SYMVCD Sprays Sacramento in Spite of Near-Zero Human Infection Rates

    We consider even a single death involving WNv to be tragic, and we urge people to take precautions from getting the virus, to educate others about the virus, and to be on the lookout for and dry up potential mosquito habitat.  Then, the first requirements of any public-health response to a potential disease such as West Nile disease are that it should be effective and involve less risk than that from the disease itself.  Unfortunately, aerial spraying is both ineffective and risky. 

    After the requirements of safety and efficacy we believe that a public-health response must be a proportional one.  For example, surely nobody would urge strict quarantines for all people in Sacramento and Yolo counties in a flu season in which deaths from flu and pneumonia were happening at a little greater rate than the yearly average, which is over 7000.  Instead, such measures as more education, greater availability of flu shots, etc., might be implemented.  In many situations, no action out of the ordinary would be taken, particularly in a year in which the number of flu and pneumonia deaths were on a rate toward a total well below the average of around 7000, unless there was solid evidence that an actual epidemic appeared to be imminent. 

    One very practical reason for a proportional public-health response is that money can help the public the most when it is spent in places where it can make the greatest difference.  We were reminded early of the extremely small relative risk from WNv, with articles such as this one from another state giving "a healthy dose of risk reality."  Indeed, one reason there is a vaccine for WNv for horses but not for humans is that the risk from taking a human vaccine would be greater than the risk from WNv.

    In the summer of 2010, however, SYMVCD has taken extreme action by spraying approximately 72,000 acres in South and North Sacramento – a grossly out-of-proportion response in light of the dramatically lower number of human infections this year.   This ineffective and risky application was done at a cost of over $450,000, as indicated in District records.

    According to the California Department of Public Health, as of July 30 there have been 3 human cases total in the state this year, none of which was neuroinvasive, and there have been 0 deaths of people in California with WNv in their system (the cause of death is often something other than WNv).  This is in contrast to 112 total cases with 4 deaths of people with WNv in their system in 2009, as well as 445 total cases and 15 deaths of people with WNv in their system in 2008.  The numbers since the virus entered the state are posted here.  There is now a clear downward trend from year to year as the virus recedes into chronic endemicity.

    Nationally the figures are equally striking.  Here are figures for the country since 1999, with the first number being the number of neuroinvasive cases and the second being the deaths of people with WNv in their system:

1999:         59              7
2000:         19              2
2001:         64            10
2002:      2946         284
2003:      2866         264
2004:      1142         100
2005:      1284         119
2006:      1459         177
2007:      1217         124
2008:        687           44
2009:        373           32
2010:         10              1

These figures are available here.

    As is apparent from both state and national figures, there was an early peak and then the virus began receding into chronic endemicity with a dampening sine wave (declining with some fluctuations), exactly what knowledgeable entomologists told us would happen.  Instead of recognizing the movement into chronic endemicity, or perhaps instead of even understanding how the virus evolves, vector-control officials tell us that WNv is "still in the area" and they therefore must spray.  The implication seems to be that if they don't spray we could have a major outbreak and they therefore must spray until WNv is gone, but knowledgeable entomologists indicate that such late outbreaks have never happened anywhere it has been.  Moreover, these entomologists tell us that the virus will likely never be gone and the spray has a negligible effect on transmission to humans anyway.  Viruses like this, such as those for Western Equine Encephalomyelitis and St. Louis Encephalitis, recede into chronic endemicity and we might have mild outbreaks every 20 years or so.  Those viruses are likely still in California, but no special actions are being taken, much less extreme ones. 

    How do vector-control officials justify their actions?  In addition to telling us that WNv is "still in the area" and they therefore must spray, they modify their "emergency aerial spray response" criteria to ignore human infections, and they then declare an "epidemic" based on the non-human parameters.  So, a metric that explicitly ignores the extremely low human infection rates is used to trigger when to spray, even though human infections are well below previous levels and are in a downward overall trend.

    Why are our public health and vector control officials failing the public in this way?  Is it because of the influence of money from the pesticide and chemical industries?  Is it because off-the-shelf and risky chemical treatments are easier to implement than the more-labor-intensive and safe biological controls?  Is it because highly visible actions will increase the sense of importance by the public of the District and assist with future funding?  Is it because the automatic reaction of some people is to treat problems with chemicals?  We have had similar questions in previous years, but the extremely out-of-proportion response this year has highlighted these questions like never before.  The over $450,000 cost of the recent spray is a nontrivial amount of tax money going to the purveyors and dispensers.  $450,000 could give significant support to a local program to produce and utilize Romanomermis culicivorax and Lagenidium giganteum instead of compounding previous lost opportunities for perfectly safe and effective biological control. 

    We note elsewhere on this page that the Nashville spray program was recently halted and spraying is not expected to be done in the future, precisely because spraying is ineffective.  Note the discussion as to how "it took six years and a new director for the Metro Public Health Department to finally use science, common sense, and their own records to make wise decisions."  Concerned citizens there are now urging their Health Department to create detailed protocols like those of many cities that do not spray, in order to "help avoid the protocol failures they had in the past."  Successes like this, along with the many cities that do not spray, give some hope that we might someday get sensible policy from our own public health and vector control officials.

Last update 8/22/10.