The Winter Olympic Games kick off tomorrow in Pyeongchang, South Korea. With huge crowds expected to converge in the small city over the next two weeks, reports of local transmission of several diseases—including norovirus and seasonal influenza—are putting South Korean health officials and Olympic organizers on high alert. The presence of large crowds in sporting venues, cold winter temperatures, and close living quarters at the Olympic Athletes Village are conducive to the spread of communicable diseases. This has sparked fears that these individuals will become ill and transmit diseases upon returning to their home countries, potentially sparking a wider epidemic or pandemic.

Despite the risks to athletes, spectators, and residents alike, previous outbreaks at sporting competitions and other mass gathering events suggest a rather low likelihood of the Olympics leading to a major outbreak. Nevertheless, health officials will need to act swiftly to implement public health measures to ensure minimal disruption to the Winter Games and prevent a worsening of the public health situation. Below we address some of the ongoing potential infectious disease risks facing the 2018 Winter Olympics.

Norovirus Outbreak

One of the biggest infectious disease threats to the 23rd Winter Olympics is norovirus, a highly contagious gastrointestinal disease that usually spreads through the ingestion of contaminated food or drink. On Tuesday, Olympic officials reported that 41 security guards in Pyeongchang fell ill with norovirus. As a result, the South Korean military deployed 900 military personnel to Olympic venues to replace all 1,200 civilian security guards, who were quarantined following the outbreak. As of today (February 8), a total of 128 cases have been confirmed, including not only security staff but other Olympic staff members and members of the media.

Due to its highly contagious nature, norovirus is the leading cause of illness from contaminated food in the US, leading to approximately 56,000-71,000 hospitalizations per year nationwide. Globally, norovirus infects some 685,000 people and leads to approximately 50,000 deaths in children annually, especially in developing nations. Symptoms include diarrhea, vomiting, fever, headaches, and dehydration, and persons 65 years and over and children under 5 are at the highest risk for norovirus-associated death and medical care visits. While reasonably healthy individuals with access to basic health services are typically expected to make a full recovery, any Olympic athlete unfortunate enough to contract the disease would likely find it difficult to compete in the Winter Games.

In response to the outbreak, the International Olympic Committee said they are aggressively moving to prevent the virus from disrupting the festivities. In addition to quarantining affected security staff, organizers are investigating food chain safety and raising awareness among the public, including the distribution of informational leaflets detailing steps for preventing and treating norovirus. The source of the outbreak has not yet been identified.

Seasonal Influenza

A second disease threat at the Olympics is seasonal influenza. As previously reported by Outbreak Observatory, the 2017-18 flu season in the US has been particularly severe due to a variety of factors. The Korean Peninsula is likewise battling a serious flu epidemic. The WHO confirmed 81,640 cases of influenza in North Korea between December 1, 2017 and January 16, 2018, while South Korea has reported 1,250 cases over a similar timeframe. The H1N1 flu strain is dominant on the Korean Peninsula, whereas the H3N2 strain has accounted for more than 80% of cases in the US. Both strains are currently circulating globally.

While North Korea’s public health response is unclear, it has requested international assistance from the WHO and UNICEF, including vaccines and medical equipment, and the International Federation of Red Cross and Red Crescent Societies (IFRC) is reportedly planning to send $270,000 in emergency aid. While North Korea’s inclusion in the games, including its participation in a combined Korean women’s ice hockey team, does provide potential for North Korean athletes and visitors to spread the virus to others in South Korea, its small Olympic delegation and relatively few spectators will likely not have a major impact on disease spread.

Of greater concern, however, is the likelihood that the large numbers of tourists, athletes, and residents converging on Pyeongchang will contribute to the ongoing spread of seasonal influenza in South Korea and potentially elsewhere when everyone returns home. The WHO reports that the flu season is raging in East Asia, noting that “high levels of illness indicators and influenza activity were reported in most of the countries [in the region].” The densely crowded Olympic Athletes Village may be at even higher risk of spreading influenza. A prospective study conducted during the 2002 Salt Lake City (USA) Winter Olympics and Paralympics revealed that influenza A/B was diagnosed in 36 of 188 patients who reported to the Olympic Village medical clinic. Athletes were found to represent 36% of all flu patients despite accounting for only 24% of those screened for influenza infection. A low rate of flu vaccination among athletes may have contributed to the high number of cases. Effective surveillance, contact tracing, and treatment in the form of oseltamivir ultimately helped to mitigate the spread of the virus.

