New Study Shows West Nile Virus Migrates Out of Arizona

The History of West Nile Virus

The West Nile Virus (WNV) was named for the location where it was originally found- the West Nile district in Uganda. It was discovered in Africa in 1937 and in 1999 the first case was documented in the United States. It’s predicted that its geographic spread was a result of migrating birds. The disease is contracted by a simple mosquito bite.

Fortunately, while the virus is still active in the United States, most people who contract it do not feel any symptoms. The U.S. Centers for Disease Control and Prevention estimates that 1 in every 5 people who have WNV develop symptoms. These include headache, nausea, and fever. That said, serious cases of the illness can be fatal. This is normally a result of the disease spreading into the brain. However, this severe form of WNV only affects one in every 150 people with the diagnosis.

Currently, West Nile Virus causes 96% of mosquito-borne disease diagnoses in the U.S. This makes it the leading mosquito-born illness in the country. It is present in every state except for Hawaii and since 1999 has caused 1,000 deaths.

While there are no ways to prevent WNV in terms of vaccines, and there are no treatments for the condition, the simple use of mosquito repellent can help reduce risk. Even wearing clothing that has more coverage can help deter bites.

The West Nile Virus in Arizona

In most states in the United States, the WNV is only active and mobile during the summer and the fall. It can’t survive well in cold temperatures and dissipates completely when in freezing temperatures. But in Arizona’s Maricopa County, freezing temperatures are an extremely rare occurrence.

A new study conducted by Northern Arizona University as well as the Translational Genomics Research Institute has shown that the West Nile Virus may be a permanent part of Arizona’s ecosystem due to its moderate temperatures.

This study was co-authored by the Maricopa County Environmental Services Department.

The Study

The Maricopa County Environmental Services Department Vector Control Division worked to trap mosquitoes at 787 different sites in the Phoenix area. The genetic material collected from the WNV samples in these mosquitoes was then analyzed and researchers were able to create a genomic family tree of the virus.

With this data, a computer algorithm was used to create a model which outlined the movement of the virus from one state to the next. It was through this model, that researchers came to believe that the WNV is a permanent resident of Arizona.

Additionally, these researchers were able to distinguish between two dominant strains of the virus. The first was NA/WN02, which they found has been in Maricopa County for around four years. The second, SW/WN03, is projected to have been in residence for around seven years. The same protocol which identified these individual strains of the virus have been used in studies of the Zika virus as well. It’s called whole genome tiled amplicon sequencing.

The Benefits

Something positive stemming from this study is that the new information will allow public health officials to track the West Nile Virus more accurately as it moves. In addition to tracking the two strains of the virus studied in this simulation, they will also be able to detect new strains of the virus. This means they can facilitate targeted vector control in addition to education campaigns for the public.

Currently, researchers are using the findings from this study to investigate how the virus spreads from Arizona to other states, specifically in the west.

You can read more about this study and what these findings mean for future West Nile Virus research here.


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