Powassan (POW) Virus Ticks, Symptoms, Spread, Treatment, Prevention

There are several infections that may be caused by tick bites. The infectious agents, bacteria or viruses, are carried by a tick and enter the bloodstream when the tick feeds on a person. Most of the time these infections are mild and do not lead to any serious complications. However, there are cases where tickborne diseases can be serious and even fatal for some people.

Some of the more well known tickborne diseases are Lyme disease and Rocky Mountain spotted fever. However, a new disease that can be caused by a tick bite is now emerging as a potential public health problem. This has arisen since the virus can now be spread by a tick that commonly bites humans whereas in the past it was only spread by ticks that rarely fed on humans. It is known as the Powassan virus.

What is Powassan virus?

Powassan (POW) virus is an arbovirus that can infect humans. The virus is spread by tick bites and cannot be transmitted from human to human. Usually the illness caused by Powassan virus is mild but in some cases it can be severe and even life-threatening. Overall Powassan virus infections are uncommon, however, a recent change in the type of tick that carries the disease has raised concerns about its more rapid spread.

Infections caused by Powassan virus have been identified in the United States, Canada and Russia. In the United States, these infections are more likely to be contracted in the Northeast and Great Lakes regions because the type of tick that carries the virus is more likely to be found in these areas. There have been approximately 75 cases in the United States in the past 10 years but it may become more prevalent in coming months and years.

How is Powassan virus spread?

As mentioned, the Powassan virus is spread by tick bites. The virus can enter the bloodstream within minutes of attaching and feeding on a person. It is specifically carried by the Ixodes species and specifically Ixodes cookei, Ixodes marxi and Ixodes scapularis, may carry the infection from animals to humans.

However, Ixodes cookei and Ixodes marxi rarely bite humans unlike Ixodes scapularis ticks which frequently bites humans. The latter is also known as the deer tick and is also responsible for transmitting Lyme disease. Unlike with Lyme disease, the tick does not have to be attached and feeding for hours to spread the POW virus.

Even if a human is infected, a feeding tick cannot acquire the virus to then transmit it to another human it may feed on later. The reason for this is that the virus does not reach a large enough concentration in the bloodstream of humans to be a source for other human infections. Therefore humans are referred to as “dead end hosts”.

Read more on tick diseases.

Signs and Symptoms

Firstly, most people who do become infected with the Powassan virus will not develop any symptoms. Secondly, when a person does develop symptoms it is usually mild. However, there are instances where Powassan virus infection progresses to a severe illness involving the brain (encephalitis) and its surrounding membranes (meningitis). This can be fatal.

The signs and symptoms of Powassan virus infection can develop anywhere between 1 week to 1 month after contracting the infection through a tick bite. Since many people may either not recall the tick bite or not even have noticed the bite, the symptoms may be initially be mistaken for other more common infections. The signs and symptoms of Powassan virus infection may include:

  • Fever
  • Headache
  • Vomiting
  • Weakness

These non-specific symptoms may be confused with other viral infections. However, when the disease involves the nervous system then it may give rise to other symptoms such as:

  • Confusion
  • Memory problems
  • Loss of coordination resulting in speech and walking problems.
  • Seizures

Encephalitis and meningitis can be fatal. However, even if these fatal complications are overcome or avoided, there may still be permanent neurological damage. This may include recurrent headaches, muscle wasting and memory problems.

Treatment of Powassan Virus Infection

Firstly, a Powassan virus infection needs to be confirmed. This is done by isolating antibodies in the blood spread or cerebrospinal fluid. These tests should also be considered after a tick bite in high risk area, even if there are no signs or symptoms that have arisen as yet. There are no specific drugs to treat the Powassan virus infection. Instead the focus is on supportive treatment. This includes:

  • Intravenous (IV) fluid administratio.
  • Drugs to reduce brain swelling.
  • Respiratory support.

This helps to ease the signs and symptoms associated with Powassan virus and reduce or even prevent complications. Hospitalization is required for severe POW infections.

How to prevent Powassan infection?

There is currently no vaccine against the Powassan virus. Instead prevention has to focus on avoiding tick bites. These are the same preventative measures that are useful against other tick-borne diseases such as Lyme disease and Rocky Mountain spotted fever.

Read more on Lyme disease and Rocky Mountain spotted fever.

Ideally a person should avoid areas where the ticks are prevalent but this is not always possible. The following measures may instead be useful:

  • Wear protective clothing at all times when outdoors in high risk areas. This includes closed shoes, socks, long pants and long-sleeved shirt.
  • Use light-colored clothing so that ticks can be immediately spotted and removed.
  • Avoid walking in grassy and try to stay on cleared paths away from vegetation.
  • Apply insect repellant such as DEET on the skin and repellants such as permethrin on clothes. Repellant should be carried at all times in high risk areas as it only lasts for a few hours.
  • Pets should have appropriate tick repellants applied and tick repellant collars should be worn. Shampooing and bathing with appopriate insecticides is necessary as soon as possible after potential exposure.
  • Inspect clothing and the body thoroughly once indoors and immediately remove any ticks. Pay particular attention the scalp as the ticks may be hidden by hair.
  • Showering after venturing outdoors is advisable to wash off any ticks that may not have been spotted and manually removed.

References:

  1. www.cdc.gov/powassan/index.html
  2. www.webmd.com/brain/what-is-powassan

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