Health experts are sounding the alarm over the rise of a deadly insect-borne disease following America’s first death from the virus this year.

An unnamed individual in Maricopa County, Arizona, was diagnosed with West Nile Virus, which is becoming more prevalent in the US due to a warming climate. 

They were among the one percent of patients who develop a severe form of the virus, which causes dangerous swelling of the brain.

This occurs when the virus crosses the blood-brain barrier and infects the brain and/or spinal cord, leading to conditions like encephalitis, meningitis, or paralysis. 

Officials revealed the victim was an older adult with underlying health conditions.  

They were the 17th human case of the West Nile virus in the Maricopa County area and among the 51 human cases nationwide.

While West Nile virus typically causes mild symptoms, individuals with certain medical conditions – such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants – are at greater risk of serious health complications.

Currently West Nile virus activity appears to be at a relatively stable level, but the presence of the virus in places it typically doesn’t appear is raising concerns among experts. 

The West Nile virus is the most common mosquito-spread disease in the continental US

This is because higher temperatures shorten the time it takes for the virus to incubate within the mosquito and become infectious.

Additionally, warmer temperatures can enhance mosquito survival and reproduction rates, further amplifying the spread of the virus.

Maricopa County’s chief medical officer Dr Nick Staab said: ‘This tragic loss is a reminder that West Nile virus can be serious, especially for older adults and those with existing health conditions.

‘Monsoon season brings much-needed rain, but it also creates ideal conditions for mosquitoes to breed.’

The most cases have been recorded in Arizona (17 cases), followed by Louisiana (seven), Oklahoma and Texas (five) and Tennessee (three).

Other states with human cases of West Nile virus are California, Alabama, Georgia, Kansas, Mississippi, North Dakota, Nebraska, Ohio, South Carolina, and Virginia. 

So far this year, there have been 51 human cases of West Nile virus in the US, including 24 severe or ‘neuroinvasive’ cases.

Last year, there were 748 human cases of the virus recorded, including 515 neuroinvasive cases.

The worry among experts is that West Nile virus is spreading to new areas, and mosquitoes carrying the virus are being found in previously unaffected regions.

This is partly due to climate change, which is expanding the range of mosquito-borne diseases.

It is currently the leading cause of mosquito-borne disease in the US.

Recently, West Nile virus has been detected in mosquitoes in New York City, but no human cases have been reported.

Once a person is bitten by an infected mosquito, It generally takes between three and 14 days for the disease to develop.  

Around 80 percent of infected people are asymptomatic (no symptoms), but 20 percent will develop fever, headache, and body aches.

In rare cases – about 1 in 150 – the virus can cause severe complications as it spreads to the brain – like encephalitis or meningitis – which may lead to paralysis, long-term disability, or death. 

People over the age of 60 are at greater risk for severe illness if they are infected, as are those with with certain medical conditions, such as cancer, diabetes, hypertension, and kidney disease. 

There is no specific treatment for the virus or vaccine, but 80 percent of cases are mild, where sufferers may experience flu-like symptoms or rashes. 

In more severe cases, patients have reported paralysis and memory loss. 

Prospero Rangel, 78, beat cancer but was left relearning how to walk after contracting West Nile virus last year. 

So far, there have been 51 reported human cases of West Nile virus so far this year across the US. Arizona has the most number of cases at 17

Prospero Rangel, pictured with his daughter Sara Salzer, was outside his home in Brazos County when he sustained two bites from a mosquito. He went on to contract West Nile virus

He was outside his home in Brazos County, Texas, when he was bitten and immediately began feeling ‘so itchy’. 

Over the following days he began suffering body aches, joint pain, weakness and a fever before being admitted to hospital a week later.

Rangel’s daughter, Sara Salzer, said following his diagnosis: ‘We’ve been told that there are going to be some symptoms that are going to stay with him for a while. 

‘We were even told that he may have to do outpatient therapy for the next year.’

The CDC states that the best way to prevent West Nile is to protect yourself from mosquito bites.

Bite prevention tips include using insect repellent, wearing long-sleeved shirts and pants, and using mosquito repellent devices outside and around the home. 

Following the first human death, residents in Maricopa County are being encouraged to remove standing water while ensuring that lawn irrigation and onsite sewage systems are properly maintained. 

Larvicide can also be used to treat any areas where mosquitoes could lay eggs.