SYMVCD Sprays Sacramento in Spite of Zero Human Infections

•  July 30, 2010:  3 human cases in the state to date, 0 neuroinvasive cases, and 0 deaths.  SYMVCD sprayed Sacramento County anyway.
•  August 16, 2011:  12 human cases in the state to date, 0 neuroinvasive cases, and 0 deaths.  SYMVCD sprayed Sacramento County anyway.

    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 only a little greater rate than the yearly average, which is over 7000 for the whole state.  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" and emphasizing that that a "rational assessment of risk, then, hints that the hype about West Nile has been bigger than the threat."  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 took extreme action by spraying approximately 167,000 populated acres in South and North Sacramento – a grossly out-of-proportion response in light of the dramatically lower number of human infections to date that year.

    According to the California Department of Public Health, as of July 30, 2010, just prior to the spraying, there had been 3 human cases total in the state, none of which was neuroinvasive, and there had been 0 deaths of people in California with WNv in their system (the cause of death is often something other than WNv).  That was 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

    In 2011 SYMVCD sprayed 64,619 populated acres in Sacramento County, but the figures were still low this year -- WNv continues into chronic endemicity.  As of August 16, 2011, just prior to the spraying, there had been 13 human cases total reported in the state, and there had been 0 deaths of people in California with WNv in their system (again, the cause of death is often something other than WNv).  There had also been zero human cases in either Yolo County or Sacramento County, with no activity at all in Yolo County (no infected birds, no infected mosquito pools, no infected sentinel animals , no infected horses), according to the official state WNv website

    This ineffective and risky aerial spraying over populated areas was done at a cost of over $490,000 for the two years, as indicated by District officials.

    Nationally the figures are also 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:        629           57
2011:          32             3

These figures are available here.

    As is apparent from the state figures, there was a peak in California in 2005 with 880 total human cases and 19 deaths, 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 acknowledging the movement into chronic endemicity, 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 has been eradicated, but knowledgeable entomologists indicate that 1) such late outbreaks have never happened anywhere WNv has been, and 2) it is likely not possible to eradicate the virus.  Moreover, these entomologists tell us that 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 when there haven't been any to date in a region in a given season, 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.  The District Manager has told reporters the last two summers that it is important to spray to "break the transmission cycle."  We have asked what that means, but we have received no response.  We suspect that it is a feel-good public relations statement to divert attention from the fact that the spraying is being done for political and not health reasons.  We have also asked what the scientific evidence is that adulticiding breaks the transmission cycle, whatever it means.  These requests are in addition to our requests since 2005 for scientific evidence of the efficacy of adulticiding.  We have been offered none, and we are confident there is none.  It seems that the only way to actually "break the transmission cycle" would be to eradicate the virus, which is likely not possible. 

    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 responses last summer and this summer have highlighted these questions like never before.  The cost of over $490,000 is a nontrivial amount of tax money going to the purveyors and dispensers.  $490,000 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 8/31/11.