Health researchers are looking closely at how environmental factors intersect with human disease and illness.

In a Wednesday APHA Annual Meeting session on nature and human health, three researchers talked about their preliminary work exploring algae blooms in America, deforestation in Southeast Asia and pesticides in Latin America.

Kurrdeige Alexander, an MPH student at the University of Miami Miller School of Medicine, discussed her preliminary research on the health dangers of red tide, one type of harmful algae bloom common in Florida’s coastal waters.

Algae is often found in surface water and is generally not harmful. But when fed by pollutants, the plant organisms grow and can transform into a thick toxic bloom hazardous to humans and animals.

The toxins can cause flu-like symptoms in humans, including vomiting, diarrhea and sore throat, as well as liver damage and skin irritation, according to the Centers for Disease Control and Prevention.

Scientists studying Lake Erie’s algae blooms generally say the toxins are caused by agriculture runoff and higher water temperature due to climate change. But in the coastal waters of Sarasota County, Florida, causes are still up for debate, Alexander said. Agriculture, warming water and factory pollution are suspected, she told session attendees.

“We should get serious, face the truth and figure out what is causing this,” Alexander said.

In many parts of the tropical world, deforestation is accelerating. And so is malaria. Sonia Dattaray, a research assistant at EcoHealth Alliance, is involved in an ongoing study that examines whether deforestation results in more humans contracting the dreaded mosquito-borne disease.

Working in Malaysia in Southeast Asia, researchers found a correlation between areas of deforestation and an increase in malaria cases. The work suggests that health workers need to be aware of the possibility that malaria risk can increase among populations living in recently deforested areas.

“Forest loss and forest fragmentation are significantly associated with malaria incidence,” Dattaray said.

First discovered in Uganda in 1947, mosquito-borne Zika spread to the Americas, Southeast Asia and the Pacific Islands by 2016.

And according to Michael Welton, a postdoc candidate at the University of Georgia, Zika could be in Philadelphia and other highly populated parts of the U.S. by 2050. In adults, the Zika virus causes only flu-like symptoms, but pregnant women can experience miscarriages, premature births and birth defects. One birth defect is congenital Zika syndrome — a cessation to brain development and collapse of the skull.

Welton is studying if pesticide exposure contributes to Zika infection.

“Environmental exposures may interact with pathogens through altering the immune function, increasing pathogen violence and increasing risk of disease,” Welton told session attendees.

He and colleagues are testing for certain pesticides in urine samples from 1,500 pregnant women in Latin America where Zika is prevalent. Welton hopes the analysis will increase understanding of any cause-and-effect relationship between pesticides and developmental defects in children.

“It is also a unique opportunity to understand the potential interaction between Zika infection and pesticide exposure during pregnancy,” Welton said.

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