LA County saw longest recorded season of West Nile virus activity last year

From Whittier Daily News
February 1, 2018

A deadly mosquito-borne virus that typically spreads in the summer and fall months lingered in Los Angeles County until Christmas last year, infecting more than 260 people and killing 27, health officials said this week.

It was the longest recorded season of West Nile virus activity, spanning about 30 weeks in 2017, with the last date of symptom onset occurring Dec. 24, according to Sharon Balter, director of the Los Angeles County Department of Public Health’s Acute Communicable Disease Control Program.

Previously, the longest West Nile season the county had experienced since the virus was first detected in 2003 lasted about 23 weeks, Balter said.

“The season has been getting longer and longer,” she said.

Why? Balter suspects several culprits, including unseasonably warm temperatures in November and December. Other factors could include the particular travel paths of birds and mosquitoes as well as increase in the number of older adults who are more at-risk of illness.

“The ecology of West Nile virus is incredibly complex,” Balter said, adding that human behavior could also be a factor. “One theory is that due to the heat waves later in the year, people were staying out later, staying out more and staying out after dark.”

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