When most people think about deaths from influenza, elderly patients with underlying health conditions are likely the first to come to mind. But the complications of flu can also be fatal on rare occasions in children and young adults, even those who are otherwise healthy.
The U.S. has recorded 30 pediatric deaths from influenza so far this season, including a 10-year-old Connecticut boy who developed pneumonia and sepsis days after coming down with the flu. Nico Mallozzi, described by his mother in news reports as being healthy and as strong "as an ox," died in hospital Jan. 14.
A couple of weeks earlier, 21-year-old aspiring personal trainer Kyler Baughman of Pennsylvania died from septic shock after contracting the flu. The highly fit young man had not been vaccinated and initially ignored his symptoms, his parents reported.
In Canada, there had been fewer than five flu-related pediatric deaths as of Jan. 13, the latest week for which seasonal statistics are available. But 303 children under age 17 had been hospitalized for influenza, with 48 kids so sick they had to be admitted to the ICU, the Public Health Agency of Canada reported on its FluWatch website.
"It's tragic whenever there is a death due to influenza in a child," said Dr. Danuta Skowronski, an influenza expert at the BC Centre for Disease Control. "No question about it, it's heart-breaking.
"Fortunately it is a rare event," she said from Vancouver. "But that doesn't mean that deaths due to influenza in otherwise healthy people - including children - don't happen. They do. They're just rare."
There are a number of complications that can arise from infection with one of the influenza viruses circulating this season, with A/H3N2 and B/Yamagata being the dominant strains.
Pneumonia is among the most common, with either the influenza virus itself or a secondary bacterial infection taking up residence in the lungs, said Dr. Allison McGeer, director of infection control at Mount Sinai Hospital in Toronto.
In some cases, that lung infection can make its way into the bloodstream, causing what's known as sepsis. That infection of the blood can lead to septic shock, in which the body's organs shut down, causing death.
Flu can also severely exacerbate such chronic underlying medical conditions as asthma and cystic fibrosis in both children and adults, as well as chronic obstructive pulmonary disease (COPD) and congestive heart failure in older adults.
Infectious diseases specialists say children and adults with pre-existing health conditions who develop flu symptoms - including high fever, chills, body aches, extreme tiredness, cough and sore throat - should seek immediate medical care so they can be treated with an antiviral medication to reduce the risk of complications.
"We have a tendency to think that because influenza is so common and because almost all of the time you get it, you feel miserable for a few days and then you get better," said McGeer.
"That's our view of influenza and we don't recognize that there are a small number of catastrophically serious cases in children and young, otherwise healthy adults."
Still, both McGeer and Skowronski stress it's important not to overstate the risk of death in children and youth.
"Most otherwise healthy individuals are going to fully recover from influenza with no intervention," Skowronski said.
"We don't want to set off alarm bells. We need to put this into context."
For instance, a study that looked at pediatric flu deaths in the U.S. from 2004 to 2012 found 794 children under 18 died of influenza-related complications over the eight-year period, of which 453 (57 per cent) had underlying health conditions. Of the 341 children without high-risk conditions, 189 were aged five to 17.
Based on those findings, Skowronski calculated the risk of pediatric deaths from flu at about one in every two million children.
Yet at an individual level, some of these deaths may have been preventable with a simple shot in the arm, doctors suggest.
"The really hard part about influenza is that because it's so common, we don't take it seriously," said McGeer, adding that children and adults should get vaccinated against the flu - and that's especially critical for those with chronic medical conditions who are vulnerable to complications from the seasonal infection.
And while doctors concede that the effectiveness of the vaccine in preventing cases of influenza isn't ideal, it still can help reduce the severity of symptoms in those who contract the infection despite getting a shot.
One of the great ironies, said McGeer, is that it's easier to persuade people to get vaccinated against meningitis, a serious but very rare infection of the membranes around the brain and spinal cord, than it is against influenza.
"Young, healthy adults are actually more likely to die from influenza than from meningitis," she said. "But it's really hard to persuade them of that, because that's not how we see the disease.
And that's ... a great pity. Because if more people got vaccinated, people like me would not see as many people dying in our ICUs."