Flu Update

The worst flu season in years takes its toll on physicians and patients alike
By Cheryl England

THE 2017-2018 flu season is shaping up to be one of the worst in recent history. According to the Centers for Disease Control and Prevention (CDC), as of early February—the midpoint of flu season—nearly 60 hospitalizations for influenza occurred per 100,000 people in the United States. In contrast, at the peak of the 2014-15 season, one of the two most severe seasons in the last 15 years or so, 29.9 people out of every 100,000 were hospitalized for the flu.

The highest hospitalization rate during this influenza season is among people 65 years and older (263.6 per 100,000), followed by adults aged 50-64 years (63.1 per 100,000), and younger children aged 0-4 years (40.0 per 100,000). During most seasons, adults 65 years and older have the highest hospitalization rates, followed by children 0-4 years. This year, hospitalization rates are tracking higher than in any year since the CDC began monitoring that metric in 2010.

In addition, as of early February, the flu had caused a total of 63 pediatric deaths. The CDC has tracked pediatric deaths from influenza since 2004, and they’ve ranged from 37 to 171 during regular seasons; the highest was during the 2009 pandemic, when 358 pediatric deaths were reported. “We are receiving a volume of calls about the flu that we haven’t experienced in about ten years,” says Deborah Gulson, MD, a pediatrician at PediaTrust’s Lake Shore Pediatrics location. “The number of parents asking for flu services for their children is actually exceeding our capacity.”

Most Frequent Strains
The most frequently identified influenza virus subtype reported by public health laboratories to the CDC was influenza A(H3N2) virus. During the week ending Feb. 3, there were 1,453 influenza-positive tests reported. Of those, 73.3% (1,065) were influenza A viruses and 26.7% (388) were influenza B viruses. Of the 978 influenza A viruses that were subtyped, 85.3% (834) were H3N2 viruses and 14.7% (144) were (H1N1)pdm09 viruses. From Oct. 1 (when monitoring for this flu season began) through mid-January, more than 60,000 samples testing positive for influenza were reported.

“H3 and H2 strains of influenza are especially virulent,” says Dr. Gulson. “They have a history of causing severe symptoms and this particular H3N2 strain is causing more severe symptoms such as fevers and inflammation in airways. And, this strain has mutated since the vaccine for it was created, which is something influenza is very good at doing.” The flu vaccine is less effective against H3 viruses, which tend to cause more serious flu cases than other strains, according to the CDC.

The Flu in Chicago and Illinois
In Chicago, as of early February, the number of reported influenza-associated ICU hospitalizations had surpassed the total number of reported ICU hospitalizations for any season since 2010-2011. Since Oct. 1, 2017, 323 influenza-associated ICU hospitalizations had been reported; 297 were positive for influenza A, with 92 cases being the H3N2 strain, 13 cases being the H1N1 strain, and 192 cases consisting of an unknown subtype. Twenty-six cases were positive for influenza B. The median age of reported cases was 62 years. Two pediatric deaths were reported including one ICU hospitalization.

The number of influenza cases across the state of Illinois prompted state health officials in late December to recommend that hospitals limit visitors and put precautions into place aimed at preventing and controlling further spread of the flu. The precautions include restricting hospital visits for anyone younger than 18, limiting the number of visitors to two per patient, promoting hand washing and assessing visitors for symptoms of acute respiratory illness. Visitors who show signs of the flu should be asked to leave the facility or at the very least wear a sanitary mask.

Cook County public health officials have also instituted a screening policy at their hospitals to cut the risk of transmission to already ill people. Visitors are being screened for flu-like symptoms before being allowed to see patients. Children under 12 won’t be allowed to visit patients at Stroger or Provident Hospitals at all.

CDC Recommendations
The CDC continues to recommend the influenza vaccination for all persons 6 months of age and older as flu viruses are likely to continue circulating for weeks, and there is an increasing proportion of influenza B, H1N1, and H3N2 viruses being detected.

In addition, in the context of widespread influenza activity, the CDC is reminding clinicians and the public about the importance of prompt treatment with antiviral medications in people who are severely ill and people at high risk of serious flu complications who develop flu symptoms.

“As physicians, we have to just keep our chin up and work longer hours to get through the influenza season,” says Dr. Gulson. “And we don’t mind. Our ability to help others is our privilege.