Westchester County Department of Health Community Health Assessment Data Update 2018.01 @wchealthdept Arbovirus/Mosquito Control and Surveillance, 1999-2017 In this issue: Mosquito Surveillance Trap Sites, 2017 Mosquito Control and Surveillance in Westchester - About the program - Catch-basin evaluation and larviciding - Mosquito trapping and mapping West Nile virus Zika virus Other Mosquito-borne Diseases Minimizing your Risk for Mosquito-borne Disease Jiali Li, Ph.D. Director of Research & Evaluation Planning & Evaluation Renee Recchia, MPH Acting Deputy Commissioner of Administration Project Staff: Junaid Maqsood, MPH Medical Data Analyst George Latimer, Westchester County Executive Sherlita Amler, MD, Commissioner of Health Mosquito Control and Surveillance The Westchester County Department of Health (WCDH) has worked since 1999 to prevent the spread of arboviruses which cause mosquito-borne disease. This has been done through mosquito control and education efforts. Mosquito Control Eliminating Breeding Sites Each spring and throughout the mosquito breeding season, WCDH collaborates with municipalities, community stakeholders, and the public to identify and eliminate standing water in places such as empty lots and backyards. These intensive efforts reduce potential mosquito breeding sites. The health department also investigates any complaints of standing water from residents. Minnow Distribution Fathead minnows help provide control by eating mosquito larvae and pupae before they emerge into adult mosquitoes. Since 2013, WCDH has distributed minnows to County residents and municipalities. Approximately 410 pounds and 450 pounds were distributed in 2016 and 2017, respectively. Larvicide Catch basins are municipal drainage systems used to move excess rainwater from streets and other urban surfaces into the storm drain system. Catch basins may hold standing water for a long period of time, making them ideal for mosquito breeding. Up to 2017, WCDH evaluated thousands of catch basins throughout the County and applied larvicide when necessary in each May. Starting in 2018, WCDH will larvicide as needed. Adulticide If disease-bearing mosquitoes ever become a serious threat to public health, the county will consider applying pesticides. To date, this has only occurred in 2000. Mosquito Surveillance Trapping Each year, WCDH sets up multiple trap sites throughout the County from May to October. The trapping of mosquitoes allows for surveillance and testing for the presence of mosquito-borne diseases. Trap sites are selected based on population density, where positive mosquitoes have been identified in the past, and locations of past human West Nile virus (WNV) cases, as well as site availability or the need for additional surveillance in response to heavy mosquito infestation. In 2016, WCDH expanded the number and type of traps due to the new threat of potential spread of Zika. Testing WCDH staff collects the trapped mosquitoes three to four times a week. The trapped mosquitoes are sorted by species and submitted in batches for WNV, Zika virus (beginning in 2016), and other arbovirus testing at the NYS Wadsworth Laboratory following the NYSDOH guidelines. 2 Catch Basin Evaluation and Treatment Number of Catch Basins Evaluated and Treated with Larvicide, 2002-2017 80,000 Evaluated Treated 69,286 69,252 70,000 67,228 66,818 65,758 65,455 65,151 63,969 62,740 59,530 60,483 60,000 57,778 57,742 57,884 57,207 57,990 56,137 55,100 53,857 54,756 54,204 53,524 51,507 52,886 50,647 50,000 41,629 42,355 42,534 42,630 40,227 40,000 38,234 33,999 30,000 20,000 10,000 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011* 2012 2013 2014 2015 2016 2017 *From 2011 on, WCDH no longer carried out larvicide activities on NYSDOT roads. Average Percentage of Evaluated Catch Basins Treated with Larvicide, 2002-2017 On average, approximately 4 out of 5 catch basins evaluated in Westchester County were treated with larvicide between 2002 and 2017. Some catch basins were not treated 79.2% either due to the 20.8% absence of standing- water or inaccessibility. 