10 people have died from the West Nile Virus in Arizona since beginning of September
As of Sept. 27, the West Nile Virus has killed 10 people this month according to a report by the Arizona Department of Health Services.
The majority of the deaths occurred in Maricopa County, with the first person dying at the beginning of September, according to ADHS public information officer Tom Herrmann.
Up until August 1, there were zero to three new cases reported each week in Arizona, according to ADHS data. Confirmed cases doubled from two to four in the first week of August, peaking at 24 to 25 per week in late August and early September.
Herrmann said there can be a delay in cases showing up in ADHS's data because of the time required for them to be reported and investigated. Someone who gets sick might take a week before testing and results take another two to three days before getting reported. Then it may take ADHS anywhere from a few to days to as long as two weeks before the case is counted because medical records are reviewed and tests confirmed if necessary.
Maricopa, Pinal counties reporting high West Nile virus activity
The three largest counties in Arizona have the most cases so far. Maricopa County had 98 confirmed and 46 probable as of Monday. Pinal County had 9 confirmed and 14 probable. Pima County had 3 confirmed and 1 probable.
"West Nile virus was first seen in Maricopa County in 2003, and in that time, we’ve never seen more mosquitoes infected with the virus than we are seeing this year," Maricopa County said in an email newsletter on Sept. 20.
Even though Pinal County is about half the size of Pima, more cases have been reported.
"Here in Pinal County, Public Health has 22 cases under surveillance. This is much higher than normal as the average number of cases since 2016 has been 5 cases per season," the county said in an email newsletter on Sept. 23.
There are a number of factors that could contribute to the difference in county numbers.
"Counties might have residents who seek different amounts of healthcare, or providers who test and report cases more or less than in other counties. It is possible that in Pima County there might be more cases than what has been reported," Herrmann wrote in an email to The Arizona Republic.
Older adults more likely to get sick with West Nile virus
On the other hand, counties with more cases might have more West Nile virus-positive mosquitoes or older residents who are more at risk of acquiring the disease.
People older than 60 and with certain medical conditions such as cancer, diabetes, hypertension or kidney disease are at a higher risk of severe illness, Herrmann said.
It also seems males acquire the virus more often than females, but ADHS does not know why they have a higher rate of infection.
About one in five people will show symptoms. The most common symptoms are flu-like, including fever, headache, body ache and muscle weakness.
Severe illness affects the central nervous system. Symptoms include stiffness of the neck, inflammation of the brain and/or meningitis.
Herrmann said cases could increase again this year.
"West Nile Virus season can last until the end of October in Arizona," he said.
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