California serogroup (CSG) viruses include many viruses, such as the Jamestown Canyon and Snowshoe hare viruses, which are the most common in Québec. These viruses are also found throughout Canada and the United States. They are spread through the bite of an infected mosquito.
Transmission
CSVs are transmitted to humans by the bite of an infected mosquito.
Mosquitoes generally become carriers of Snowshoe hare virus by biting infected small mammals such as hares, squirrels, chipmunks and various rodents. For the Jamestown Canyon virus, they generally bite larger mammals such as deer and moose.
CSVs are not transmitted when a person comes into contact with an infected animal, nor when two people come into contact with each other.
In most cases, people infected with a CSG virus do not develop any symptoms.
However, some individuals may develop symptoms 2 to 14 days after the mosquito bite. The nature of the symptoms of CSG infection varies. The most frequent symptoms are:
Fever and chills
Headaches
Fatigue
Muscle or joint pain
Nausea, sometimes accompanied by vomiting, abdominal pain and diarrhea
In rare cases, CSG may cause a severe neurological infection, such as meningitis (infection of the lining of the brain), encephalitis (brain inflammation) or myelitis (spinal cord inflammation), which can be manifested by the following symptoms:
Numbness or muscle weakness
Hypersensitivity of the eyes to light
Visual disorders
Stiff neck
Agitation, disorientation or confusion
When to consult
You must consult a doctor promptly if you experience one of the symptoms associated with a severe form of CSG infection listed above.
Complications and sequelae
Following infection leading to neurological damage, sometimes permanent neurological impairment has been reported.
In rare cases, CSV can cause death.
Treatment
There is no specific treatment or vaccine against CSG viruses. However, most people who are infected recover without treatment.
People who are seriously ill may have to be hospitalized. They will then be treated to stabilize and improve their condition.
People at risk
Anyone can be infected by CSV.
The risk of infection is especially high when working in woodlands and forests.
Characteristics
In Québec, all forms of CSV infection have been reportable since 2019.