Zika virus (ZIKV) has affected roughly half a million people in the Western hemisphere in recent years, including US veterans. Older veterans and those with comorbidities are at an increased risk of hospitalizations and neurological complications after a ZIKV infection, researchers now report in PLOS Neglected Tropical Diseases.

ZIKV is a flavivirus transmitted primarily by Aedes mosquitos. An outbreak spanning 2015 to 2016 affected hundreds of thousands of people, including more than 5,000 cases in the continental U.S. and more than 36,000 in Puerto Rico and the Virgin Islands. The Veterans Health Administration (VHA) has health care facilities throughout the U.S. and territories and performs ongoing surveillance for emerging pathogens.

In the new work, Patricia Schirmer of the Department of Veterans Affairs, and colleagues performed a case series study of all ZIKV cases in VHA hospitals in 2015 and 2016. They analyzed the patient characteristics and clinical outcomes of 736 ZIKV positive patients out of the 1,538 patients who were tested for ZIKV during this time period.

736 (48%) of the patients tested positive for ZIKV; 655 (89%) were male and 683 (93%) were seen in the VA Caribbean Healthcare System. 94 (13%) of the patients were hospitalized and 19 (3%) died after their ZIKV infection. In general, veterans who were older and had other underlying health problems -- including congestive heart failure, dementia, and acute kidney injury -- were more likely to be hospitalized. If a patient presented with a rash, they were less likely to be hospitalized, but if they presented with initial neurological symptoms, they were more likely to be hospitalized.

"Better understanding of those patients most at risk for severe disease can help providers when evaluating and treating patients with ZIKV infection," the researchers say.