United States health officials are warning against the spread of the West Nile virus (WNV) infection as more and more cases are reported across the country.

The Department of Health and Human Services in Iowa announced on Friday that the first case of WNV was reported this year in an older adult from Plymouth County. Officials confirmed that case through a test at the State Hygienic Lab.

Spread of West Nile Virus

In a statement, the department said that warm summer weather means that residents from Iowa are spending more of their time outside, which increases the risk of getting bitten by mosquitoes. Bites from infected mosquitoes are the main way humans contract the West Nile virus.

On the other hand, Nebraska's Department of Health and Human Services said in the first week of June that its first human case was found in the Three Rivers Public Health District. According to the New York Post, officials noted that the individual in question had not yet been hospitalized.

The United States Centers for Disease Control and Prevention (CDC) released data showing 13 cases of WNV since the beginning of this year as of June 13. More than a dozen cases were reported in Arizona, Georgia, Illinois, Louisiana, Nebraska, Oregon, Pennsylvania, South Carolina, and Wyoming.

Furthermore, the health agency showed more than 1,125 human cases of the West Nile virus last year. The Harris County, Public Health Mosquito Vector Control Division, was the one that confirmed a positive test for a mosquito sample in the Texas county.

Officials collected the sample from a mosquito trapped at a southwest 77005 ZIP code site. The division, in response, would activate evening spray operations where the sample was discovered and surrounding areas starting on Friday evening.

The virus entered the United States in 1999 and has since returned seasonally to spread the infection. The CDC noted that the West Nile virus had been the leading cause of mosquito-borne disease in the nation, according to Fox News.

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Primarily Bird-Based Infection

The division vice chief of internal medicine at UC Davis Health Medical Center in Sacramento, California, Dr. Christian Sandrock, said that one of the biggest misconceptions about the West Nile virus is that humans are natural hosts or that they can propagate the disease.

The medical professional said that the virus inadvertently infects humans and horses, which is largely a disease of birds. While rare, there may have been a few cases when the virus was transmitted through an organ transplant, blood transfusion, or from a mother to her child during pregnancy, childbirth, or breastfeeding.

Officials noted that roughly one in five people infected with the WNV develop symptoms, including headache, body aches, joint pains, vomiting, diarrhea, or rash. But almost 80% of the infected do not show any signs of being sick.

The WNV can, in some rare cases, result in inflammation of the brain and spinal cord, leading to severe symptoms such as paralysis, tremors, disorientation, and even death, said the Des Moines Register.

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