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Recommendations: Patients with Molluscum Contagiosum and Swimming Pool Safety
Background
Concern for potential transmission of molluscum contagiosum virus via swimming pools and/or swimming pool-related paraphernalia (e.g., towels, kick boards) is a recurring issue for parents, teachers, and coaches and for health care and public health professionals.
Several investigations have centered around increased cases of molluscum contagiosum among children in the context of recreational swimming. Although biologically plausible, epidemiologic studies have failed to demonstrate conclusively how, or under what circumstances, recreational swimming might facilitate molluscum contagiosum virus transmission. In fact, some studies failed to find an association between swimming pool use and virus transmission altogether. (1) Several studies that did implicate swimming pool use with molluscum neglected to adequately account for other factors that could introduce bias or influence virus transmission, such as the age of the subjects, their participation in other forms of physical activity (i.e., contact sports), and their shared use of potential fomites (towels, kick boards). (2-4)
An additional issue complicating the interpretation of molluscum transmission studies is the widely variable incubation time from infection to development of molluscum lesions (range, 2 weeks to 6 months), making the association between the event and lesion difficult to confirm.
It remains unclear whether contact with contaminated fomites is important (i.e., kick boards, towels) or whether swimming in potentially contaminated water alone is sufficient for virus transmission. It is conceivable that maceration of the molluscum contagiosum lesions following water submersion facilitates person-to-person contact or fomite transmission. Current culture techniques do not support the growth of molluscum contagiosum virus, therefore, many of these questions can not be directly answered. Further research is necessary to better characterize molluscum contagiosum virus viability in pool environments. These studies may include the use of novel culture techniques (5) and surrogate markers for viral replication (mRNA transcription). (6)
Recommendations
Since molluscum contagiosum may be found in up to 10% of the pediatric population at any given time (7), the decision to prohibit children with molluscum contagiosum from swimming in public pools should be given careful consideration. Exclusion may interfere with much needed physical and social outlets as well as create social stigma.
If such a policy were instituted, the diagnosis of molluscum contagiosum should be made by a health care provider and all participating children should be subject to the same screening physical exam. Such screening could be incorporated into annual sports/camp physicals. A thorough skin examination should already be performed during these physicals for other conditions such as atopic dermatitis. Thus, identification of molluscum lesions should not pose an undue burden during this process.
Covering visible lesions with a watertight bandage, disposing of all bandages at home or in a health care setting, using good hand hygiene, ensuring that towels are not shared, and providing individual kick boards are all reasonable interventions to help prevent the spread of molluscum contagiosum and other infections acquired through contact exposures (e.g., methicillin-resistant Staphylococcus aureus). Additionally, thorough disinfection and drying of kickboards should reduce the likelihood of molluscum contagiosum transmission.
Studies investigating
surfaces contaminated with other pox viruses (e.g., vaccinia) indicate
that household bleach solutions (containing at least 200 mg/L of sodium hypochlorite),
iodophors, and other Environmental Protection Agency-registered surface
disinfectants are effective decontaminants if the manufacturer’s recommendations
for use-dilution (i.e., concentration), contact time, and care in handling
are closely followed. Because the molluscum contagiosum virus has similar viral
envelope properties, it is reasonable to conclude that these disinfectants
would be effective against the molluscum contagiosum virus. These disinfectants
are the only alternative at this time (see table 1 in Guide F Environmental
Control of Smallpox http://www.bt.cdc.gov/agent/smallpox/response-plan/files/guide-f.pdf 
).
Children with open sores or skin breaks should avoid pool use because
of other infectious risks (bacterial and mycobacterial infections). This
general recommendation should remain unchanged for children with molluscum
contagiosum.
References
1. Oren B, Wende SO. An outbreak of molluscum contagiosum in a kibbutz. Infection.
1991;19(3):159-161.
2. Niizeki K, Kano O, Kondo Y. An epidemic study of molluscum contagiosum:
relationship to swimming. Dermatologica. 1984;169:197-198.
3. Castilla M. Molluscum contagiosum in children and its relationship to attendance
at swimming-pools: an epidemiological study. Dermatol. 1995;191:165.
4. Choong KY, Roberts LJ. Molluscum contagiosum, swimming and bathing: a clinical
analysis. Australas J Dermatol. 1999;40:89-92.
5. Dai NT, Yeh MK, Liu DD, et al. A co-cultured skin model based on cell support
membranes. Biochem Biophys Res Commun. 2005;329(3):905-908.
6. Howell MD, Jones JF, Kisich KO, Streib JE, Gallo RL, Leung DY. Selective
killing of vaccinia virus by LL-37: implications for eczema vaccinatum. J Immunol.
2004;172(3):1763-1767.
7. Gottlieb SL, Myskowsi PL. Molluscum contagiosum. Int J Dermatol. 1994;33:453-461.
Links
Addition information is available from the following Websites:
Pool Safety
(from Bernalillo County Environmental Health Office, New Mexico)
Six "PLEAs" For
Healthy Swimming: Protection Against Recreational Water Illnesses (RWIs)
(on CDC Healthy Swimming site)