November 16, 2022 | Volume 2 | Issue 23 | As of Week 45
Welcome to the Florida Disease Activity Update from the desk of Dr. Jonathan Day.
It continues to be 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 public health from vector-borne diseases.

An archive of all past newsletter issues remains available on the Clarke website.
CONFESSIONS OF A MOSQUITO PRODUCER

Tale 1: My name is Jon, and I am a mosquito producer. This week, I'll share another of my experiences with the mosquito surveillance and control industry regarding my continued production of mosquitoes in my yard.

Source: A 2-gallon ceramic bird bath (Figure 1).

Production: Aedes albopictus.

Production Rate: About 20 adults per month.

The Larger Problem: Every yard in South Florida produces Aedes albopictus. This has been particularly problematic in 2022 because 679 travel-related dengue cases have been reported in Florida. Aedes albopictus is an aggressive day-feeding mosquito that is capable of acquiring and transmitting dengue virus. In addition, unlike Aedes aegypti, Ae. albopictus disperses considerable distances from its original breeding site. Travelers with an active dengue infection may infect and initiate a focus of locally-acquired dengue in any neighborhood in Florida.

Problem Solution: Dump the water in the bird bath once a week.
Figure 1. A 2-gallon ceramic bird bath that floods with every rain.
Figure 2. Solution to the mosquito-producing problem: dump and replace the water once a week.
THE CURRENT OUTLOOK FOR ARBOVIRAL TRANSMISSION IN FLORIDA DURING 2022

We are very close to the end of the 2022 arboviral transmission season in Florida. 
 
One new WNV human case was reported in Sarasota County last week. The individual was likely infected early in September. No new WNV-positive equines were reported last week. Twelve new WNV antibody-positive sentinel chickens were reported in Florida last week, bringing the total number of positive sentinels to 346 in 25 Florida Counties (Figure 3).
 
Two new EEEV antibody-positive sentinel chickens were reported in Lee and Orange Counties last week, bringing the total number of positive sentinels reported in 2022 to 66.
 
No new SLEV or HJV antibody-positive sentinel chickens were reported last week.
 
Three new travel-related malaria cases were reported last week in Miami-Dade (2 cases) and Pasco Counties, bringing the total number of travel-related malaria cases reported in Florida during 2022 to 49. For the 12-year period from 2010-2021, an annual average of 68 travel-related malaria was reported in Florida.
 
Three new locally-acquired dengue cases were reported last week in Miami-Dade County, bringing the total number of locally-acquired dengue cases in Florida to 41. All three individuals were likely infected in early October. We have passed the peak transmission period for locally-acquired dengue cases in Florida (Figure 4) and the worst of the 2022 dengue outbreak is likely behind us.
 
Fifteen new travel-related dengue cases were reported in Florida last week, bringing the total number of travel-related dengue cases reported during 2022 to 679 in 28 Counties (Figure 5). For the 12-year period from 2010-2021, an annual average of 105 travel-related and 16 locally-acquired dengue cases were reported in Florida. It is clear that we are well above average on both counts in 2022.
 
The risk of a significant outbreak of any mosquito-borne disease (dengue, EEEV, malaria, SLEV, or WNV) in Florida is currently low. However, it is important to remember that arboviral transmission risk in Florida is never zero.  
Figure 3. Sentinel chickens testing positive for antibody to WNV. Counties colored red indicate positive chickens reported during the 2022 arboviral transmission season. Counties colored blue indicate sentinel chicken seroconversions during the current reporting week (Week 45). Numbers indicate the total number of positive sentinel chickens reported in each county during 2022.
Figure 4. The temporal distribution of locally-acquired dengue cases in Florida by month of onset for cases reported in 2009 through 11/12/2922.
Figure 5. Travel-related dengue cases in Florida during 2022. Counties colored blue indicate travel-related dengue cases reported during 2022. Counties colored red indicate travel-related dengue cases reported during last week (Week 45). Numbers indicate the total number of travel-related dengue cases reported in each county during 2022.
Year to Date Summary of Mosquito-Borne Disease Transmission

As of Week 45. 2022, the following mosquito-borne disease transmission events and pathogen introductions have been reported in Florida:
Table 1. Summary of mosquito-borne disease transmission and travel-related cases in Florida as of November 12, 2022.
We have passed the point in the 2022 Florida arboviral transmission season when there is the risk of a significant arboviral outbreak anywhere in the state. Transmission of WNV has started to decline (Figure 3) and new reports of human and equine WN cases are for infections that are more than a month old. Travel-related and locally-acquired dengue cases are beginning to decline (Figures 4 and 5). In all likelihood, the information presented in Table 1 will be a reasonably accurate summary of the 2022 Florida arboviral transmission season. 
OPERATIONAL STRATEGIES TO CONSIDER
Vector and arboviral surveillance remain some of the most important tools that vector control agencies currently have at their disposal. Arboviral transmission indices (sentinel chickens, positive equines, positive exotics such as 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 gives additional information about potential transmission risks. Supplemental vector control efforts in and around sites where virus transmission is known or suspected of recently occurring provide another mechanism to mitigate viral transmission. 
 
Specific operational strategies will be discussed during the 2022 arboviral transmission season depending on where and when vector-borne disease transmission becomes obvious in Florida.
 
  • There is currently a low risk of EEEV transmission in Florida.

  • There is currently an extremely low risk of SLEV transmission in Florida.
 
  • There is currently a low risk of a significant outbreak of WNV transmission in Florida. 
 
  • There is currently a low risk of a significant outbreak of locally-acquired dengue in Florida.
 
  • There is currently an extremely low risk of an outbreak of locally-acquired human malaria in Florida.
ABOUT DR. JONATHAN DAY
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.
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, compilation 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.

All of the graphics used in issues of this Newsletter are designed and developed by Gregory Ross.
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