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Causes of verrucas

By Dr Ananya Mandal, MD

Verrucas (verrucae) or plantar warts are small, rough, raised or flattened lumps that occur over the pressure areas of the feet. These are commonly caused by infections with different strains of the human papilloma virus (HPV).

The virus may be isolated from the skin cells of verrucae. Around half of these disappear on their own in a year. Two thirds of the verrucae persist for at least two years and disappear without therapy. The other one third persists for more than 2 years and is resistant to therapy.

Who gets verrucas?

Most people will get verrucae at some point in their lives and women get it slightly more commonly than men. The peak incidence is seen in children with 4 to 5% affected but infants are usually spared. 1-5

Causative organism of verrucas

There are over 100 different types or strains of HPV that have been identified. Different strains of HPV are responsible for causing different types of warts. For example, types 1 and 2 are commonly implicated for causes plantar warts or verrucae. Type 4 is also found in some cases.

The virus invades the top most layer of the skin called the epithelium and starts replicating within these epithelial cells. This may lead to multiplication of the cells and formation of plaques or papules or the flattened warts. The incubation period is often up to a year. This means from the time of invasion of the virus to formation of the warts, the time taken may be up to a year. HPV is highly contagious.

Method of spread of verrucas

HPV from the verrucae may spread through close skin-to-skin contact. These warts are contagious as long as they are present on the body as they contain the live virus within them. Sometimes the virus may also spread by sharing objects like towels, socks, shoes, baths and community showers with infected persons.

In addition, those who have wet, soft, ulcerated or sore skin of the feet are more likely to get the infection than those with dry and intact skin of the feet.

The virus particularly spreads to more than one part of the same individual’s body if they scratch, itchy, bite (nails with finger warts), suck (fingers with warts) or shave (face or the legs with warts) over the warts. This is called auto-inoculation. This trauma usually leads the warts to break up and bleed and helps spread the virus to other parts of the body or to other individuals.

Despite spread due to sharing community showers or baths and pools, the National Curriculum suggests that all children should learn to swim as it helps to prevent death from drowning and risk of verrucae should not deter children from acquiring this skill.

Risk factors

Some individuals are more at risk of getting verrucae. These include certain professions like butchers, engineers, office workers etc. Those who have low immunity like in people with AIDS or those taking immunity suppressing medications after a transplant are at a risk of verrucae. In fact many people get warts (plantar or other types) after a kidney transplant. Diabetics are at a risk of these warts and have difficulty in preventing a recurrence after cure.

Reviewed by , BA Hons (Cantab)

Further Reading

Last Updated: Sep 4, 2012

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