Influenza and Mass Gathering | CDC EID

EID Journal Home > Volume 16, Number 5–May 2010

Volume 16, Number 5–May 2010
Research
Influenza Outbreaks during World Youth Day 2008 Mass Gathering
Christopher C. Blyth,1 Hong Foo, Sebastiaan J. van Hal, Aeron C. Hurt, Ian G. Barr, Kenneth McPhie, Paul K. Armstrong, William D. Rawlinson, Vicky Sheppeard, Stephen Conaty, Michael Staff, and Dominic E. Dwyer, on behalf of the World Youth Day 2008 Influenza Study Group2
Author affiliations: Westmead Hospital, Sydney, New South Wales, Australia (C.C. Blyth, H. Foo, S.J. van Hal, K. McPhie, D.E. Dwyer); WHO Collaborating Centre for Influenza Reference and Research, Melbourne, Victoria, Australia (A.C. Hurt, I.G. Barr); New South Wales Department of Health, Sydney (P.K. Armstrong); Prince of Wales Hospital, Sydney (W.D. Rawlinson); Sydney West Public Health Unit, Paramatta, New South Wales, Australia (V. Sheppeard); Sydney South West Public Health Unit, Camperdown, New South Wales, Australia (S. Conaty); and North Sydney Central Coast Public Health Unit, Hornsby, New South Wales, Australia (M. Staff)

Suggested citation for this article

Abstract
Influenza outbreaks during mass gatherings have been rarely described, and detailed virologic assessment is lacking. An influenza outbreak occurred during World Youth Day in Sydney, Australia, July 2008 (WYD2008). We assessed epidemiologic data and respiratory samples collected from attendees who sought treatment for influenza-like illness at emergency clinics in Sydney during this outbreak. Isolated influenza viruses were compared with seasonal influenza viruses from the 2008 influenza season. From 100 infected attendees, numerous strains were identified: oseltamivir-resistant influenza A (H1N1) viruses, oseltamivir-sensitive influenza A (H1N1) viruses, influenza A (H3N2) viruses, and strains from both influenza B lineages (B/Florida/4/2006-like and B/Malaysia/2506/2004-like). Novel viruses were introduced, and pre-WYD2008 seasonal viruses were amplified. Viruses isolated at mass gatherings can have substantial, complex, and unpredictable effects on community influenza activity. Greater flexibility by public health authorities and hospitals is required to appropriately manage and contain these outbreaks.
Influenza is caused by a highly infectious respiratory virus with the potential to rapidly spread in susceptible hosts. Influenza outbreaks have frequently been described in populations such as residents of nursing care facilities (1,2), residential schools or colleges (3,4), prisons (5), military facilities (6), and other enclosed communities (7).

Mass gatherings pose complex and unique challenges to public health and medical services. Because populations are increasingly mobile, and more able to attend large gatherings, the risk for outbreaks of influenza and other infectious diseases among a susceptible population has increased, and a substantial responsibility is placed on health services if outbreaks occur. Despite this situation, influenza outbreaks during mass gatherings have rarely been described (8–10), and reports have not included results of detailed virologic testing. Furthermore, the effects of outbreak strains on local influenza epidemiology have not been assessed.

During World Youth Day (WYD2008) celebrations, 223,000 predominately young pilgrims from 170 countries attended a series of mass religious gatherings from July 15 to July 20, 2008, in Sydney, New South Wales (NSW), Australia. At the end of the week, an outdoor evening vigil with >200,000 participants preceded the final mass presided over by Pope Benedict XVI. This mass was attended by an estimated 400,000 persons (11). Approximately 100,000 pilgrims were given accommodation in sporting facilities, schools, and community centers, where temporary floor mats and blankets were provided and other facilities were shared. The largest site of accommodation, the Sydney Olympic Park site, provided lodging for as many as 12,000 pilgrims each night. Pilgrims remained housed overnight at the allocated accommodation sites and attended numerous outdoor religious gatherings during the day with other pilgrims. Many pilgrims traveled in Australia and New Zealand before and after the WYD2008 celebrations, visiting major cities and rural areas.

We describe the epidemiologic and virologic features of an influenza outbreak predominantly among young adults during WYD2008 celebrations. These data provide insight into the complexity of influenza outbreaks during mass gatherings and their effects on the community at large. The insights gained should guide plans for mass events, particularly when held during periods of peak influenza activity.

open here to see the full-text: (large)
Influenza and Mass Gathering | CDC EID

Suggested Citation for this Article
Blyth CC, Foo H, van Hall SJ, Hurt AC, Barr IG, McPhie K, et al. Influenza outbreaks during World Youth Day 2008 mass gathering. Emerg Infect Dis (serial on the Internet). 2010 Apr [date cited]. http://www.cdc.gov/EID/content/16/5/809.htm

DOI: 10.3201/eid1605.091136