Overview

Jamestown Canyon virus (JCV) is a rare virus spread by infected mosquitoes. This virus is found across the United States, particularly in the northern states¹. The name ‘Jamestown Canyon virus’ comes from the place where the virus was first isolated from mosquitoes in 1961; Jamestown, Colorado². This article will explain the causes, symptoms, diagnosis and treatments of JCV and improve your understanding of the virus. 

Causes of Jamestown Canyon Virus

JCV is an arboviral disease, which is an infection caused by the bite of infected arthropods (insects). Other arboviral diseases include Eastern equine encephalitis, West Nile virus and Yellow Fever^з.  JCV specifically is spread by mosquitoes infected with the virus; most cases occur in the late spring or mid-autumn, based on increased mosquito populations¹. The mosquitoes become infected after they have fed off other animals that carry the virus in their blood. These other animals are called amplifying hosts. Amplifying hosts for JCV tend to be white-tailed deer, but moose, elk and bison may also play this role⁴. 

JCV cannot be spread from human to human through coughing, sneezing or touching someone who is infected with the virus⁵. However,  arboviral infections can be spread by blood transfusion, organ transplantation, sexual contact, or from pregnant mother to child; JCV has only been suggested to be at risk of transmission through blood transfusion and organ transplantation, and even this has not been confirmed. However, it is important to bear in mind if you are experiencing symptoms of the virus⁶.

Signs and symptoms of Jamestown Canyon virus

Many people with JCV do not have symptoms, which is known as being asymptomatic. However, the exact number of asymptomatic cases compared to symptomatic cases is unknown. For those that do end up having symptoms, the time from when they are bitten by a mosquito to the time they begin to feel ill (known as the incubation period of the virus) can be anywhere from a few days to two weeks².

Initial symptoms can include a fever, headache, and fatigue. Some patients present with a cough, sore throat, runny nose, or the mucous membranes of the nose or oropharynx becoming inflamed (known as pharyngitis or rhinitis respectively)².

JCV can cause severe disease; for example, in 54-79% of reported cases, patients experienced neuro-invasive symptoms such as encephalitis (an infection of the brain), meningitis) or both (meningoencephalitis)⁷. Symptoms for these more serious infections include a stiff neck, seizures, confusion, difficulty speaking and/or loss of coordination⁵. 

Deaths from JCV are rare - of a study of 31 JCV cases, no deaths occurred ¹ - but about half of all infected patients are hospitalised². 

Management and treatment for JCV

Unfortunately,  there are no specific medicines or vaccines to treat JCV⁷. Treatments therefore focus on managing and relieving the symptoms of this virus, through rest, ingesting lots of fluids to stay hydrated, and pain medications to help with discomfort. If a patient needs to be hospitalised, this can provide supportive treatment such as fluids through an intravenous (IV) drip, nursing care and pain medication that is unavailable over-the-counter⁵.  Intensive care is needed for those with seizures, cerebral oedema or decreased consciousness². 

Diagnosis

When diagnosing a patient with JCV, a doctor will take several factors into account. For example, whether the patient has lived or travelled in an area where the virus is known to exist, and what symptoms a patient is experiencing. A patient’s blood or cerebrospinal fluid (CSF) can be tested to see if they have JCV; the presence of a substance known as anti-JCV immunoglobulin M is usually evidence to give a JCV diagnosis, however this may also indicate several other viruses in the California serogroup that are closely related to JCV such as La Crosse virus, snowshoe hare virus or California encephalitis virus^1,². Symptoms may also be similar to these other viruses,  resulting in many cases of JCV going unidentified.  JCV is also underdiagnosed due to many cases being asymptomatic². 

Risk factors

As JCV is spread through the bite of infected mosquitoes, those who are more frequently exposed to mosquitoes are at a higher risk of contracting the virus. For example, working outdoors, living in affected areas where mosquito populations are high, or spending time near standing water are all risk factors. Immunocompromised people may be at a higher risk of hospitalisation from JCV and are more likely to suffer complications and more severe infection². 

FAQs

How can I prevent the Jamestown Canyon virus?

JCV can be prevented through reducing contact with mosquitoes. Using insect repellent, and covering arms and legs with long, loose-fitting clothing can also help, as well as treating clothes with permethrin-based products and using screens on windows and doors⁵.  Not allowing standing water to collect, for example by emptying children’s pools, pet bowls or clogged gutters weekly, will help prevent mosquitos from laying eggs². 

How common is the Jamestown Canyon virus?

JCV is considered to be rare in humans. Between 2004 and 2012, there was an average of 1.7 cases per year, however, with better diagnostic methods and awareness this increased to 29.2 cases per year between 2013 and 2018⁸. As mentioned before, many cases are asymptomatic and go undiagnosed, so its actual prevalence is likely higher than this. As the virus cannot be spread between humans through coughing or contact, this does not put others at risk²,⁵. 

What can I expect if I have a JCV?

You may be asymptomatic, it would be unlikely you would realise that you have the virus, or you may experience the symptoms detailed above. If you are experiencing symptoms of JCV, expect to spend time resting, stay hydrated and use pain medications if necessary. If you have more serious complications such as meningitis, hospitalisation is necessary,⁵. 

When should I see a doctor?

If you are experiencing discomfort that cannot be managed by over-the-counter pain medication, or suspect that you have severe complications such as meningitis, it is advised to seek medical assistance immediately.

Summary

JCV is a relatively rare virus spread by the bite of infected mosquitoes. Many people do not experience any symptoms, however, some suffer from fatigue, headaches and coughing, whilst others need to be hospitalised due to more serious complications such as meningitis or meningoencephalitis. There are no specific treatments for JCV, other than rest, pain medications and fluids, which help relieve the symptoms.