2019-2020 Weekly Influenza Update


2019 - 2020 Weekly Influenza Update: 9/29/2019 - 6/06/2020 (Week 40 - 23)
Fresno County Department of Public Health

The 2019 - 2020 influenza season began on 9/29/19 (week 40). This surveillance report monitors influenza activity and is updated weekly through the end of the 2019 - 2020 season. Providers must report laboratory-confirmed influenza-associated fatal pediatric cases in those 0-17 years old. Laboratory-confirmed influenza-associated deaths in those 18 years of age and older are voluntary reported by providers in California.1 Fresno County Public Health obtains the number of influenza-associated fatal cases between 0 and 17 years of age from investigations. The number of influenza-associated deaths in those 18 years and older are obtained from vital statistics records. Death and viral surveillance data for national and state regions is from the CDC’s FluView2 applications.

INFLUENZA DEATHS LOCAL, STATE AND NATIONAL

Fresno County: 9/29/2019 - 6/06/2020:3

  • Influenza-associated pediatric deaths (0-17 years old): 0
  • Influenza-associated adult deaths (18-64 years old): 9
  • Influenza-associated adult deaths (65 years or older): 20

California: 9/29/2019 - 6/06/2020:

  • All influenza-associated deaths: 881

Nationwide: 9/29/2019 - 6/06/2020:

  • Influenza-associated pediatric deaths (0-17 years old): 222
  • Influenza-associated adult deaths (18-64 years old): 3174
  • Influenza-associated adult deaths (65 years or older): 5653

INFLUENZA TYPING AT NATIONAL, REGIONAL, STATE AND LOCAL LEVELS

Figure 1 shows the cumulative distribution of influenza types from national, CDC Region 9 and California from 9/29/19 to 6/06/2020 (week 23). CDC Region 9 includes California, Arizona, Hawaii and Nevada.

 

Figure 2 shows the weekly distribution of influenza types from CDC Region 9 from 9/29/19 to 6/06/2020 (week 23). CDC Region 9 includes California, Arizona, Hawaii and Nevada.

Figure 3 shows the number of influenza positive tests by disease week and influenza type in Fresno County. The number of weekly samples changes throughout the season. The data for figure 3 comes from both public health and private laboratories. Most data for Fresno County comes from private laboratories where subtyping is not commonly performed.

Figure 4 shows the percentage of samples testing positive for influenza A or B by disease week in Fresno County. The number of weekly samples changes throughout the season.

INFLUENZA-LIKE-ILLNESS (ILI) AT EMERGENCY DEPARMENTS

Figure 5 shows the percent of ED visits attributed to influenza-like illness (ILI) in previous seasons and the current season. The baseline curve and alert thresholds are estimated using prior seasons’ data from 2014 to 2019. The baseline curve is the average expected percent of ED visits due to ILI. The alert curve is the upper 95% confidence limit based off percent ED visits due to ILI. The baseline and alert curves provide reference points to monitor ILI activity in the current season. Data on previous seasons and current seasons is collected through EpiCenter, a syndromic surveillance system.

CONCERN OVER COVID-19 INFECTION HAS PEOPLE SEEKING MEDICAL CARE IN THE ED. BECAUSE FLU AND COVID SYMPTOMS ARE SIMILAR, INFLUENZA ACTIVITY IS ELEVATED. THIS INCREASE IN ED ACTIVITY DOES NOT NECESSARILY MEAN FRESNO COUNTY IS SEEING AN INCREASE IN COVID-19 OR INFLUENZA INFECTIONS IN THE COMMUNITY. INSTEAD IT REFLECTS AN INCREASE IN FLU LIKE SYMPTOMS BEING REPORTED IN THE ED. PATIENTS PRESENTING WITH THESE SYMPTOMS STILL NEED TO BE EVALUATED BY A PHYSICIAN TO CONFIRM THE CAUSE OF THEIR SYMPTOMS.

 


  1. CDPH Recommendations for Influenza and Other Respiratory Virus Testing and Reporting - 2019-2020.

  2. CDC FluView.

  3. Fresno County counts include all influenza deaths that occurred within the county regardless of residence.