Infectious Disease Outbreaks in Competitive Sports, 2005–2010

It has been more than 5 years since Turbeville et al¹ performed a literature review identifying 59 infectious disease outbreaks or clusters among athletes in competitive sports from 1922 through May 2005. They found that herpes simplex virus (HSV) and Staphylococcus aureus were the most common pathogens reported. However, new or evolving pathogens continue to emerge, posing potentially significant risks to the health of competitors.

In 2009, the world experienced its first global influenza virus pandemic since 1968; infections occurred more commonly in younger people.^2,3 Within the last decade, community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has continued to emerge, with outbreaks and increasing rates reported in several countries.⁴ Infectious diseases commonly disrupt both an individual athlete's participation in sports and a team's ability to perform.

It is clearly important that the nature of outbreaks of infection among athletes are documented and delineated so that preventive measures may be undertaken. In an ever-changing environment, a review that spanned more than 80 years may not provide an accurate reflection of the pathogens currently of concern among sports competitors.¹ With this 5-year update of infectious disease outbreaks in sports, our goal was to provide a current picture of the pathogens involved in published outbreaks in athletes.

METHODS

We used similar methods to those used by Turbeville et al¹ to compare results. Search terms with the key words infection, outbreak, and sport were used to search the PubMed database from May 2005 through November 2010 for relevant English-language articles. All reports of infectious disease outbreaks or clusters in competitive sports were included in this review, regardless of methodologic quality.¹ We included additional studies from the reference list of articles and those that we found incidentally if they were deemed appropriate. Newspaper or magazine outbreak reports, food-borne outbreaks, outbreaks associated with leisure pursuits, and outbreaks not clearly associated with competitive sports were not included.

RESULTS

We found 24 relevant articles (Table). Of these, 19 were solitary reports of an outbreak in a single sport ^5–23; 3 (including 2 from Juntendo University^24,25) addressed a tinea epidemic due to Tricophyton tonsurans among combat-sport (mainly judo, although one also included wrestlers²⁶) competitors in Japan ^24–26; 1 reported on a single measles virus outbreak involving competitors in 2 sports;hairsp²⁷; and 1 discussed the importance of sentinel surveillance sites in high school athletic departments to monitor outbreaks of CA-MRSA across a variety of sports.²⁸ When we excluded this latter study from analysis (because its main focus was not a specific outbreak) and counted the 3 articles on the tinea outbreak among combat-sport competitors in Japan as a single outbreak, a total of 21 outbreaks or clusters were reported in the time period. Nine outbreaks (43%) were reported in North America (United States = 8, Canada = 1), 8 (38%) in Asia (Japan = 4, Turkey = 2, Iran = 2), and 4 (19%) in Europe (Germany = 1, Belgium = 1, France = 1, Slovenia = 1). Twelve of the outbreaks (57%) involved high school or collegiate competitors. Most outbreaks occurred in non–weapon-based combat sports (wrestling or judo: n = 7 [33%]) or American football (n = 5, 24%). Only 1 outbreak was reported in each of the following sports: adventure racing, baseball, basketball, mountain biking, rugby, soccer, swimming, and triathlon. One outbreak was facilitated by both a marathon race and a kendo (Japanese fencing) event.²⁷

Table.  Published Reports on Infectious Disease Outbreaks in Competitive-Sport Athletes, May 2005–November 2010

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The most common pathogens responsible for the outbreaks were MRSA (n = 7, 33%) and tinea (trichophytosis; n = 6 [29%]). Six of the 7 MRSA outbreaks were due to CA-MRSA; 1 report¹⁴ did not include typing studies, but the nature of the outbreak suggested that it was also due to CA-MRSA. All of the CA-MRSA outbreaks were reported in US high school or collegiate competitors except for 1 among soccer players in Slovenia.²² Among American football players, MRSA was the pathogen responsible for all outbreaks reported. Another pathogen was Leptospira spp. (n = 2 [10%]), whereas Campylobacter jejuni, Cryptosporidium spp., echovirus 30, HSV, measles virus, and Streptococcus pyogenes accounted for 1 (5%) each. In the 2 reports (10%) that involved echovirus 30 and measles virus, the outbreak spread beyond the bounds of the sporting environment and into the community.^9,27

Skin and soft tissue was by far the most common site of infection (n = 15 [71%]). Other sites of infection included systemic involvement (n = 3 [14%]), the gastrointestinal tract (n = 2 [10%]), and the central nervous system (n = 1 [5%]). All transmissions were spread person to person, directly or indirectly, or via common-source exposure with examples similar to those Turbeville et al¹ described. No vector-borne or blood-borne outbreaks were reported. Interestingly, we did not find any reported outbreaks of pandemic H1N1 (2009) influenza among competitors.

CONCLUSIONS

Infectious disease outbreaks are being increasingly reported in the literature, with at least 21 reports identified since the review by Turbeville et al.¹ More than half (57%) of these occurred at the high school or collegiate level. The most predominant pathogen was MRSA (n = 7 [33%]), followed by tinea (n = 6 [29%]). In comparison, Staphylococcus aureus (both methicillin susceptible and methicillin resistant) and HSV were the most common pathogens in the Turbeville et al study, each accounting for 13 (22%) of the 59 reported outbreaks, whereas tinea was responsible for 8 outbreaks (14%).¹ Outbreaks of CA-MRSA in competitive sports remain rare outside the United States. The majority of outbreaks (71%) involved the skin and soft tissue, supporting the Turbeville et al¹ findings that skin infections accounted for 56%, and occurred in close-contact sports. Surprisingly, common community outbreak pathogens, such as influenza virus and norovirus, have received little attention in the sporting literature, with no outbreaks of these organisms reported in competitive athletes in the last 5 years.

We surmise that the changes in reported pathogens between this study and the previous study likely reflect the emergence of CA-MRSA as a significant community pathogen in the United States but are also the result of some reporting and publication bias.