Border Influenza Surveillance Network of the Paso del Norte Region
The Border Influenza Surveillance Network of the Paso del Norte Region Southwestern New Mexico, Far West Texas, Northern Chihuahua 2012-2013 Summary
The BISN continued into the 2012-2013 influenza season with the following goals:
Promote real-time binational infectious disease surveillance
Enhance regional influenza surveillance capacity and reporting
Continue laboratory proficiency and communications on both sides of the border regarding influenza testing and results reporting
Develop capacity for responding to possible influenza pandemics
For this 2012-13 influenza season, there were 11 sites reporting to the BISN of the Paso del Norte Region:
5 sites in Southwestern New Mexico
6 sites in Northern Chihuahua
1 reference laboratory in El Paso County, West Texas
There were no sentinel surveillance sites from the West Texas region participating this season
The reporting standards are as follows:
- Continue the use of the Influenza-like Illness (ILI)/Enfermedad Tipo Influenza (ETI) clinical case definition of fever and cough and/or sore throat.
- Continue the weekly reporting of the number ILI/ETI cases (out of total number of patients) and any lab results, which includes rapid tests and laboratory specimens.
- The percentage of visits that were ILI/ETI positive will be reported for the entire Network as the level of activity occurring in the region.
- Continue the weekly compilation and distribution of BISN report, which would be the responsibility of the New Mexico BIDS officer.
The following two graphs show the ILI activity trends in the BISN for the entire 2012-2013 influenza season, for the time period October 6, 2012 through May 18, 2013. The first graph compares this year’s ILI activity to previous years’ influenza seasons, and the second demonstrates ILI activity for each Region within the network (Southern New Mexico and Chihuahua).
For the 2012-13 season, ILI activity reported in the BISN peaked at Week 49 (4%), with elevated activity occurring between weeks 48 (2%) through 52 (1.4%). Most of the higher activity was reported from the Northern Chihuahua sites, with a regional percentage of 4.8% at its peak, in Week 49. New Mexico sentinel sites reported higher ILI activity levels in Week 52, with a regional percentage of 2.2%, when the rest of New Mexico experienced a spike in activity across the State. New Mexico sentinel site activity increased further in Week 3 (2.3%) and peaked in Week 4 (3.1%), just as ILI activity was decreasing at the Northern Chihuahua sites.
The age groups that were most affected during the 2012-13 influenza in the BISN included those in the 5-24 years of age range (44% of all ILI cases) and those patients in the 0-4 years of age range (27%).
At each influenza sentinel site, clinicians are testing identified ILI patients with on-site rapid tests, or quick tests, that will produce results for influenza and the type within 10 minutes. Those ILI patients who undergo a rapid test, resulting positive or negative, are encouraged to have a second sample taken for laboratory confirmation. These specimens are generally sent to the state public health laboratory in the jurisdiction of each site. Influenza specimens are tested for the virus using the PCR technique, specifically the real time RT-PCR (reverse transcription – polymerase chain reaction), in most instances.
Note: Not all ILI-positive patients are tested with rapid tests or have a specimen collected for laboratory PCR confirmation.
* Rapid tests were conducted at the sentinel clinic site and results were reported the week the sample was taken
^ PCR tests were conducted in a laboratory setting and results were reported during the week they were confirmed, not necessarily the week the sample was collected. For the purposes of this graph, all attempts were made to count positive laboratory confirmed cases in the week that the specimens were collected.
The Virological Activity chart shows a trend that corresponds with the ILI activity charts (above) whereas activity and test positive rapid test results increased starting in Week 47 through Week 51, peaking in Week 49. The Northern Chihuahua sentinel sites combined reported 91 rapid test positive results (39%) for Type A and 74 rapid test positive results for Type B (32%), or 71% positivity for influenza out of all rapid tests conducted in the BISN for that week. In Week 50, positive rapid test results for Type B, mostly reported from Northern Chihuahua sites, peaked at 76 cases (36%), with 47% rapid tests resulting in Type A (22%), with 58% positivity for influenza (both types) out of all rapid tests conducted in the BISN. As for laboratory confirmed results in the BISN, Type A positivity peaked in Week 2, with 17 samples collected in that week resulting in Type A influenza. Type B influenza positivity peaked in Week 50 with five samples collected that week resulting in Type B.
The following graphs shows a breakdown of the total samples submitted for influenza type confirmation from the New Mexico BISN sentinel sites to the New Mexico public health state laboratory and from the reference laboratory in El Paso, Texas. The El Paso Department of Public Health conducts virologic surveillance through selected provider and hospital sites in El Paso County that submit samples when influenza is suspected.
Of the samples that tested positive for this influenza season, the dominating subtype was Influenza Type A H3 (73%) and the next predominant strain in circulation seemed to be Type B (18%). There were two samples submitted to the El Paso City Reference Laboratory that tested positive for both Influenza Type A and B. Only one sample from El Paso County tested positive for Influenza Type A 2009 H1N1.
Prepared by the New Mexico Office of Border Health
Border Infectious Disease Surveillance Program
Early Warning Infectious Disease Surveillance Program
For a summary on last season’s influenza activity (2010-2011), please click here for the presentation given at the BISN Evaluation Meeting in September 2011
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