There have been 18 deaths from a total of 515 laboratory-confirmed cases of the flu this season in Ottawa, but officials say the real number could be much higher. 

The deaths include 17 seniors over 70 and one younger adult, according to public health officials, who say that is "just the tip of the iceberg." 

"Not everyone gets tested for flu. So, yes, there could be more deaths...so we would expect there are more deaths out there where flu is likely a contributing factor," said Dr. Geneviève Cadieux, Ottawa's associate officer of health. 

Many of this winter's flu-related deaths are related to outbreaks at institutions like long-term care homes. 

Flu types behaving differently

Officials say this year there have been more cases of type B of the virus, which is unusual. Flu B usually peaks later in February and March and mostly affects children. Flu A usually starts affecting adults earlier in the season. This winter, health workers noticed something strange with both Flu A and B peaking around mid January. 

Last year at this same time, there were only 6 cases of flu B. This year there have already been 198 lab-confirmed cases, most of which are - in another anomaly - affecting seniors rather than children.

Changes to the way flu cases are tracked

The way health officials track the effects of different flu strains on the population is changing. There are questions about what impact those changes will have on the ability to track changing flu patterns. 

In the past, the Ministry of Health and Long Term Care would mandate and provide funding for local public health agencies to track and follow up with one out of every five lab-confirmed cases of flu. That would allow them to find out if the patient had been hospitalized or died. That data would help them extrapolate the total number of hospitalizations and deaths due to flu. They no longer have those numbers.

"They had identified an alternative way for us to be able to access this data, the problem is that the alternative way of accessing the data is not proving as timely as expected," said  Cadieux.

sneeze flu

Health officials in Ottawa have seen some unusual trends in this year's flu. (Uberphotos/Getty)

The ministry no longer mandates flu tracking. Instead it is moving to an online system of tracking flu cases, but there is a four to six week delay in publishing the results. Public health officials say the biggest impact of the change so far is that they can't point to the most recent numbers in their public messaging, when encouraging residents to get a flu shot. However, they can still access the data by contacting hospitals directly. 

If there is a silver lining to this year's flu season, it's this: according to Ottawa Public Health's latest information, flu activity this season seems to be slowing down. Despite that, officials are still reminding residents it's a good idea to get the flu shot.