After months of anticipation, the Zika virus has finally arrived to the continental U.S., with 15 non-travel cases being reported in Florida as of August 2. The virus is carried primarily by a species of mosquito called Aedes aegypti.
The Centers for Disease Control (CDC) issued its first-ever warning for within the U.S., urging pregnant women to avoid travel to a Miami neighborhood where the Zika investigation is centered.
CDC and the Florida Health Department recommended an aerial spraying program to cover a 10-square-mile area just north of downtown Miami.
The state is spraying a chemical called Naled, which is an organophospate pesticide that causes severe skin and eye irritation; it also contains an inert ingredient called napthaline which is classified by the EPA as a “possible human carcinogen.”
When this chemical was recommended to be sprayed in Puerto Rico, protests erupted from residents concerned about their health and the environmental impacts.
Organophosphate pesticides also devastate bee populations and other beneficial insects, which affects agriculture as well as ecosystem health.
Governments are often quick to pour chemicals into the environment as a first reaction, as it gives the appearance of “doing something” and enriches chemical companies who contribute to political campaigns. So, with 15 cases of Zika and sustained media fear-mongering, the first government-sponsored spraying program has begun in Florida.
According to the CDC, for most people the Zika virus causes mild symptoms of fever, rash, joint pain, red eyes, muscle pain and headache that last up to a week. Many patients don’t even know they have it, as it is like symptoms of other common sicknesses. Hospital visits are rare, and death very rare.
The bigger fear is the purported link between Zika virus in pregnant women and microcephaly in the baby. However, aswe reported on July 2, the only country experiencing an abnormally high rate of microcephaly is Brazil, where doctors insist that a larvacide called pyriproxyfen could be a factor in microcephaly.
Colombia is also experiencing a Zika virus outbreak, but there is no connection between Zika virus and microcephaly in that country.
Of the nearly 12,000 pregnant women with clinical symptoms of Zika infections until March 28, no cases of microcephaly were reported as of May 2.
Five new cases of microcephaly with Zika infections were found prior to June 18 in Colombia; however, this is still consistent with the random co-occurrence of each of the separate conditions.
Back in Brazil, the expected “explosion” of cases where brain defects are linked to Zika virus has not occurred. Defying predictions, most of the cases have remained clustered in the northeast region, which has caused Brazil to open a probe into the possibility of co-factors such as other viruses or environmental factors.
The story of Zika-carrying mosquitoes gets even more interesting when we delve into history. And, perhaps unsurprisingly, the U.S. military is involved.
An investigation by Sarah Laskow at Atlas Obscura found that in the 1950s, the U.S. was seeking to weaponize the Aedes aegypti mosquito while Brazil and other Latin American countries were trying to eradicate it.
Zika — Click on Document here.
Strain: MR 766 (Original) Classification: Flaviviridae, Flavivirus Original Source: Blood from experimental forest sentinel rhesus monkey, Uganda, 1947 Depositor: J. Casals, Rockefeller Foundation
At Fort Detrick, the military’s biological weapons base in Maryland, in great secret, Army scientists were considering how fleas, grasshoppers, and mosquitoes might be deployed against the Communist threat. These insects were harder to protect against than gas— masks wouldn’t help. The threat they posed would last, as long as a population of insects remained alive. Plus, it would be very difficult to pin an insect-borne attack on the U.S.
Among these possible insect soldiers, A. aegypti was “the golden child,” writes Jeffrey A. Lockwood, in Six-Legged Soldiers, because the disease it carried, yellow fever was so terrible. The Army Chemical Corps, in a 1959 report, notes that yellow fever is “highly dangerous” and that “since 1900, one-third of patients have died.” There were parts of the Soviet Union that had never been exposed to the disease, which made them vulnerable, but which had the right climate to support mosquitoes. The Chemical Corps started to experiment with how a brigade of A. aegypti might be deployed and what sort of damage they might do.
Concerted efforts began around 1900 to tackle the deadly problem of yellow fever, which was afflicting American troops carrying out imperialistic adventures in the Caribbean. After discovering that the mosquito caused yellow fever, Americans led a successful eradication program in Cuba.
