Multistate (USA) - Update: West Nile virus, >1,600 cases

October 10, 2018
CDC (US); State Health Agencies

As of October 2, 2018, a total of 48 states and the District of Columbia have reported West Nile virus infections in people, birds, or mosquitoes in 2018. Overall, 1,611 cases of West Nile virus disease in people have been reported to the Centers for Disease Control and Prevention (CDC). Of these, 933 (58%) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 678 (42%) were classified as non-neuroinvasive disease.

Nebraska reported the highest number of human cases at 195, followed by North Dakota (171) and South Dakota (141).

Below are the updates from some state health agencies.


Today the Mississippi State Department of Health (MSDH) reports two new human cases of West Nile virus (WNV), bringing the state’s total to 42 so far for 2018. The reported cases are in Hinds and Calhoun counties.

So far this year human cases have been reported in Adams (2), Attala, Calhoun (3), Copiah, Forrest (2), Harrison (4), Hinds (16), Itawamba, Jones, Lauderdale, Madison (2), Marion, Oktibbeha, Pearl River, Rankin (2), Walthall and Washington (2) counties. In 2017, Mississippi had 63 WNV cases and two deaths.

Peak WNV season in Mississippi typically ends in September, but activity is still being reported statewide, said MSDH State Epidemiologist Dr. Paul Byers. All Mississippians should take precautions against mosquitoes, regardless of reports of human cases in specific counties.

Byers said that while most people with WNV recover without any long-term problems, some develop a more severe infection that can lead to complications and even death, especially those over 50 years of age.

Symptoms of WNV infection are often mild and may include fever, headache, nausea, vomiting, a rash, muscle weakness or swollen lymph nodes. In a small number of cases, infection can result in encephalitis or meningitis, which can lead to paralysis, coma and possibly death.


The Los Angeles County Department of Public Health (Public Health) has confirmed the first death due to West Nile virus (WNV) for the 2018 season in Los Angeles County. The patient, a resident of the San Fernando Valley area, was hospitalized in early September and died from WNV- associated neuro-invasive disease. A total of 38 cases have been documented in Los Angeles County this year (excluding Long Beach and Pasadena as cases identified in those cities are reported by their local health departments).

“Our thoughts and prayers are with this person’s family and friends during this sad time. This should remind all of us that West Nile virus is a serious disease,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer. “Everyone should take precautions by using Environmental Protection Agency (EPA)-registered mosquito repellent when outside and checking weekly for items that collect standing water in their homes or yards where mosquitoes can breed. Items that can hold water, even as small as a bottle cap, should be cleaned, covered or cleared out to stop mosquito breeding.”

Public Health has documented persistently elevated numbers of WNV cases in LA county over the previous 5 years, at an average of 221 cases per year. Over three-quarters of reported cases have had severe disease and approximately 7% of patients with severe WNV have died from complications. In 2017, a record of 27 deaths were documented among LA County’s 268 cases. Reduction of mosquito breeding sources and protection from mosquito bites are key to prevention.

According to the California Department of Public Health (CDPH), there have been 118 human cases of WNV reported in 26 counties. Five WNV-related fatalities have been reported to CDPH this year from five local health jurisdictions: Butte (1), Glenn (1), Placer (1), Yolo (1), and Yuba (1) counties, as of October 5, 2018.

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