West Nile virus, Zika virus, Lyme disease, and dengue are all projected to become more common in the United States as temperatures continue to rise.
- The Trump administration released a major climate report on Friday that outlines current and predicted effects of climate change in the US.
- In the report, scientists project that the number of West Nile virus cases in the US will more than double by 2050 because of rising temperatures.
- Zika virus, Lyme disease, dengue, and other infectious diseases are expected to become much more common, too.
The number of West Nile virus cases in the United States is expected to more than double in the next 30 years.
That's one of the dire predictions in the climate report that the Trump administration released on Black Friday. Scientists project that as average temperatures continue to rise, the geographic ranges of disease-carrying insects like mosquitoes and ticks will grow, putting more Americans at risk of getting infected with West Nile virus, Zika virus, Lyme disease, and dengue in the coming decades.
The report, called the National Climate Assessment, is the fourth in an ongoing series mandated by a 1990 law. It analyzes the possible consequences of various levels of climate change in the US.
With respect to West Nile virus, the report says, the US could see about 3,300 more cases each year by 2100 if current greenhouse-gas emission patterns continue. (That's under a scenario in which we keep putting more heat-trapping gas into the atmosphere for the rest of the 21st century.)
The annual costs of those illnesses and deaths by 2050: $3.3 billion.
The report also looks at a more optimistic scenario, which shows greater reductions in greenhouse gas emissions over the next 30 years, with further decreases after that. In that case, roughly half of the additional West Nile cases, along with half the costs, could be avoided.
Valley fever and other diseases are projected to become more common as well
The report also predicts that some regions of the US will see more drought, while others could see a 20% increase in precipitation. Almost everywhere, average annual temperatures will rise. Combined, these factors will likely lead to higher rates of many other infectious diseases in addition to West Nile virus.
For example, droughts and dry conditions are known to cause a spike in cases of Valley fever. More cases of the illness, which is caused by a fungus in soil, have already been observed in states like Arizona and California. Valley fever sends people to the hospital in about 40% of cases and causes 75% of infected people to be unable to perform daily tasks for weeks or months.
The geographic ranges of pests that carry tropical and subtropical diseases could expand as well.
Outbreaks of dengue, for example, have recently been reported in southern Texas because the mosquitoes carrying the tropical disease no longer get killed off by low temperatures in the state.
Alaskans, meanwhile, could get infected with tick-borne illnesses like Lyme at higher rates. These diseases are rare there now, but residents have already started to find non-native ticks on dogs (that did not travel outside the state).
More Americans could also face a risk of waterborne diseases
Waterborne diseases may also become more common as temperatures rise, the report said.
A rise in instances of diarrhoeal disease, for example, has been linked to flooding, heavy rainfall, and high temperatures. These factors, and the sanitation issues they cause, could also increase rates of infections like cryptosporidiosis, which causes diarrhea, fever, and stomach pain.
In addition to nationwide trends in infectious disease transmission, the report looks at some specific locations that are at risk. In Alaska, for example, environmental changes could reduce residents' access to clean water, since tundra ponds that provide clean water are shrinking due to climate change. Riverbank erosion could also lower water quality, and wastewater treatment systems could get damaged from coastal erosion or storm surges.
This might force some Alaskans to use untreated water, reuse water, or ration water, which could cause waterborne infectious diseases to become more common, the report said.
Heat waves and high temperatures could also make Americans more vulnerable to germs in water, such as Vibrio bacteria, which can cause deadly infections. In the Northeast, shellfish are projected to make more people sick because warmer waters lead to to shell disease in lobsters and other pathogens in oysters.
The transmission risk for some diseases could go down because of very high temperatures, the report said, and economic development could also reduce people's risk of getting some diseases. But overall, it's an upward trend.
According to the report, the high-emissions, business-as-usual scenario would cause thousands of additional deaths in the US.
“In the absence of more significant global mitigation efforts, climate change is projected to impose substantial damages on the US economy, human health, and the environment,” the report said. “It is very likely that some physical and ecological impacts will be irreversible for thousands of years, while others will be permanent.”