US Flu Cases Reach 29 Million: Have We Hit Peak Season?

The US Centers for Disease Control and Prevention (CDC) estimates that there have been 29 million influenza cases in the United States in the 2019-20 season.

Influenza activity remains high, as it has been in recent weeks, but the latest flu data indicates that activity decreased slightly this week.

Overall, visits to clinicians for influenza-like-illness decreased from 6.7% last week to 6.1% this week. However, all US regions remain above baseline in reporting outpatient influenza-like-illness occurrence.

According to the latest FluView data, there have been 280,000 hospitalizations for influenza recorded as of February 15, 2020. This figure is consistent with hospitalization rates at this point in time during recent seasons; however, hospitalization rates among children and young adults are considered higher than in recent seasons.

The CDC also indicates that mortality related to pneumonia and influenza has been low during this respiratory virus season. So far, there have been 16,000 flu-related deaths documented during the US influenza season. Of these, there have been 105 influenza-associated deaths among children.

Earlier this season, Contagion® reported that influenza B/Victoria was the predominant strain in the US this season. At this point in time, there has been a decrease in the percentage of specimens testing positive for influenza B, although the percentage of specimens testing positive for influenza B is on the rise.

Nationally, influenza B viruses are being reported more commonly among children and young adults. Among young children aged 0-4, 53% of reported cases have been B viruses and among the 5- to 24-year-old population 68% of reported cases have been B viruses. On the other hand, A(H1N1)pdm09 viruses are the most commonly reported influenza viruses are the most commonly reported viruses among the 25- to 64-year-old population (57% of reported viruses) and 65+ population (64% of reported viruses).

The CDC continues to remind the public that antiviral medications are important to control the spread of seasonal flu. Thus far >99% of influenza viruses tested this season are susceptible to the 4 antiviral medications that are approved by the US Food and Drug Administration and that are recommended for use in the United States this season.

Last week, the CDC’s Morbidity and Mortality Weekly Report featured interim estimates of the effectiveness of 2019-20 flu shot. The report estimates that so far this season the vaccine is 45% effective overall and is 55% effective in children.

Although the authors of the report acknowledged that more effective vaccines are needed, they also noted that the currently available vaccines are providing substantial health benefits.

“It's important to know that this COVID-19 emergence is also occurring simultaneous to our regular seasonal influenza,” Christina Tan, MD, MPH, state epidemiologist, assistant commissioner, New Jersey Department of Health, told Contagion®. “What we're seeing in New Jersey, as well as elsewhere throughout the country, is peak activity of influenza right now. January, February is typically around the time that we see peak activity.”

So how can we fight flu in the wake of COVID-19’s emergence? Tan said that it’s important to take common-sense steps to prevent all respiratory viruses.

“This is an opportunity to remind everybody to be mindful that you know, if you haven't gotten your flu vaccine yet, get vaccinated for flu. Take those easy steps. Cover your coughs and sneezes, make sure you wash your hands all the time. Stay home when you're sick. Those types of precautions are helpful not only for seasonal flu, but also for whatever it might be emerging.”