Two people in Michigan test positive for rare mosquito-borne ‘Jamestown Canyon virus’ that has a 50% hospitalization rate
Two people in Michigan have been diagnosed with a rare mosquito-borne virus – amid concerns that diseases passed on by insects are becoming more common.
The patients, from Detroit, tested positive for Jamestown Canyon virus – the first cases of the infection in the US this year.
They are said to be in stable condition. But in severe cases the disease can lead to encephalitis — or swelling of the brain — and seizures. Early warning signs include a fever, headache and muscle pain.
There is mounting concern that infections will rise as a longer warm season lengthens the period in which mosquitoes are active. It comes amid the US’ first domestic malaria outbreak in decades.
Two people in the Detroit metropolitan area have tested positive for Jamestown Canyon virus, the state’s Department of Health says
The virus is picked up by mosquitoes after they bite deer. It can then be transferred to humans when they are also bitten
The Michigan Department of Health said the patients lived in Oakland and Macomb, in the north of the Detroit metropolitan area.
Health officials are urging people in Michigan to take precautions against mosquito bites as a result.
Dr Natasha Bagdasarian, the chief medical executive at the state’s Department of Health, said: ‘It only takes one bite from an infected mosquito to cause a severe illness.
‘We advise using insect repellent and wearing long-sleeved shirts and long pants when outdoors during times when mosquitoes are active.’
She added: ‘It’s a good idea to take extra precautions during peak mosquito-biting hours, which are from dusk to dawn.’
About 17 cases of the disease are diagnosed in the US every year, with infections most likely in August and September, particularly in midwestern states.
Several state health departments say the infection is ‘rare’.
In Michigan, some 13 cases have been reported since 2011. The virus is most commonly detected in Wisconsin (132 cases in a decade) and Minnesota (74 cases).
Jamestown Canyon virus is picked up by mosquitoes when they bite infected mammals such as deer and Elk.
The disease can then be transmitted to humans when they are bitten, and travel around the body via blood vessels triggering illness.
Symptoms of the disease take about two days to two weeks to appear and can include fatigue, headaches, muscle aches and joint pains.
Around half of patients are hospitalized and a small number die. No American is known to have died from the infection, however.
In severe cases, the virus can start to attack membranes surrounding the brain and spinal cord causing encephalitis and meningitis leading to neurological problems.
Doctors use a blood test to diagnose the disease but have no targeted medicines, instead relying on IV drips and painkillers to treat infections.
The above map shows the number of cases reported by states from 2011 to 2022. Midwestern states had the most infections, although the virus remains rare
Medics have noted a rise in the number of Jamestown Canyon virus cases diagnosed in recent years.
There were about two to three a year between 2011 and 2012, data shows, but in 2021 this rose to as many as 32 per year.
People who were most likely to get infected included men who spent most of their time outdoors, where they were more likely to face a mosquito bite.
The virus was named after the place of its discovery, after being identified for the first time in Jamestown, Colorado, in 1961.