Avian Influenza

In addition to seasonal influenza, South Korea’s Ministry of Agriculture, Food, and Rural Affairs announced the presence of H5N6 avian influenza at several chicken farms located about 80 miles from Pyeongchang. Avian influenza comprises several highly virulent strains of influenza primarily transmitted to humans after direct exposure to infected poultry. The H5N6 strain does not typically exhibit human-to-human transmission, but the case fatality rate is estimated at 68.75% in humans. The disease must be closely monitored for genetic changes that could enable it to develop the capability for sustained human-to-human transmission. China has reported 16 laboratory-confirmed human cases of H5N6 since 2014, but according to the WHO, human cases of H5N6 have never been detected in South Korea. South Korea is carefully monitoring and inspecting local poultry farms for H5N6 and has culled some half a million chickens in recent weeks. Fortunately, Olympic athletes, media, and spectators are unlikely to have direct contact with affected poultry, so avian influenza is not expected to be a major health risk over the next several weeks.

Outbreak Risks?

As previously mentioned, the Olympic Games and other mass gathering events can pose special public health risks. A recent example includes fears of the Zika virus during the 2016 Summer Olympics in Rio de Janeiro, Brazil, which prompted calls by some experts for the games to be cancelled. In August 2017, an outbreak of norovirus at the World Athletics Championships in London, UK led several athletes to withdraw from that competition. Measles outbreaks occurred during the World Cup in South Africa in 2010 and the Special Olympics in Minneapolis, Minnesota (USA) in 1991. Additionally, local measles cases in Arizona (USA)—linked to the Disneyland outbreak—prompted concern leading up to Super Bowl XLIX (2015), but no associated transmission was detected. Similar concerns have revolved around non-sports mass gathering events—most notably the annual Hajj pilgrimage in Mecca, Saudia Arabia which attracts about 7 million pilgrims each year—such as fears of outbreaks of yellow feverMERS, and other diseases.

The WHO defines mass gathering events as those “attended by a sufficient number of people to strain the planning and response resources of a community, state or nation.” According to a 2013 study on mass gatherings, globalization and increasing rates of travel may increase the likelihood that these events may “facilitate the spread of communicable diseases, particularly emerging infectious diseases;” however, this spread “can be controlled through effective vigilance and planning.”

For example, statistical models showed that the risk of tourists contracting dengue fever at the 2014 World Cup in Brazil—despite high local transmission rates—was estimated to be small. This was due, in part, to the short duration of time tourists were expected to spend in the country as opposed to any specific public health response taken on the part of the government or event officials. On the contrary, other case studies reveal that enhanced surveillance measures and infection control strategies implemented by public health officials can, in fact, reduce the risk of transmission and facilitate a rapid public health response. For example, the implementation of an H1N1 preparedness plan by the Saudi Arabia Ministry of Health is believed to have mitigated the spread of the H1N1 influenza pandemic during the Hajj in 2009. More recently, a 2017 report by the European Centers for Disease Control—while noting the potential for the spread of outbreaks such as cholera, polio, yellow fever, measles, and seasonal influenza at the 2017 Hajj pilgrimage—concluded that the overall risk of acquiring infectious diseases was “considered to be low.”

While the health risks posed by mass gathering events must be assessed on a case-by-case basis, these reports suggest that, while the risks posed by infectious diseases are very real, they are often lower than what might be expected and can be effectively managed through appropriate public health preparedness and response efforts. Similarly, adequate public health interventions at the Winter Olympic Games in South Korea can help to control the recent outbreaks of norovirus, seasonal influenza, and avian influenza and avert a wider public health crisis. This will go a long way to ensuring that the only Olympic Fever is due to global goodwill and the excitement of competition.


Photo: The Olympic flag flies over competition at the 1996 Summer Olympics in Athens, Georgia (USA).

Photo courtesy of CDC/Dr. Edwin P. Ewing, Jr.

Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly to allow others to learn from these experiences in order to improve global outbreak response capabilities.