Staph infection in hospital.

All four had enterovirus D68 but it is unclear what role the virus played in their deaths.

In Calgary, four children were exhibiting symptoms similar to the virus and officials are waiting for lab results.

Doctors across the country have been told to be on the lookout for the virus.

Dr. Peter Niemen is a pediatrician and he compares the enterovirus to a chameleon saying that it doesn't always present itself the exact same way.

"The cases we tend to worry about more are immune compromised patients, maybe they're on steroids, or prone to catching infections, or of course asthmatics.  Those are the ones that need extra attention," said Niemen.

The challenge for doctors and infectious disease experts is that they don't know exactly why the symptoms are so wide and varied.

One theory is there could be co-infections; not just one virus but a couple simultaneously infecting patients.

According to experts this is a very normal year for the infections but what is different is the severity of the cases.

They say the vast majority of patients who contract the virus will either be asymptomatic or suffer only mild illness; however, a “small percentage” of patients will develop more severe symptoms.

(With files from Chris Epp and ctvnews.ca)