Flu season peaks with widespread cases in US but falls short of last season's intensity

Following a record-breaking flu season of 2017-18, this flu season is currently not showing the same type of intensity at its secondary peak.

According to the most recent week’s FluView report from the Centers for Disease Control and Prevention (CDC), seasonal influenza activity increased again the week ending Feb. 9, 2019, reaching a new season high.

The flu season typically peaks in February, a trend that this year seems to be following.

“It is not as bad a season as last year, but last year was quite a record-breaking season,” Dr. Bryan Lewis, research associate professor at the University of Virginia (UVA) Biocomplexity Institute & Initiative, said. “It’s widespread.”

The UVA Biocomplexity Institute & Initiative partners with AccuWeather to implement the tool that forecasts when and how hard the flu will strike a particular area.

The forecast will be updated weekly by using confirmed cases reported to the CDC, combined with data that model how people live, travel and commute; posts to social media made by sick people; and Google searches of flu symptoms and treatments.

“Currently, we’re having a secondary peak, so it looks like we’re going to have our usual pattern repeated,” Lewis said on Thursday, Feb. 14.

Only the Pacific Northwest and New England don’t exhibit this pattern of a secondary peak because they never fully peaked with the other regions at the close of 2018.

At the national level, this secondary peak has exceed the initial peak, along with four other regions: the South Central states, the mid-Atlantic, the Southeast and the Southwest.

Influenza activity is widespread in 48 states and Puerto Rico, and influenza-like illness (ILI) levels have reached 4.8 percent, according to the CDC’s FluView report.

For this week, the proportion of people seeing their health care provider for ILI increased from 4.3 percent to 4.8 percent, which is above the national baseline of 2.2 percent. This is the highest ILI has been this flu season.

This season is predominantly driven by influenza A(H1N1)pdm09 virus infections, but last season was predominately driven by the H3 subtype of the flu, which often causes more extreme cases that include mortality and hospitalizations.

“In terms of hospitalizations and mortality, in terms of people dying from pneumonia and influenza, it's lower than most seasons,” Lewis said. “We just haven't had that much H3; last season we had a lot of cases and a lot of people getting hospitalized and dying.”

However, overall intensity-wise, this season’s flu appears to be in the middle of the pack for most regions of the country, Lewis said.

Over the past five flu seasons, the peak percent of visits due to ILI has ranged between 3.6 percent in the 2015-16 season and 7.5 percent in the 2017-18 season. The highest percentage of ILI visits this season was 4.8 percent, recorded the week of Feb. 9.

Flu activity is similar to what has been seen during other H1N1-predominant seasons but remains well below what was observed last season.

Pneumonia and influenza fatalities are coming down from the last couple weeks, dropping to 6.9 percent of all deaths, below the seasonal threshold of 7.2 percent.

However, this week, another six flu-related pediatric deaths were reported to CDC, bringing the total to 34 flu-related deaths in children for the 2018-2019 flu season.

The highest hospitalization rate is among adults aged 65 years and older followed by children younger than 5 years and adults aged 50-64 years. This trend occurs during most seasons.

Hospitalizations from influenza continue to grow and remain lower than last year; however, its recent surges coupled with the proportion of H3 infections point to a potential increase in hospitalizations in the coming weeks.

The surveillance system that keeps track of flu data has recently changed things in a number of states this flu season. According to Lewis, this new surveillance system is throwing the data off, and some states may report higher-than-average numbers. Therefore, it's difficult to compare this season to previous seasons.

"We’ll just have to look back at it once the season is over to get a better feel," Lewis said.

The CDC expects flu activity to remain elevated for a number of weeks.

Lewis also said that he anticipates that there may be one or two weeks of increased intensity before it starts to decline.

“At the national level, there's already some regions of the country where things are sort of headed down and then there's other regions that are still climbing,” Lewis said.

Lewis forecasts that the flu season will stick around until the end of February, with potentially a few red states (where activity is high) around in early March.

Although controversial, the CDC, as well as Lewis, recommends the annual flu vaccine, as the best way to protect against influenza and its potentially serious complications. There are many benefits to vaccination, including reducing the risk of flu illness, doctor’s visits, hospitalization and even death in children.

Flu vaccination also has been shown to reduce severity of illness among people who get vaccinated but still get sick. For anyone 6 months or older who has not yet been vaccinated this season, CDC recommends that they get vaccinated now.

Other preventative measures include methods for boosting your immune system, so it is better able to battle the flu.

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