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With SARS, the world was somewhat lucky. Changing disinfectants in hospitals and elsewhere stopped the epidemic cold.

With Ebola we were fortunate in that vaccinations were in development, and given the urgency they were used and the epidemic stopped before it became a pandemic.

With Zika, what needs to be done is obvious. Will countries have the political will to do it? There are probably enough countries that can produce industrial quantities of DDT, so we may end up with countries that recognize the risks early enough to act, and countries where it becomes pandemic. Winters (Northern hemisphere now, Southern in a few months) will give countries far enough from the equator time to breathe, but as I see it, unless some magic bullet emerges quickly, Brazil and nearby countries will shortly be in a pandemic situation.

Technically, DDT is not banned in the US, but is restricted to public health emergencies. Zika certainly qualifies, and I expect states where local transmission occurs to respond with vigorous spraying. Note that uninfected mosquitoes are a good thing in areas where Zika is not epidemic, so spraying, in the US and other non-tropical countries should be restricted to areas where Zika transmission has occurred.

The other public health measure that can be done now is to confine patients with active Zika infections away from mosquitoes. Spraying walls and ceilings in those areas with DDT will help. One of the reasons why indoor spraying of DDT was and still is effective in reducing malaria cases is that mosquitoes avoid landing on DDT coated surfaces. Again, from an epidemic control point of view, reducing mosquito infections is much better than indiscriminately killing mosquitoes. Watch for court cases where infected patients object to confinement. Hopefully, the courts involved will recognize the importance of the public health measures. The precedents are there, including the case of Typhoid Mary.

DDT will not be a magic bullet. Since it hasn't been used for decades, a vigorous spraying compaign wherever Zika transmission pops up will certainly buy time. But spraying all of Brazil would be a huge undertaking even from the air--and the costs become much more of a logistics issue. Making that much DDT quickly is not going to happen. Converting existing chemical plants might work, but then there are the logistics of getting the DDT where it is needed, including a fleet of sprayer aircraft. (Incidentally, I am fairly certain that some reported DDT effects on humans were due to using kerosene or other hydrocarbons to dissolve the DDT for spraying. Hydrocarbons on standing water are toxic to mosquito eggs, so it seemed like a good idea. I think an alcohol, perhaps even ethanol, is a safer solvent.)

As I see it, all that spraying buys is time, maybe slowing the spread of the epidemic by a year globally, and more in temperate climates. Developing a vaccine is the long-term solution. How fast can it be done? The necessary steps are to isolate the virus, create an animal model for testing, identify proteins that can be attacked, and finally create a vaccine. In the normal FDA supervised progression, that plus validating the safety and effectiveness will take about two decades. But it needs to be done in two years or less.

I asked for this board to be created back when to discuss the economic effects of SARS. The biggest effect was on international air travel. That could happen again. The summer Olympics may also be a casualty this year. There will eventually be a drug company that wins the race to a vaccine. It is probably too early to start picking a winner in that race, or even to figure out who the competitors are. So as I see it the short term winner(s) will be chemical companies. There are no patents to worry about on DDT, so any chemical company will be able to manufacture and stockpile it.

The CDC Zika site can be found here: http://www.cdc.gov/zika/index.html
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