While it seems clear to me that the southeastern United States is about to experience an epidemic of chikungunya (the first two locally-transmitted cases occurred this week in Florida), what is unclear is its likely extent. The current epidemic in the Dominican Republic may provide some insight. Since chikungunya struck the Dominican Republic in early April, there have been almost 200,000 cases, an incidence rate of 20 per thousand for this nation of 10 million people.
If the Southeast, with a population approximately 80 million, had the same incidence rate as the Dominican Republic, we would expect 1.5 million cases in the first 100 days of an epidemic. However, due to widespread availability of insect repellent here and our stay-inside-the-air-conditioned-space lifestyles, our incidence rate is likely to be lower.
For the sake of argument, let’s assume our incidence rate will be 1/3 that of the Dominican Republic. This would translate to a half a million cases in the first hundred days, and we would then project approximately 10 million cases in the first year. With chikungunya’s fatality rate of 0.4%, an epidemic of this scale would kill 40,000, with fatalities being disproportionately among the very old and very young.
To put those 40,000 deaths in perspective, this is about the same number of annual deaths we see in the U.S. from each of the following causes: influenza, car accidents, suicides, and shootings. While we have become somewhat desensitized to deaths stemming from these familiar hazards, I anticipate that public reaction to an epidemic from a new and unfamiliar disease with a strange name will be something approaching widespread panic. Let me try to explain why.
First of all, nothing about the current level of function in either our state or federal government suggests that they could effectively coordinate either communications or logistics in a public health crisis. Now add to this the fact that a large portion of the public seems to have developed rather extreme anti-science views, for example the anti-vaccine and intelligent design communities. I think we can anticipate a fair number of non-productive conspiracy theories to arise from these factions and distract from addressing the problem.
Furthermore, I think we can also safety assume the epidemic will be politicized almost immediately. Given that chikungunya has reached Florida already, we can only be hours away from claims that this epidemic is President Obama’s fault and that the public is being put at risk by “liberals” who valued salamanders over humans by banning DDT. I expect calls for the return of DDT as well. (1)
So what can or should we do here locally to prepare for chikungunya? Epidemics are all about math. In this case the key variables are the number of currently infected people, the number of mosquitoes that can transmit the virus, and the number of mosquito bites. As time passes, a fourth variable, the number of people who are immune from having had chikungunya already, will become a factor.
We can collectively help to slow the spread of chikungunya by reducing the overall rate of mosquito bites in the county through common sense measures of which you are already aware; using bug repellent, wearing clothing the covers the body, minimizing pools of standing water near your home, and not going out at dusk and other times of day that mosquitoes are most active.
In addition, the Orange County Health Department should start making preparations. Cases of chikungunya will occur in geographic clusters. People who get the disease need anti-inflammatory and pain reducing medications as well as fluids to fend off dehydration.
Unfortunately, the United States is currently experiencing a shortage of sterile saline which is used to treat dehydration. In addition, if we had a cluster of cases in Orange County we could easily run out of hospital beds. We need to have a plan in place – and we may already have one – for a temporary clinic for hospital overflow, and we should work to build an inventory of saline solution. We also need a communications plan so that, at least here locally, people will have accurate information.