# Presentation: 195616

## Meeting SummaryWest Nile Virus Conference2003

- New Orleans, LA

## Sage Advice on Dealing with the Press

- “Sitting around with a N95 mask on a tailgate of a pick-up truck with kids around doesn’t make good press”
- “Do it in your garage or where ever.  You don’t need to do it on your tailgate.”
- “Swab it in the bag and take it away so you don’t make a scene.”

## Sage Advice on Dealing with the Press

- “When it comes to West Nile, avoid denial”
- “Its just like a home pregnancy test.  You just get the results and bury them.”
- “It only costs 25 cents, what do you want?”

## Sage Advice for Surveillance 

- “Changing a case definition is like changing the constitution of a country.”
- “Do you think Jesse understands the case definition?”
- “Its nuts to stop testing after one bird.”
- “People were dropping birds at the health dept. and we were mapping it.”

## Sage Advice on Mosquito Surveillance and Control

- “We need the best bang for the public health buck.  We just can’t put out traps willy-nilly”
- “The Sherwin-Williams approach of covering the whole earth with insecticides just won’t work.”

## Critical Questions

- Do we sufficiently understand the virus and its transmission dynamics in nature to optimize  prevention of human infection?
- Can we predict human risk?
- Can we prevent human infection by urban vector control or other means?
- When epizootics or human cases occur, can emergency action prevent human infection?
- Can we optimally diagnose and treat human disease?

## Transmission dynamics

- Virus
- Birds
- Mosquitoes
- Humans
- Horses

## The Virus

- All strains >99.8% identical in USA
- Viral strain specific differences in viremia and mortality in birds (NY99>Kenya98>Kunjin)
- New stain (NY99) relates to frequency of severe neurological disease
- Virus may persist in some tissues/organs in some animals (humans?)

## Birds

- 162 species affected
- Substantial population reductions in some species
- Viremia up to 9-11 logs in some birds
- Blue jay, grackle, finch, Am. Crow, sparrow
- High viral levels in oral and cloacal swabs and feces
- Approx. 30% birds infected in epizootic areas; <1% in enzootic areas
- Novel transmission modes – importance?
- Bird-to-bird
- Oral

## Mosquitoes

- 37 infected species to date
*Cx. pipiens/restuans, Cx. quinquefasciatus*, *Cx. tarsalis* important enzootic vectors
- Potential competent bridge vectors
*Ae. albopictus, Ae. salinarius, Oc. japonicus*
- Vertical transmission may be important in some species
- Temperature dependence on extrinsic incubation period and disseminated infection
- Diverse overwintering mechanisms likely

## Ecological Factors in Transmission

- Virus exists in complex biologic systems in nature influenced by many factors.
- We cannot yet predict epizootics.
- Epizootics tend to be focal and develop quickly.
- Epizootics may portend future human infections
- Need to study ecological determinants of transmission.

## Horses

- Huge epizootic in mid-west
*Cx. tarsalis?*
- Low level viremias
- Equine vaccine now licensed, estimated 94% efficacy
- Other vaccines under development

## Humans

- >4000 cases
- 4 years of continued transmission in NY
- Viremia is low (generally <100 PFU/ml)
- May be prolonged in immunosuppressed
- Viral persistence in organs or tissues? Long-term sequalae?
- Novel transmission modes –
- Organ transplant and blood transfusion
- Intrauterine and breast milk – importance?
- Needlestick
- Protection from heterologous flavivirus exposure?

## Human Illness

- Age by far most important risk factor
- Immunosuppression?
- AFP syndrome
- Movement disorders very common
- Long-term clinical outcome poor?
- Costly: $5.5 million inpatient in LA
- No proven treatment

## Human Diagnostics

- MAC-ELISA best for clinical diagnosis
- Problem with secondary flavivirus infections
- NAAT insensitive for clinical diagnosis
- NAAT assays being developed for blood donor screening
- Sensitivity?

## Predicting Human Illness

- Single WNV dead bird predicts future human disease
- High sensitivity, low specificity
- Horses, sentinel chickens also predictive in some areas
- Quantifiable measures of epizootic activity seem to predict human disease
- WNV dead bird density, dead bird reports, MIRs, early WNV birds, etc. correlate with future risk
- Short lead time
- Differences in surveillance limit analysis
- Moving target?

## Preventing Human Illness

- Vaccine: no time soon
- Message tailored to different audiences
- Public, health care providers, political and community leaders
- Personal protection:
- Reasonable knowledge, little action
- Message tailored to different audiences
- Different audiences need different messengers
- Social marketing, sustained effort

## Preventing Human Illness

- Vaccine: no time soon
- Personal protection: reasonable knowledge, little action
- Mosquito control
- Does integrated pest management prevent human illness?  Need data.
- Emergency control:
- Sustained control effort resulted in dramatic decrease in densities of important vectors, but lack clear evidence of efficacy on reducing human illness
- How much, where, when, what triggers?
- Lawsuits galore
- ULV results in non-measurable exposure to humans

## Workgroup Summaries

## Surveillance Issues

- Add clinical syndromes with definitions
- Add new modes of transmission: *timliness!*
- Optional: extended variables
- “Opt-out” verification step
- Eliminate human and non-human, mammal denominator data
- Oral swabs for corvids, VecTest
- Need for some consistency?  Minimum surveillance?

## Laboratory Issues

- Biosafety levels: being reconsidered.
- No major changes in diagnostic schemes.
- Commercially produced reagents coming available
- Commercial EIA tests coming available.
- Interpretation: flavivirus positive.
- Neutralization: where, when, how (Chimerivax?)
- Problems with secondary infections.
- Spinal fluid important.

## Prevention and Control Issues

- Minimal mosquito abatement program capabilities
- Public education/communication program
- Mosquito abatement capability tailored to local resources
- Differences in opinion of methods for urban *Culex* control (e.g., container breeding)

## Prevention and Control Issues

- What personal prevention measures advocated in guidelines?  Need for simplicity of message in a way people can understand.
- How to produce behavior change?
- Long-term effort
- Use provider community
- Clear and consistent message
- Need to motivate, not just educate
- Target education dollars (e.g.,older persons, pregnant women?)

## Biology and Ecology Issues