3 Mosquito Surveillance Total Number of Mosquitoes Trapped, 2001-2017 49,895 50,000 45,000 40,000 35,000 31,644 30,000 26,971 24,195 25,000 21,912 20,114 20,668 20,000 17,991 17,454 18,468 15,000 11,922 11,037 10,087 10,827 10,200 11,140 10,000 7,952 5,000 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014* 2015 2016 2017 *2014 data for number of mosquitoes trapped is an estimate Average Number of Mosquitoes Trapped per Epidemiological Week, 2001-2017* 2,000 1,787 1,800 1,660 1,594 1,600 1,438 1,400 1,238 1,194 1,147 1,164 1,190 1,200 1,068 985 913 1,000 845 858 874 781 800 684 632 630 600 457 400 323 200 127 74 9 0 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 May June July August September October Epidemiological Week *Data for 2014 are incomplete and thus not included An epidemiological week (also known as epi week, CDC week, or MMWR week) is a standardized method of counting weeks that allows comparison of data by year. Each epidemiological week starts on a Sunday with the first one being the first week with at least four days in the calendar year. Therefore, the starting date of each epidemiological week may fall on a different date each year. For example, the first epidemiological weeks started on 12/31/2000 for 2001 and started on 1/2/2017 for 2017. The start of the 20 th epidemiological week ranges from 5/11 to 5/17 in any given year and the start of the 43rd epidemiological week ranges from 10/19 to 10/26. 4 Mosquito Batches Submitted for Testing and Results Number of Mosquito Batches Submitted for Testing and Batches Testing Positive for West Nile Virus (WNV) by Year of Collection, 2001-2017 900 803 800 742 721 716 Batches Submitted WNV+ Batches 700 652 628 600 572 500 410 420 380 400 378 337 300 263 235 242 214 215 200 67 100 45 24 32 29 7 15 0 2 12 6 13 7 6 17 3 5 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Cumulative Number of Batches Testing Positive for West Nile Virus by Epidemiological Week of Collection, 2001-2017 80 68 70 60 50 40 36 32 30 30 27 22 18 19 20 17 7 10 4 6 1 0 1 1 1 0 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 June July August September October Epidemiological Week Since 2001, 7,928 mosquito batches have been submitted for testing. Each batch contained a minimum of 10 mosquitoes. Overall, 290 batches were tested positive for WNV, with the positive rate of 3.7%. During the past 17 years of surveillance, the greatest number of WNV positive mosquitoes was found in the 34th week of the year (typically mid- to late-August). No positive batches were identified before week 25 or after week 41. No Zika virus has been identified in any mosquito batches to date. 5 West Nile Virus WNV can cause serious illnesses. Symptoms of West Nile Virus Approximately 3 out of 4 people who are infected do not show any symptoms, but Mild symptoms: about 1 in 4 will develop mild symptoms Body aches Headache 3-14 days after being bitten by an infected Fever Mild rash mosquito. Fatigue Swollen lymph glands Even though the chance of serious disease is Serious disease symptoms: less than 1%, there is no treatment or vaccine. Serious symptoms may last for several weeks High fever with rapid onset Encephalitis and can be life-threatening among people Headache and neck stiffness Paralysis Disorientation Coma with a vulnerable immune system. The Convulsions Death neurological effects of a WNV infection may be permanent. The West Nile Virus Life Cycle West Nile virus is reproduced by a cycle of transmission between adult blood-feeding mosquitos and birds, which are the main reservoir hosts for the virus. Certain species of mosquitoes feed on both birds and mammals, and are the bridge vector for WNV transmission to humans. In Westchester County, the Culex, Ochlerotatus, and Aedes genera are the most common mosquito types. The species Culex pipiens- restuans is the major mosquito vector for WNV transmission between animal reservoirs and humans in New York State. 6 Trap Site Locations and West Nile Virus Human Cases Over Time Cumulative Distribution of Mosquito Trap Sites and West Nile Virus (WNV) Human Cases, 1999-2017* *Mosquito trap site data presented for 2001-2017 only. **Human cases include both confirmed and probable cases. 7 West Nile Virus Human Cases Number of Confirmed West Nile Virus Human Cases, 1999-2017 10 9 9 8 7 6 5 4 4 4 4 3 3 3 3 3 2 2 2 2 2 2 1 1 1 0 0 0 0 0 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 The health department monitors West Nile virus encephalitis among other mosquito-borne diseases. From May to October, the health department provides all county hospitals and infectious disease specialists with educational materials, reminders on criteria for case reporting and submission of laboratory specimens, and updates on arbovirus activity. Health department staff visit the homes and surrounding neighborhood of every person who is confirmed to have West Nile virus to identify and eliminate any mosquito breeding areas.