Tuesday, August 9, 2016

The Zika Pandemic: Mosquitoes and Climate Change

Climate change is a destructive force that is behind a host of civilization disrupting phenomenon and we can add the Zika virus and other mosquito born diseases to the list. The director of the WHO warned that Zika is "spreading explosively." Hot and humid weather associated with climate change is expanding the range of mosquitoes and the length of mosquito season. We have already established a link between climate change and diseases like malaria and Lyme Disease. Zika is also expected to increase in a world plagued by climate change. The Aedes aegypti is the type of mosquito that is the primary cause of Zika transmission, they thrive in temperatures above 50°F or at humidity levels above 42 percent. It is also believed that A. albopictus mosquitoes are also able to transmit Zika.

The three primary ways that Zika transmission will increase due to climate change have to do with heat and humidity. The heat (up to 95 F) increases the mosquitoes need for blood and therefore the number of people these mosquitoes will bite. Warm air also shortens the incubation period for the virus increasing the number of days that a mosquito can spread Zika. Mosquitoes do better in warmer climates and this enables them to expand their range northward.

While most people who contract the virus are asymptomatic, others can develop a fever, rash and joint pain. The real issue concerns pregnant women who are at increased risk of giving birth to Guillain-Barre syndrome which results in very serious neurological consequences that result in life long disabilities including paralysis. The most easily recognizable condition that has been linked to babies whose mothers have Zika is microcephaly, this condition causes a baby to be born with a much smaller head and smaller brains that have not developed correctly. There are currently a number of travel advisories warning pregnant women not to travel to infected areas.

According to research from Climate Central titled the States at Risk project, climate change is improving conditions for mosquitoes to thrive. The length of mosquito season is expanding in the US and this will also increase the incidence of mosquito born diseases. In many parts of the US ideal conditions for mosquitoes has increased by 40 percent compared to the 1980s. This means that mosquitoes are now a factor for an additional 40 days adding up to more than half the calendar year in cities like Baltimore, Maryland and Durham, North Carolina. A total of 20 US cities have ideal mosquito conditions for more than 200 days each year. More than three quarters of major cities in the US have seen mosquito season grow in the last three and a half decades.

Zika has been most closely identified with Brazil, Columbia and other South American countries. It is no coincidence that 2015 is the year that Zika exploded, it was also hottest year on record in South America. The Zika mosquito born virus is expanding into places that are becoming hotter and wetter than normal.

Zika is named for a forest in Uganda where it was first documented in 1947. It first appears in the medical literature in 1952. It is believed that it was introduced into Brazil in 2014 during the World Cup. It rose to prominence recently largely because it threatens those who are flocking to Brazil for the Olympics. Although Zika is now in at least 30 countries it has become a front page news issue because it now threatens Americans. The Centers for Disease Control and Prevention say that there are now more than 1,400 cases of Zika in the US. That is up from 591 cases at the end of May. The real numbers are actually much higher as most people display no symptoms. Most of the current wave of Zika cases are due to travelers returning from trips in South America. To make matters worse we now know that Zika can be transmitted through sexual contact. The Lancet published an article estimating that 200 million Americans are at risk from mosquito born Zika.

The cost of combating Zika is already high but it is soon to be exorbitant. To make way for the Olympics Brazil employed 200,000 military personnel to help educate the Brazilian people. Although the outbreak has just begun in the US, the White House has asked Congress for almost 2 billion to fight Zika in the US. To consider costs associated with dengue fever. As reported by Triple Pundit, Matheus Takatu Barros and Donald S. Shepard, PhD, from the Heller School for Social Policy and Management at Brandeis University, found that in Brazil fighting dengue cost, $728 million, and in India the price tag was $1.5 billion, in Indonesia it cost $2.2 billion and globally it was almost $9 billion.

The number of mosquitoes we see each year are growing and in many places the situation will worsen coming years as the climate changes. Models predict that average annual temperatures will rise along with heavier downpours, perfect conditions for mosquitoes to breed. Even with mitigation efforts it is all but certain that the number of Zika cases will continue to increase alongside other mosquito born illnesses including yellow fever, dengue fever and Chikungunya.

The Centers for Disease Control and Prevention (CDC) notes that "because the Aedes species mosquitoes that spread Zika virus are found throughout the world, it is likely that outbreaks will spread to new countries."

As quoted in Take Part, Peter Hotez, dean of the National School of Tropical Medicine at Baylor University in Houston expressed concern about, "the rapid spread" adding, "it’s alarming how quickly it’s going across all the Caribbean into Central America and Mexico." Many expect that Zika will spread to Southern Europe. The spread of Zika was referred to as "explosive" in the New England Journal of Medicine, noting that the pace of the "pandemic reemergence" of the virus is unprecedented. "I think we’re going to see this all over the western hemisphere except for Canada, the northern part of the U.S., and Chile, and the question is, where will it go next?" said Hotez.

In addition to pesticides and larvacides, GM mosquitoes are being used to interfere with the insect's reproduction. However, the increasing numbers of mosquitoes due to climate change mean that Zika is going to continue to be a serious health issue.

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