November 8, 2021 | Week 43 | Volume 1 | Issue 17 |
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Welcome to the Florida Disease Activity Update, from the desk of Dr. Jonathan Day! It is Clarke’s privilege to share Dr. Day's weekly analysis of arbovirus disease activity in Florida with mosquito control professionals across the state. Our shared goal with Dr. Day is to provide timely and actionable information that mosquito control programs can use to make operational decisions and protect the public from vector-borne diseases.
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What's Ahead for this Newsletter?
Unless something very unusual happens, we are planning to publish two more weekly Newsletters in 2021: Issue 18 on 11/15/21 and Issue 19 on 11/22/21. We also plan to publish a Year-End Summary for the Florida 2021 Arboviral Transmission Season as Volume 1, Issue 20 on 1/5/22.
Looking ahead to 2022, the Newsletter will continue! In late May 2022, we will publish a Year in Review for 2021 where we will include information about malaria, Zika virus, and Chikungunya virus. We will resume weekly Newsletter updates for the 2022 arboviral transmission season in June. We continue to welcome your feedback and reader questions for future issues. Thank you for your readership and continued interest in this Newsletter!
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Darrin from Santa Rosa Beach, FL asks: “There have been six sentinel chicken seroconversions to SLEV in the Florida Panhandle during the past month. Should we be concerned?”
A: Probably not. Late season (October-December) sentinel chicken seroconversions are generally not predictive of high-risk human transmission events. There are three arboviral amplification periods in Florida, two minor and one major. The two minor amplification events coincide with spring (January-April) and fall (August-November) migrations when large numbers of susceptible migrating birds flood into Florida. These birds are sometimes trapped in Florida awaiting the proper environmental conditions that allow them to continue migration. During these periods, migrating birds can initiate local amplification foci where they infect mosquitoes. I suspect that such an autumn SLEV amplification focus has been established in Walton County. The major Florida amplification period coincides with the nesting season of resident birds (April-June). Sentinel chicken seroconversions reported between June and August are far more predictive of human transmission risk than are seroconversions reported during the autumn. Twenty sentinel chicken seroconversions in early July are far more troubling than 20 seroconversions in October.
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THE WEEK IN REVIEW:
ARBOVIRAL TRANSMISSION IN FLORIDA
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Low-level indicators of active EEEV, SLEV, and WNV transmission continued to appear in Florida during Week 43 of 2021, including:
- For EEEV, one positive equine and two EEEV antibody-positive sentinel chickens were reported.
- Two SLEV antibody-positive sentinel chickens and 14 WNV antibody-positive sentinels were also reported this week.
- One new travel-related DENV infection was reported this week.
West Nile continues to be the only mosquito-borne virus that currently threatens humans in Florida.
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WHAT ARE WE CURRENTLY SEEING? |
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Eastern Equine Encephalitis (EEEV) Activity
One (1) EEEV-positive equine (donkey) that was likely infected in mid-October was reported this week in Lake County. Two (2) EEEV antibody-positive sentinel chickens were also reported this week, both in Orange County. It is evident that there are still EEEV-infected mosquitoes present and active in Central Florida.
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Find a review of 2020 EEEV activity in the archived Vol 1, Issue 1 report.
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West Nile Virus (WNV) Activity
Fourteen (14) WNV antibody-positive sentinel chickens were reported during Week 43 in Alachua (2), Duval (1), Lee (2), Martin (1), Nassau (2), Sarasota (1), and Walton (5) Counties. This brings the total number of positive sentinel chickens reported in Florida during 2021 to 123. There is still active WNV transmission ongoing in Florida and the area of greatest concern for human transmission remains the central Florida Panhandle.
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Find a review of 2020 WNV activity in the archived Vol 1, Issue 1 report. |
Dengue (DENV) Activity
One (1) new travel-related dengue case was reported in Palm Beach County this week, bringing the total number of travel-related dengue cases reported in Florida during 2021 to 11.
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Find a review of 2020 DENV activity in the archived Vol 1, Issue 1 report.
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St. Louis Encephalitis Virus (SLEV) Activity
Two (2) new SLEV antibody-positive sentinel chickens were reported in Lee County during Week 43, bringing the total number of SLEV antibody-positive sentinel chickens reported in Florida during 2021 to 12.
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Find a review of 2020 SLEV activity in the archived Vol 1, Issue 1 report.
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OPERATIONAL STRATEGIES TO CONSIDER |
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Vector and arbovirus surveillance remains one of the most important tools that vector control agencies currently have at their disposal. Arboviral transmission indices (sentinel chickens, positive equines, positive exotics (i.e., emus), positive humans, and positive mosquito pools) provide indicators of local virus transmission, although sometimes not in a timely manner. Monitoring mosquito populations and their age structure provides added information about potential transmission risk. Additional vector control efforts in and around sites where virus transmission is known or suspected of recently occurring provides another potential mechanism to mitigate viral transmission.
The Florida regions with the highest current concern for arboviral transmission are those where indicators of EEEV transmission (sentinel chickens and EEE-positive equines) continue to be reported. These include all North Florida Counties and all of the Panhandle Counties, especially those around Walton County. In addition, the continued transmission of WNV to sentinel chickens in South Florida and in the Florida Panhandle indicates an ongoing risk of WNV transmission to equines and humans during the upcoming weeks.
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Jonathan Day, Professor Emeritus of Medical Entomology from the University of Florida, is a national expert on mosquitoes and other blood-feeding arthropods that transmit diseases to humans, domestic animals, and wildlife. In collaboration with other researchers, Dr. Day has developed an effective system for monitoring and predicting epidemics of mosquito-borne diseases.
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Acknowledgments: This analysis would not be possible without the tireless efforts of multiple agencies across Florida. At least 27 Florida agencies collect serum samples from sentinel chickens each week and mail them to the Florida Department of Health Tampa Branch Laboratory for analysis and reporting. Data are summarized by researchers at the Florida Department of Health in Tallahassee and reported weekly as the Florida Arbovirus Surveillance report.
Contributors to this summary and full report include: Andrea Morrison, PhD, MSPH, Rebecca Zimler, PhD, MPH, and Danielle Stanek, DVM, Florida Department of Health, Bureau of Epidemiology; Lea Heberlein-Larson, DrPH; Alexis LaCrue, PhD, MS; Maribel Castaneda, and Valerie Mock, BS, Florida Department of Health Bureau of Public Health Laboratories, and Carina Blackmore, DVM, PhD, FDOH Division of Disease Control and Health Protection. And, Dr. Rachel Lacey, Florida Department of Agriculture and Consumer Services, Animal Disease Diagnostic Laboratory in Kissimmee, FL.
Daily updates of the Keetch-Byram Drought Index (KBDI) are produced by the Florida Department of Agriculture and Consumer Services, Forest Service and are posted at: fireweather.fdacs.gov/wx/kbdi_4km.html.
All of the graphics used in this Newsletter were designed and developed by Gregory Ross.
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Clarke has been helping make communities more livable, safe and comfortable since 1946.
Learn more about our work in protecting public health on clarke.com.
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