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West Nile virus, other infectious diseases could spread by 2050



West Nile Virus California
vector control team leaves after spraying pesticide through a Del
Mar neighborhood where increasing numbers of mosquitoes have
tested positive for West Nile virus in San Diego, California,
U.S. May 18, 2016.


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

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

california drought
worker adjusts a water irrigation system in a field near San
Ysidro, California March 31, 2016.

Reuters/Mike Blake

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

Outbreaks of dengue, for example,
have recently been reported in southern
because the mosquitoes carrying the tropical disease no
longer get killed off by low temperatures in the state.


, 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

More Americans could also face a risk of waterborne

hurricane florence flooding Wilmington, North Carolina
from Sutton Lake has washed away part of US 421 in New Hanover
County just south of the Pender County line in Wilmington, North
Carolina on Sept. 21, 2018.

Born/The Star-News via AP

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

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

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