Ever since the dawn of humankind, climate has been inextricably tied to human health. A stable climate and receding Ice Age were essential to the rise of modern civilization. From the physiologic stress of excessive heat, to the widespread failure of agriculture, in many and varied ways, the climate crisis is first and foremost an advancing public health crisis.
A hotter, more humid world is already becoming a world of more serious, virulent infectious diseases. West Nile, Lyme disease, dengue fever, Chagas, yellow fever, chikungunya, Rocky Mountain spotted fever, Rift Valley fever, Japanese encephalitis and malaria are just a few of the many infectious diseases attacking more victims and spreading far beyond their previous geographic confines. Global temperatures aren’t the only things that broke records in 2015. For example, the number of victims of dengue fever in Brazil reached 1.58 million, an all-time high, up from 78,000 cases in 1990. The Centers for Disease Control and Prevention (CDC) recently concluded that the number of annual cases of Lyme disease in the United States was 300,000 – 10 times higher than their previous estimates – and that the disease is spreading north into Canada.
Heat, precipitation and humidity augment the life cycle, reproduction and even biting activity of mosquitoes and other insects that carry these diseases. Even the viruses, bacteria and parasites carried by the insects can have their survivability exponentially enhanced by warmer temperatures. The World Health Organization notes, “Extreme weather-related events have made disease transmission pathways worse.” Many insect-borne diseases, never before seen in the United States, have arrived at our doorstep.
One of these is a truly frightening new kid on the infectious disease block that has even managed to get a little attention from media outlets like The Wall Street Journal, Forbes, Business Insider, CNN, The New York Times, Scientific American and Science News. It’s called “Zika” – which is spread by mosquitos – and an outbreak erupted in 2015 in Brazil after an unusually hot and rainy, El Niño summer, and the worst flooding there in 50 years.
The mosquito species that transmits the Zika virus is found throughout the world, and is common in Florida and along the Mexican border, although so far, the pathogen itself has not been found there. Only about one in five people infected with Zika will develop symptoms, and the most common symptoms are rather mild fever, rash, joint pain and conjunctivitis typically lasting about a week. Zika could also rarely result in Guillain-Barré syndrome in adults, a well-known disease in which muscle weakness may evolve into subacute or chronic paralysis. All these other existing insect-borne diseases are bad enough; why all the new fuss about Zika?
Evidence is rapidly accumulating that if a pregnant mother contracts Zika, her baby can develop a devastating deformity called microcephaly, a congenital condition associated with an unusually small skull and brain, the result of incomplete brain development. The first case of Zika in the Western Hemisphere was reported in Brazil in May 2015. Four months later, the number of cases of microcephaly in Brazil had increased 10 times. By the end of 2015, 3,174 babies with the defect had been born in Brazil, more than 20 times more than the year before. It appears to be just the beginning of a terrifying and explosive epidemic.
Most of the mothers involved reported Zika-like symptoms early in their pregnancies, and the virus seems to be capable of passing from the mother through the placenta to the fetus. Zika has been found in the amniotic fluid of mothers who gave birth to microcephalic babies. Brazil is in full-blown panic mode. The Rio Times reports, “Brazilian laboratories are working extra shifts to process all suspected Zika virus cases in newborn babies with microcephaly.” In November 2015, the country’s Health Ministry declared Zika to be a national emergency, even though its connection with microcephaly is not yet completely understood or conclusively proven.
The Brazilian government has deployed thousands of army troops and inspectors making house-to-house searches to obliterate any possible mosquito breeding grounds like stagnant pools of water. Unfortunately, part of their response has been to massively increase pesticide spraying in affected areas, which carries its own risk of fetal neurotoxicity, and dozens of studies have shown strong links between pesticides and neurodegenerative diseases, loss of IQ and behavioral disorders throughout the age spectrum. The gold standard in mosquito repellants, DEET, is also likely toxic to nervous systems, especially when the subject is also exposed to pesticides.
Brazilian officials have even gone so far as to advise women to avoid getting pregnant if at all possible. In less than eight months, Zika has gone from one confirmed case, to infecting between 500,000 and 1.5 million Brazilians. The Wall Street Journal reports that a former Brazilian health minister and executive director of the South American Institute of Government in Health expects there to be 15,000 babies born with microcephaly in Brazil in 2016.
Zika has already reached 14 Latin American and Caribbean countries. It has spread to Mexico and Puerto Rico, and the CDC is warning that it is likely to reach the United States. In fact, a few cases of Zika have already emerged among American travelers returning to the US from Latin America.
To be sure, microcephaly can also be caused by genetic abnormalities, exposure to toxins like mercury, maternal alcohol use and measles. But none of these predisposing factors can account for this new epidemic.
Climate change deniers are already in a scientific no man’s land, in defiance of every relevant scientific discipline – including physics, atmospheric chemistry and climate science – if not the scientific method itself. To brush off the rise in infectious diseases, they will be increasingly making claims in defiance of medical and biologic science as well.
At the top of the list of reasons to act with urgency on the climate are the public health consequences that will unfold if we don’t. You can add Zika and the epidemic of microcephaly to that long and growing list.
With every passing month, the stakes for humanity’s future are rising in lockstep with temperatures and sea levels. For years, the heartbreaking symbol of climate change has been the image of a polar bear stranded on a floating patch of ice. The new symbol of climate change’s effects may instead become the image of a human baby with microcephaly.