Ohio’s flu season was the worst in 5 years. Here’s why.

The number of influenza-related hospitalizations in Ohio this season was the highest in five years, according to the final state flu season data released Friday.

The figures were prompted by an early start, early peak and long season, officials said.

The 17,397 flu-related hospitalization cases reported for the 2017-18 flu season were more than twice as many as last season’s 8,661 cases reported by the Ohio Department of Health.

The severity of any flu season, which runs from early October through May, is difficult to predict, and it swings each year, said Sietske de Fijter, state epidemiologist.

“The only thing that’s predictable about the flu is that it is unpredictable,” de Fijter said.

Flu hospitalizations 
Ohio flu-related hospitalizations were high for the 2017-2018 season. 
  
  
SeasonOhio cases
2017-201817,397
2016-20178,661
2015-20163,691
2014-20159,374
2013-20143,489
Source: Ohio Department of Health 
 

RELATED: Ohio flu season winds down but still ‘widespread’

Public health officials mobilize each year to encourage vaccinations to slow the spread of the virus, which can lead to not only missed school or work but also death.

At its peak in January, there were more than 1,800 Ohio flu-related hospitalizations in one week. There were also four pediatric deaths this season related to the flu, including one child in Dayton.

De Fijter said this year the flu season started early, peaked earlier than usual and continued for a long season that led to high numbers of cases not only in Ohio but also around the U.S.

“What we did not anticipate and what we saw was the season started to peak early in the winter, and it went on for a long time. If I need to wrap it up with one word, it would be ‘long,’” she said.

High counts of flu-related hospital stays were reported around the country, officials said.

“The cases kind of went off the charts this year,” de Fijter said. “It’s just a national phenomenon this year.”

LOCAL: Area greenhouse that supplies large grocers preparing to open, hiring 30

The flu vaccine was about 36 percent effective this season, according to CDC’s early estimate reported in February. That is a higher effective rate than was feared after the Southern hemisphere, which experiences the flu season first, had a low vaccine effectiveness rate, de Fijter said.

However, even if someone is vaccinated and still gets the flu, they typically have milder symptoms than if they were unvaccinated.

A driver of the high rates of hospitalizations was the prevalence of the nasty H3N2 flu strain. The strain leads to higher rates of severe cases, and past years with high flu hospitalizations were also years when H3N2 was prevalent, said de Fijter.

Toward the end of the season, flu cases shifted from H3N2 to H1N1, which is a strain that typically causes less hospitalizations than the H3N2 strain.

The flu season prompted local hospitals to restrict children under the age of 14 and anyone with flu symptoms from visiting patients. Bryan Bucklew, president and CEO of the Greater Dayton Area Hospital Association, said the region's hospitals had not had to implement visitor restrictions for flu season in several years.

RELATED: What is the H3N2 flu and how bad is flu season this year?

“The number of hospitalizations was significantly above our five-year average,” Bucklew said.

Hospitals rescinded the restrictions in late March.

Bucklew said hospitals prepare for the season through hospital employees getting flu shots and preparing more beds than needed during slower periods.

He said some of the groups most impacted by the flu this year were the groups typically most susceptible, like older residents, children and those with compromised immune systems.

About the Author