Welcome to the 2018-2019 Influenza Season. Over the next several months, I will try to provide weekly updates on influenza’s passage across Wisconsin, enhanced by excellent surveillance data made available by the Wisconsin Division of Public Health, the Wisconsin State Laboratory of Hygiene, the Centers for Disease Control and Prevention, and the World Health Organization. I will make predictions based on trend data and my experience in reading the seasonal patterns of influenza. I will also provide some clinical guidance. Should you have any questions, please do not hesitate to contact me.
Wisconsin continues to have low, but increasing influenza activity at present. The majority of detections (63%) have been Influenza A[H1N1]. As of December 29, 2018, there had been 137 influenza-related hospitalizations since September 1, 2018; 49% of hospitalizations have been in individuals age ≥ 65 years. (As a point of reference, Wisconsin had tailed 1,328 hospital admissions at the same point last year).
The prevalence of influenza-like illness [fever of 100oF or higher and either cough or sore throat] in Wisconsin's primary care patients is 2.1% and is slowly rising.
11.2% of last week's primary care patients had all-cause respiratory infections.
The prevalence of acute diarrheal illness (ADI) in Wisconsin's primary care patients is at 1.7%; the most common pathogen is norovirus.
The most commonly identified viral causes of acute respiratory infections (ARI) in Wisconsin is parainfluenza. Over the past 4 weeks the typical ARI case presenting for primary care has been 35.5 years old and 71% of patients have been female. 60% of patients identified a sick contact 1-to-3 days before illness onset and typically present to the clinic 4.3 days after illness onset. 24% of illnesses are characterized as mild, with 71% having moderate symptoms and 2% having severe symptoms.
|Typical Symptoms||Percent||Viruses in Circulation||Percent|
Antivirals need to be started with 48 hours of symptom onset to be effective against influenza
Antivirals started after 48 hours may be effective for hospitalized patients with confirmed influenza
For the 2018-2019 season to date (last week):
Latest numbers as of 27 December 2018
Total cases: 627 (confirmed = 579, probable cases = 48)
Deaths: 382 (confirmed = 334, probable deaths = 48)
* The weekly influenza update is adapted from an email from Jon Temte, MD, PhD; Chair, Wisconsin Council on Immunization Practices; Professor, Department of Family Medicine and Community Health, University of Wisconsin School of Medicine and Public Health.