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Verrucas and games

Bandoliers GP callers do ask some hard questions. One, faced with the problem of a schoolgirl patient not being allowed to take swimming in school because she had a verruca, challenged Bandolier to find any evidence that there was risk of infection. Well, there is some. Bandolier could only find one paper which seemed to address this question, published in the US GP journal Family Practice in 1995 [1].

Plantar warts

Plantar warts (verrucae plantaris) are usually caused by type 1 human papillomavirus (HPV). The route of infection is thought to be through an abrasion or cut, and the virus attacks the granulosum and keratin layers of the skin. Prevalence of plantar warts in a 1955 study of 13,000 East Anglian schoolchildren was 6.5 per 1,000, with a peak incidence at 13 for girls and 14 and 15 for boys. A US prevalence study in 1953, with 2,300 children studied in Illinois, was higher at 45 per 1,000.

Study of verruca infection

146 adolescents in Nashville, Tennessee, aged 10 to 18 years, were recruited from a local school (on the day of the study 80 of 150 children asked to participate agreed) and all the 66 members of a swimming club under 19 years. The two groups used different public changing rooms, but only the swimming club members used a public shower. A standard protocol was used by physicians to collect information on use of public showers, use of shower sandals when bathing, sport participation, and history of verruca. Diagnosis of plantar wart was made on physical examination using the criteria of a well circumscribed cauliflower appearance and texture on palpation. All positive cases were examined by one doctor.


Nineteen cases of plantar warts were found in the 146 adolescents studied - an incidence of 13%. Only 1 of 80 schoolchildren had a verruca (1%). By contrast, 18 of 66 swimming club members of the same age who used communal showers had a verruca (27%).
Previous infection with verruca was higher among those with a current infection (67%), compared with 27% of those not currently infected reporting previous infection. Half of shower room users reported previous infection, compared with 16% in those who did not use a communal shower.


In terms of levels of evidence, this study comes fairly low on the scale. The main problems are that the numbers are small and from two distinct populations. The two groups used different public changing rooms, but only the swimmers used public showers. Is it right to ascribe the huge difference in verruca infection (27% versus 1%) to the public showers? To be fair, the author criticises these aspects of the study, but balances this against a literature search which (though limited in yield) shows at least one study which excludes swimming pools themselves as sources of infection. This does not alter the fact that there could be some other extraordinary factor in this swimming club which has led to the high rate of verruca infection. On balance, with a large pinch of salt, this is a believable result until proven wrong. Perhaps the surprising thing is that there appears to be so little literature for so common a problem, and one which causes parents and GPs so much trouble.

The truth is out there

Is there anyone out there who knows of more or better information, is doing a study, or is keen to do one? The truth is out there, but it needs to be gathered in. Should this be the first Bandolier epidemiological survey?


  1. LW Johnson. Communal showers and the risk of plantar warts. Journal of family Practice 1995 40:136-8.

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