Overview

The La Crosse virus is a type of arbovirus that is spread to people through the bites of infected mosquitoes. Most people infected with this virus do not develop any serious symptoms. However, children under 16 years old are especially at risk of developing more severe symptoms and long-term side effects from this virus - in fact around 75% of all cases of La Crosse virus infection are in children.¹ Understanding the symptoms of this viral illness is crucial for timely diagnosis and appropriate treatment to try to prevent more serious complications. 

Transmission of La Crosse virus to children

La Crosse virus transmission occurs predominantly through the bite of infected mosquitoes, which serve as vectors for the virus. The Aedes triseriatus mosquito is a known vector for La Crosse virus; it is a type of mosquito (also called the eastern tree hole mosquito) which is commonly found in wooded areas and near bodies of water throughout the United States.² Children who spend lots of time outdoors in these environments, particularly during the warmer months when mosquito activity is highest, are therefore at increased risk of exposure to the virus.

However, the La Crosse virus can survive over winter through the eggs of A. triseriatus mosquitoes which diapause during winter (a process which allows the eggs to delay their development until warmer months). These mosquitoes lay their eggs in stagnant water, such as that found in tree holes. Therefore, it is advised to regularly remove any sources of standing water from around your home to protect your children.³

Symptoms of La Crosse virus in children

Many children infected with the La Crosse virus do not show any symptoms of the infection. Those that do develop symptoms will typically show symptoms 5-15 days after the mosquito bite.¹ The onset of symptoms is often gradual, starting with non-specific flu-like symptoms that may include:

• Fever (usually lasting 2-3 days)
• Headache
• Nausea and vomiting
• Fatigue (tiredness)
• Lethargy (reduced activity or alertness)
• Muscle aches

In more severe cases, La Crosse virus can cause severe disease, such as encephalitis (inflammation of the brain) and meningitis (inflammation of the meninges - the protective membranes covering your brain and spinal cord), which can potentially be fatal. In these cases, you might see more serious symptoms, including:⁴

• High fever
• Neck stiffness
• Confusion or disorientation
• Seizures
• Coma
• Muscle weakness and tremors
• Numbness and paralysis
• Vision loss
• Death in very rare cases (<1%)¹

It is important to speak to your healthcare provider as soon as possible if you think that your children might have been infected with La Crosse virus. 

Diagnosis of La Crosse virus in children

To diagnose La Crosse virus infection, your healthcare provider will conduct a thorough physical examination and review your child’s medical history, making a diagnosis based on:⁵

• Signs and symptoms
• History of living or travelling in an area where La Crosse virus is known to circulate
• History of possible exposure to mosquitoes that could be infected with La Crosse virus
• Laboratory tests of blood or cerebrospinal fluid (CSF) samples to look for markers of the disease^6,7

Additionally, brain imaging studies may also be used to evaluate the extent of neurological complications, for example, looking for signs of encephalitis. This might include:⁷

• Magnetic resonance imaging (MRI)
• Computed tomography (CT) scan

Treatment and management of La Crosse virus in children

There are currently no approved antiviral treatments specifically for La Crosse virus infection. Instead, management primarily focuses on supportive care to alleviate the symptoms of infection and prevent any serious complications.⁸ Children with mild symptoms of La Crosse virus infection may be treated at home with rest, hydration, and over-the-counter medications to reduce fever and provide pain relief (such as paracetamol and ibuprofen).

In more severe cases, hospitalisation may be necessary for close monitoring of your child in case they start to develop elevated intracranial pressure (a build-up of pressure around the brain), seizures, or breathing problems. Treatment in hospital might include:^5,9

• Intravenous (IV) fluids to maintain hydration
• A nasal cannula, oxygen mask, or ventilator to provide respiratory support
• Anticonvulsant medication to manage seizures
• Medicines to reduce swelling in the brain

Prognosis and recovery of La Crosse virus in children

The prognosis for children infected with La Crosse virus varies depending on the severity of symptoms and any potential complications. In most cases, children experience a full recovery with supportive care and appropriate medical management. Children typically begin to feel better within a few days to a few weeks after symptom onset.

However, in cases with neurological involvement, complications can arise (such as encephalitis or meningitis) and recovery may be prolonged, requiring weeks to months of rehabilitation and supportive care. In these more severe cases, some children (around 6-15% of all diagnosed cases) might experience long-term effects or “neurological sequelae” which could affect the overall quality of life of your child. This might include:^4,10

• Neurological complications (e.g. seizures, paralysis, hearing loss, headaches)
• Cognitive delays and cognitive impairments (e.g. short-term memory loss, language difficulties, executive function difficulties)
• Behavioural and personality changes (e.g. anxiety, depression, impulsivity)
• Physical complications (e.g. fatigue, chronic pain, sleep disturbances, hemiparesis)

It is important to maintain long-term follow-up appointments with your healthcare provider to monitor for any persistent or evolving symptoms after your child has been infected with La Crosse virus.

Prevention of La Crosse virus infection in children

Unfortunately, there is currently no vaccine for the La Crosse virus. However, ongoing research aims to develop preventative vaccines that could reduce the spread of infection in endemic areas.

Instead, preventing La Crosse virus infection in children focuses mainly on minimising exposure to mosquito bites to prevent transmission of the virus to the children. This can be achieved through various preventative measures:

• Encourage your children to wear loose-fitting, long-sleeved shirts, long trousers, and socks when outdoors - particularly at dawn and dusk when mosquito activity is highest
• Use insect repellent containing DEET, picaridin, or oil of lemon eucalyptus to repel mosquitoes

IMPORTANT: Do not use products containing oil of lemon eucalyptus or para-menthane-diol (PMD) on children under the age of 3. 

• Cover strollers and baby carriers with mosquito netting
• Install screens on windows and doors to prevent mosquitoes from entering indoor spaces
• Remove and clean out sources of stagnant water around your home regularly (e.g. children’s paddling pools, tyre swings, tree holes) as mosquitoes lay their eggs in or near water

Most importantly, children and parents should be educated about the risks of mosquito-borne illnesses like La Crosse virus so that they can take the necessary preventative measures to reduce transmission rates.

FAQs

Where is the La Crosse virus found? 

Most cases of La Crosse virus infection occur in the United States, primarily in the Midwestern, mid-Atlantic, and southeastern states.

Is La Crosse virus contagious?

It is not thought that La Crosse virus is contagious. La Crosse virus cannot be spread by human-human contact (e.g. through coughing, sneezing, or touching another infected person). Instead, La Crosse virus is spread by the bite of an infected mosquito as a ‘vector’ of the virus.

Is La Crosse virus treatable? 

There is currently no specific treatment for La Crosse virus disease - antibiotics are not effective against viruses and no specific antiviral medication has yet been developed for La Crosse virus. Instead, supportive medication such as painkillers should be enough to treat mild cases of La Crosse virus infection. In severe cases, supportive therapy in hospitals might include respiratory support, IV fluids to maintain hydration, and medication to prevent other infections.

Summary

La Crosse virus infection in children presents with a spectrum of symptoms ranging from mild flu-like manifestations to severe neurological complications, including encephalitis. Although the majority of children recover from La Crosse virus infection within a few weeks, some might experience life-changing long-term effects after a serious infection. Early recognition of symptoms, prompt diagnosis, and appropriate management are essential for ensuring favourable outcomes. By implementing preventive measures to reduce the risk of exposure to mosquitoes carrying this virus and promoting community awareness, the risk of serious La Crosse virus infection among children can be reduced. Continued research efforts aimed at vaccine development and vector control strategies are critical for preventing future outbreaks of this potentially debilitating disease.