Zika Virus and Climate Disruption

BY ON January 25, 2016

Pregnant woman

Researchers have long been warning that climate disruption will help spread mosquito-borne diseases by fostering more mosquito-friendly habitats.

As a rare birth defect sweeps north from Brazil, health officials are raising the alarm about zika virus, linked to severe brain damage. Could climate change be fueling this epidemic?

Climate scientists have confirmed that 2015 was the hottest year on record by far, and that human-caused climate change is to blame. But it is less clear exactly how climate disruption interacts with the complex life cycle of mosquito-spread diseases, and whether the warming we have already set in motion may have fostered the spread of this virus, new to the Western Hemisphere.

Why are health officials worried?

Pregnant women infected with the otherwise mild zika virus may be at greater risk of giving birth to babies with microcephaly, a kind of brain damage. Reported cases of microcephaly in Brazil have recently soared from the norm of about 150 per year to 3,500 cases — just since October. One zika-related case has been reported so far in the US, in the child of a woman who had lived in Brazil during part of her pregnancy.

Health officials are concerned. Earlier this month, the Centers for Disease Control and Prevention (CDC) issued a travel warning for 22 countries, advising pregnant women and women planning to get pregnant to avoid travel to these places. The Jamaican minister of health advised women there to avoid pregnancy for the next six months to a year (!) while the zika epidemic spreads and we learn more about its health impacts. (There have been no known cases of zika in Jamaica.) More recently, CDC issued guidance for health professionals caring for pregnant women in the US, recommending screening for expectant moms who have traveled to zika-infected countries and have had some of the mild symptoms characterizing infection with the virus.

Most people who get zika don’t even have symptoms, so it’s impossible to screen for all the potential zika pregnancies. Health officials admit that widespread screening would overwhelm the US healthcare system – especially because there are few laboratories that currently can test for the disease. And the very usefulness of screening is in doubt, given that there is no treatment or cure for either zika virus or for microcephaly, and there is no vaccine for the virus on the horizon. Microcephaly can’t even be detected until well into the second trimester of pregnancy, so the screening seems designed to prepare pregnant women for the possibility that their baby may be born with severe brain damage.

This is a very disturbing development for pregnant women, especially those who have traveled to an impacted country, and for women thinking about getting pregnant. Because the virus is new to this hemisphere, most people have no immunity to it, and it is thought to be spreading quickly. The photos of babies with microcephaly are arresting. The brain damage is often fatal. The virus is likely to spread to the southern United States, according to the CDC.

Climate change and insect-borne disease

Dengue fever is one example of an insect-borne disease that thrives in warm environments. As the southern U.S. warms and flooding in those areas increases, dengue is likely to spread north into states previously unfamiliar with outbreaks of tropical diseases. Dengue has already been found in Texas, Florida, and Hawaii.

Zika is a mosquito borne virus similar to Dengue but with milder symptoms. It was named for a forest in Uganda, where it was discovered in the 1940s. Infected people can have symptoms similar to a cold, but most people infected do not have symptoms.

According to Dr. Jonathan Patz, director of the Global Health Institute at the University of Wisconsin, Madison, zika virus “may have a similar response” as dengue fever to temperature fluctuations. Dr. Patz studies the relationship between human health and climate change, and has been monitoring several infections, like tick-borne erlichiosis, for climate-related shifts in range. But zika virus was not on the health scientist’s radar. “This was a big surprise for me.”

The National Climate Assessment describes the connection between insect-borne diseases and climate change as very complex.

The geographic and seasonal distribution of vector populations, and the diseases they can carry, depend not only on climate but also on land use, socioeconomic and cultural factors, pest control, access to health care, and human responses to disease risk, among other factors….

Whether climate change in the U.S. will increase the chances of domestically acquiring diseases such as dengue fever is uncertain, due to vector-control efforts and lifestyle factors, such as time spent indoors, that reduce human-insect contact.

According to Patz, it is too soon to tell whether this outbreak relates to climate disruption. More research is warranted. But, he described the rapid spread of the virus, and the link to microcephaly, as “very concerning.”

As moms, we agree.



TOPICS: Children's Health, Climate Change, Pregnancy