American scientists took their methods to Brazil, where Fred Soper – with the help of the authoritarian Brazilian regime – implemented a strict A. aegypti eradication program that succeeded in eight cities in northern Brazil.
In 1947, the year Zika was discovered, he had convinced enough people that eradication was possible that a consortium of American countries endorsed a plan to rid the entire hemisphere of the mosquito.
Most of the countries succeeded. By 1962, there were no A. aegypti to be found in 18 continental countries and a number of Caribbean islands. Only a few hold outs had failed to start programs to destroy these mosquitos. The one that made Soper the most frustrated was his own.
When the U.S. Public Health Service finally began A. aegypti eradication efforts in the Southeast to combat yellow fever, the military was simultaneously studying their use as biological weapons against Communist countries.
As part of this research, Army scientists had to see how quickly A. aegypti populations spread through populations, so they released hordes of mosquitoes (uninfected by yellow fever) in American cities like Savannah, Georgia and Avon Park, Florida.
They would load hundreds of thousands of mosquitos into planes and, later, helicopters, then drop them over the field and see how far they could spread.
The mosquitoes apparently performed well enough: By 1960, the Chemical Corps was producing 500,000 A. aegypti every month, rearing them on sugar water and blood and letting them lay their eggs on paper towels. Scientists had found they could infect a new generation of mosquitoes with yellow fever by mixing the virus in the solution in which the mosquito eggs grew. Hundreds of thousands of mosquitoes were not enough to start a real epidemic, though. The corps proposed constructing a facility in Arkansas that could produce 100 million A. aegypti mosquitoes each week.
In the same years, federal government was attempting to eradicate A. aegypti, the military was releasing countless numbers of the mosquitoes into the environment.
Yellow fever was not so much of a problem in the U.S. as it was in tropical regions, and the same authoritarian methods employed in places like Brazil could not be applied in the United States. Funding and enthusiasm was also a problem, and it was becoming realized that true eradication was a pipe dream.
After being beaten back for a few decades, A. aegypti has now invaded more territory than it ever inhabited before. And scientists now say the species may be “more sophisticated, individually complex, and formidable than anyone imagined.”
Of course, we can’t blame the American military for the spread of the mosquito species largely responsible for the Zika virus and yellow fever, but the secret history tells us much about how these sorts of things are viewed by government.
Even as the world was battling against infectious disease, the military saw an opportunity to find more effective ways at killing people. And it used its own citizens as unknowing subjects for research.
Where did Zika virus come from and why is it a problem in Brazil?
January 27, 2016 9.48pm AEDT The Conversation
The suspected culprit is a mosquito-borne virus called Zika. Officials in Colombia, Ecuador, El Salvador and Jamaica have suggested that women delay becoming pregnant. And the Centers for Disease Control and Prevention has advised pregnant women to postpone travel to countries where Zika is active.
Zika virus was discovered almost 70 years ago, but wasn’t associated with outbreaks until 2007. So how did this formerly obscure virus wind up causing so much trouble in Brazil and other nations in South America?
Where did Zika come from?
Zika virus was first detected in Zika Forest in Uganda in 1947 in a rhesus monkey, and again in 1948 in the mosquito Aedes africanus, which is the forest relative of Aedes aegypti. Aedes aegypti and Aedes albopictus can both spread Zika.
Sexual transmission between people has also been reported.
Zika has a lot in common with dengue and chikungunya, another emergent virus. All three originated from West and central Africa and Southeast Asia, but have recently expanded their range to include much of the tropics and subtropics globally. And they are all spread by the same species of mosquitoes.
Until 2007 very few cases of Zika in humans were reported. Then an outbreak occurred on Yap Island of Micronesia, infecting approximately 75 percent of the population. Six years later, the virus appeared in French Polynesia, along with outbreaks of dengue and chikungunya viruses.
How did Zika get to the Americas?
Genetic analysis of the virus revealed that the strain in Brazil was most similar to one that had been circulating in the Pacific.
Brazil had been on alert for an introduction of a new virus following the 2014 FIFA World Cup, because the event concentrated people from all over the world. However, no Pacific island nation with Zika transmission had competed at this event, making it less likely to be the source.
