1. The Movement of West Nile Virus in North America UC Berkeley October 1, 2003 Lyle R. Petersen, M.D., M.P.H.. Division of Vector-Borne Infectious Diseases Fort Collins, Colorado Photo of Cx. quinquefasciatus courtesy of Dr. Stephen Higgs, UTMB/Galveston

2. Order of Topics What is it? What is different now? How did it get here? How it is spreading? How big is the problem? What will happen next? How do we prevent it?

3. West Nile Virus: Background RNA virus Family Flaviviridae, Genus Flavivirus Member Japanese encephalitis serocomplex Closely related to SLE virus Isolation in 1937, West Nile district of Uganda

4. West Nile Virus: Approximate Geographic Range Before 1999

5. West Nile Virus Before and After Mid-1990s Before Mild self-limited febrile illness Central nervous system involvement rare Periodic outbreaks After Outbreaks associated with severe CNS illness Some outbreaks associated with avian mortality First recognition in North America (New York City) in 1999

6. West Nile Outbreaks Israel 1941, 1951-1954, 1957, 1980, 2000 France 1962, 2000 South Africa 1974 Romania 1996 Italy 1998 Russia 1999 United States 1999-2003

7. Arrival in North America

8. Madagascar Uganda 1937 Central African Republic 2 Egypt 1951 France 1962 South Africa 1974 NE United States Israel 98/99/2000 India Kunjin Romania 1996 Italy 1998 Volgograd 1999 1 LINEAGEClade Eg 101 U.S./Israel Europe/Russia India Kunjin Phylogenetic Tree of West Nile Viruses Israel 2000

9. An exotic arbovirus in NYC was surprising and unexpected: Should it have been?

10. International Animal Importations Into New York August 1998 – July 1999 N = 2,873,144 none 1 – 6000 6001 - 20000 20001 - 50000 50001 - 350000 350001 - Animals

11. Top Ten Countries of Origin Passengers arriving into NY Airports July 1998 – June 1999 N = 4,850,090

12. West Nile Virus Transmission Cycle Mosquito vector Incidental infections Bird reservoir hosts Incidental infections West Nile Virus West Nile Virus

13. Incidental hosts Humans Horses Other mammals Other mosquito vectors * Culex salinarius Cx.nigripalpus Ochlerotatus sollicitans Oc. taeniorhynchus Aedes vexans Ae albopictus * With possible epidemic potential ? ? Amplifying hosts Passerine birds Enzootic/epizootic (amplifying) vectors Culex pipiens Cx. restuans Cx. quinquefasciatus Cx. tarsalis West Nile Virus Amplification Cycle

15. West Nile Virus Ecology in North America, as of Fall 2003 43 mosquito species 170 native and captive avian species Mortality varies greatly by species Very high viremias in some species Bird-to-bird transmission documented Virus in feces and oral swabs Oral infection possible 18 other species (e.g., cats, dogs, squirrels, chipmunks, harbor seal, alligator, bats, reindeer)

16. WNV Surveillance Dead birds (especially crows) Human surveillance Mosquitoes Horse surveillance Live captive sentinels (e.g. chickens) Live wild birds Zoo animals

17. Reported to ArboNET as of 09/03/2003 Year# States# CountiesDate Range 19994289 AUG – 15 NOV 200012**1456 FEB – 17 NOV 200127**3598 APR – 26 DEC 200244**2,5313 JAN – 19 DEC 2003451,9541 JAN –29-SEP States and Counties Reporting WNV Activity, United States, 1999-2003* ** Plus D.C.

18. Reported WNV Disease Cases in Humans, United States, 1999-2003* * Reported as of 09/30/2003 Year# Cases# States# CountiesOnset Date Range 199962162 AUG – 24 SEP 20002131020 JUL – 27 SEP 200166103913 JUL – 7 DEC 20024,15639**74019 MAY – 19 DEC 20035,7224173028 MAR – 26 SEP ** Plus D.C.

26. Clinical Epidemiology Incubation period 2-14 days May be longer in immunosuppressed Approximately 20% mild febrile illness <1% severe neurological disease Meningitis, encephalitis, AFP Advanced age primary risk factor for encephalitis AFP patients may be younger Immunosuppressive drugs and hematological malignancies risk factors Approximate 10% mortality Long-term morbidity common

27. ~80% Asymptomatic ~20% “West Nile Fever” <1% CNS disease WNV Human Infection “Iceberg” in 2002 284 fatalities ~ 3300 severe disease ~400,000 asymptomatic ~100,000 mild illness

28. Human WNV Illnesses (n=4156), by Month of Symptom Onset, 2002 1 st Case May 19 Last Case Dec 19

29. Human WNV Meningoencephalitis Incidence, by Age Group, United States, 2002 * States with human cases

30. Fatality Rate among Persons with WNV Meningoencephalitis, by Age Group, United States, 2002

31. Human WNV Disease Cases, by Age Group and Clinical Category, United States, 2003* * Reported as of 09/03/2003

32. Novel Modes of West Nile Virus Transmission, 2002 Transplanted organs One donor to four recipients Transfused blood 23 confirmed cases in 2002, many more likely WNV screening began in July Breast milk One case, infant asymptomatic Transplacental transmission One case, severe outcome to infant Percutaneous, occupational exposure

33. St. Louis Encephalitis Related Japanese encephalitis serocomplex flavivirus Endemic in the Americas Similar maintenance vectors Birds are main hosts Causes human epidemics Is SLE a model for the future behavior of WNV?

34. Reported and Estimated Number of St. Louis Encephalitis Cases, U.S., 1932- Sept 12, 2003

35. Reported Number of West Nile Meningoencephalitis Cases, U.S., 1932- Sep 30, 2003

36. DC SLE 1975 DC WNME 2002* >=10 1 – 9.9 0 – 0.9 Incidence per 10 6 Reported Incidence in Humans: SLE 1975 vs. WNME 2002 * Reported as of 11/01/2002

37. West Nile Virus Future in the United States Worrisome for several reasons Prolonged transmission season Wide geographic range Many potential amplifying avian hosts High viremias in birds Many potential mosquito vectors Many potential human-biting mosquito species Persistent infections in areas over 5 years Urban / suburban / rural transmission

38. JOIN THE “SWAT TEAM” AGAINST WEST NILE VIRUS

39. Prevention Repellants DEET (up to 50% concentration); 10% in children Permethrin on clothing and fabrics Reduce mosquito breeding sites Long sleeves and pants Stay indoors when mosquitoes are biting (dawn and dusk) Bug zappers, sonic devices, CO 2 devices (mosquito magnet): no proven efficacy

41. Habitat elimination Larviciding Adulticiding