Emergence of influenza B/Victoria in the Micronesian US-affiliated Pacific Islands, spring 2019

• Authors: Stephanie O'Connor, Emory University; Thane W Hancock, Centers for Disease Control and Prevention, Atlanta; Estelle Ada, Guam Department of Public Health & Social Services; Edlen Anzures, Ministry of Health Marshall Islands; Christine Baza, Guam Department of Public Health & Social Services; Annette L Aguon, Guam Department of Public Health & Social Services; Doris Cruz, Commonwealth of the Northern Mariana Islands; Eliaser Johnson, Department of Health and Social Affairs, Pohnpei, Federated States of Micronesia; Allan Mallari, Guam Department of Public Health & Social Services; Jill A McCready, Ministry of Health Marshall Islands; Jack Niedenthal, Ministry of Health Marshall Islands; Ann Pobutsky, Guam Department of Public Health & Social Services; Anne Marie Santos, Guam Department of Public Health & Social Services; Jose Villagomez Santos, Commonwealth of the Northern Mariana Islands; Jeremy Sasamoto, Commonwealth of the Northern Mariana Islands; Portia Tomokane, Commonwealth of the Northern Mariana Islands; Warren Villagomez, Commonwealth of the Northern Mariana Islands; Paul White, Commonwealth of the Northern Mariana Islands
• Journal Title: Western Pacific surveillance and response journal : WPSAR
• Volume: Volume 12, Number 4
• Publisher: WHO WPRO | 2021-10-01, Pages 1-9
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.5365/wpsar.2021.12.4.706
• Subjects: Health Sciences, Epidemiology; Health Sciences, Public Health
• Keywords: Adult; Humans; Influenza, Human; Micronesia; Native Hawaiian or Other Pacific Islander; Pacific Islands; Seasons; United States; Young Adult

Abstract

Data collected through routine syndromic surveillance for influenza-like illness in the Micronesian United States-affiliated Pacific Islands highlighted out-of-season influenza outbreaks in the spring of 2019. This report describes the data collected through the World Health Organization's Pacific Syndromic Surveillance System for the Commonwealth of the Northern Mariana Islands (CNMI), Guam, the Federated States of Micronesia (FSM) and the Republic of the Marshall Islands (RMI). Compared with historical data, more cases of influenza-like illness were observed in all four islands described here, with the highest number reported in Guam in week 9, CNMI and FSM in week 15, and RMI in week 19. The outbreaks predominantly affected those aged < 20 years, with evidence from CNMI and RMI suggesting higher attack rates among those who were unvaccinated. Cases confirmed by laboratory testing suggested that influenza B was predominant, with 83% (99/120) of subtyped specimens classified as influenza B/Victoria during January-May 2019. These outbreaks occurred after the usual influenza season and were consistent with transmission patterns in Eastern Asia rather than those in Oceania or the United States of America, the areas typically associated with the United States-affiliated Pacific Islands due to their geographical proximity to Oceania and political affiliation with the United States of America. A plausible epidemiological route of introduction may be the high levels of international tourism from Eastern Asian countries recorded during these periods of increased influenza B/Victoria circulation. This report demonstrates the value of year-round surveillance for communicable diseases and underscores the importance of seasonal influenza vaccination, particularly among younger age groups.