There is another theory that Zika virus may have been introduced following an international canoe event held in Rio de Janeiro in August of 2014, which hosted competitors from various Pacific islands.
Another possible route of introduction was overland from Chile, since that country had detected a case of Zika disease in a returning traveler from Easter Island.
Most people with Zika don’t know they have it
According to research after the Yap Island outbreak, the vast majority of people (80 percent) infected with Zika virus will never know it – they do not develop any symptoms at all. A minority who do become ill tend to have fever, rash, joint pains, red eyes, headache and muscle pain lasting up to a week. And no deaths had been reported.
In early 2015, Brazilian public health officials sounded the alert that Zika virus had been detected in patients with fevers in northeast Brazil. Then there was a similar uptick in the number of cases of Guillain-Barré in Brazil and El Salvador. And in late 2015 in Brazil, cases of microcephaly started to emerge.
How Zika might affect the brain is unclear, but a study from the 1970s revealed that the virus could replicate in neurons of young mice, causing neuronal destruction. Recent genetic analyses suggest that strains of Zika virus may be undergoing mutations, possibly accounting for changes in virulence and its ability to infect mosquitoes or hosts.
The Swiss cheese model for system failure
One way to understand how Zika spread is to use something called the Swiss cheese model. Imagine a stack of Swiss cheese slices. The holes in each slice are a weakness, and throughout the stack, these holes aren’t the same size or the same shape. Problems arise when the holes align.
With any disease outbreak, multiple factors are at play, and each may be necessary but not sufficient on its own to cause it. Applying this model to our mosquito-borne mystery makes it easier to see how many different factors, or layers, coincided to create the current Zika outbreak.
A hole through the layers
The first layer is a fertile environment for mosquitoes. That’s something my colleagues and I have studied in the Amazon rain forest. We found that deforestation followed by agriculture and regrowth of low-lying vegetation provided a much more suitable environment for the malaria mosquito carrier than pristine forest.
Increasing urbanization and poverty create a fertile environment for the mosquitoes that spread dengue by creating ample breeding sites. In addition, climate change may raise the temperature and/or humidity in areas that previously have been below the threshold required for the mosquitoes to thrive.
The second layer is the introduction of the mosquito vector. Aedes aegyptiand Aedes albopictus have expanded their geographic range in the past few decades. Urbanization, changing climate, air travel and transportation, and waxing and waning control efforts that are at the mercy of economic and political factors have led to these mosquitoes spreading to new areas and coming back in areas where they had previously been eradicated.
For instance, in Latin America, continental mosquito eradication campaigns in the 1950s and 1960s led by the Pan American Health Organization conducted to battle yellow fever dramatically shrunk the range of Aedes aegypti. Following this success, however, interest in maintaining these mosquito control programs waned, and between 1980 and the 2000s the mosquito had made a full comeback.
The third layer, susceptible hosts, is critical as well. For instance, chikungunya virus has a tendency to infect very large portions of a population when it first invades an area. But once it blows through a small island, the virus may vanish because there are very few susceptible hosts remaining.
Since Zika is new to the Americas, there is a large population of susceptible hosts who haven’t previously been exposed. In a large country, Brazil for instance, the virus can continue circulating without running out of susceptible hosts for a long time.
The fourth layer is the introduction of the virus. It can be very difficult to pinpoint exactly when a virus is introduced in a particular setting. However, studies have associated increasing air travel with the spread of certain viruses such as dengue.
When these multiple factors are in alignment, it creates the conditions needed for an outbreak to start.
Putting the layers together
My colleagues and I are studying the role of these “layers” as they relate to the outbreak of yet another mosquito-borne virus, Madariaga virus (formerly known as Central/South American eastern equine encephalitis virus), which has caused numerous cases of encephalitis in the Darien jungle region of Panama.
There, we are examining the association between deforestation, mosquito vector factors, and the susceptibility of migrants compared to indigenous people in the affected area.
In our highly interconnected world which is being subjected to massive ecological change, we can expect ongoing outbreaks of viruses originating in far-flung regions with names we can barely pronounce – yet.