The risk: Infecting Humans with the Zika virus using
The consequence: Other humans not yet infected with Zika virus
The vulnerability: Humans infected with Zika virus
The threat: Mosquito—specifically the Aedes aegypti and Aedes albopictus
The tactic: Infected blood ingested by mosquito and transmitted to uninfected human by subsequent mosquito bite
Just like an accident that is examined by its chain of events, risks can be considered in the same way. If you break a link in the chain, then the accident or risk can be prevented or contained. The risk of a Zika virus infection can be examined and controlled in a similar manner.
We want travelers at our airports. Aircraft operators purchase goods and services. Passengers and crews purchase goods and services, too. Banning or discouraging air traffic is counter-productive to the economy of an airport. Therefore, controlling a risk—especially a medical risk—is done best when it occurs beyond the traveler’s perception.
One problem with the spread of a virus like Zika is that four-out-of-five of those infected never experience any symptoms. Furthermore, customs agents can do everything right at an airport-of-entry and screen everyone properly, and travelers infected with Zika still go undetected. Passive monitoring of passenger and crew symptoms is a precaution that large airports have. However, smaller airports that are favored by general aviation do not always have this level of medical surveillance. So unless travelers from areas known to have a high risk of Zika virus transmission are quarantined or banned outright, this link is difficult to break. Let’s examine the next link.
Controlling the probability of an uninfected traveler being bitten by a mosquito is another link we might try to break. While it is possible to reduce the mosquito population in a closed space through the regular use of insecticides, this approach can become cost prohibitive quickly. Furthermore, many effective mosquito insecticides have the undesirable effect of making travelers uncomfortable or even sick. This result can lead to false positives for health surveillance and confound the efforts of health officials. Moderation is key when using insecticides in the arrival and departure halls as a last line of defense. So the consequence term in this risk equation is not likely a preferred link to attack.
Let's examine the threat itself, the mosquito. Understanding the Aedes mosquito's life cycle can help identify weaknesses to exploit. Standing water is where both types of the Zika-carrying Aedes mosquitos lay their eggs. According to sources in the World Health Organization and the U.S. Centers for Disease Control and Prevention, the Aedes aegypti mosquito prefers to lay its eggs in standing water that is dirty such as water collected in old discarded tires left outside in places where they catch the rain. The Aedes albopictus tends to prefer water collected on or around trees. The eggs can survive some eight months without water; however, water is required for the larvae to hatch. It is this one-to-two-week period as waterborne larvae that mosquitos are vulnerable to simple countermeasures. Breaking the Aedes mosquito life cycle can be as easy as flipping over containers of standing water at least once a week or treating sources of standing water too large to drain with Bti, or Bacillus thuringiensis israelensis. Bti attacks the digestive system of mosquito larvae but is harmless to humans and animals when used in accordance with manufacturer's recommendations.
Do these actions guarantee that there will be a zero probability of Zika virus transmission? No. However, you will stack the odds in your favor. With a reduced mosquito population from active efforts to remove sources of standing water and control larvae growth, the natural predators of the Aedes mosquito will help weaken or even break the risk chain. So be nice to those birds, bats, and dragonflies!
For more on the Zika virus and how to combat it within private and corporate aviation, read the upcoming edition of General Aviation Security.
Author: David Hook, General Aviation Security