Doctors at the Alberta Children's Hospital are treating two children for meningococcal infection. (D'arcy Norman)

Doctors in Calgary are treating two children for meningococcal infection, a serious bacterial illness that can cause meningitis.

The two children, age 15 months and 4 years, respectively, aren't siblings but lived in the same Calgary house, health officials said Thursday afternoon.

One case is confirmed, and tests are pending for the other case, which is "highly suspicious."

"It's important for people to understand that while meningococcal infections are uncommon, these two cases by themselves do not constitute an outbreak," said Dr. Jim Kellner, an infectious disease specialist at the Alberta Children's Hospital in Calgary in a statement.

"That said, it is important that people do the most they can to protect themselves, particularly by ensuring their children have been properly and fully vaccinated. It also important for the public to be aware of the symptoms and signs of potential meningococcal infection."

People who lived with the children or visited their home are receiving preventive antibiotic treatment, and health officials are investigating whether others who came in contact with the residents will need to be treated.

Kellner wouldn't say where the children lived in the city of whether they had been vaccinated.

Boy died of meningitis earlier in the week

Health authorities said there is no evidence of a link between these two cases and the meningitis death of a seven-year-old Lethbridge boy on Monday night. There is also "no firm evidence" that the boy's illness was caused by meningococcus rather than another bacterium, a release from Alberta Health Services said.

Dr. Vanessa Maclean, the acting medical officer of health for the Chinook Health Region, said Wednesday that investigators weren't able to find the organism that caused the boy's illness.

"This is an isolated case," she said. "We have done our homework, and at this point, other than making people aware, there really is no other followup."

Meningococcal disease can be spread through close contact, such as coughing, sneezing or kissing.

An infection can cause sepsis, a serious infection of the blood and other parts of the body. It can also cause meningitis, the inflammation of the lining around the brain and spinal cord, which can be fatal.

Since 2002, Alberta has vaccinated children against three of the most common bacteria that cause meningitis, including meningococcus.

"While very effective, the vaccines do not protect against every strain of these three bacteria," the Alberta Health Services release said.

Alberta sees, on average, 20 cases of meningitis each year, of which about four are fatal.