Influenza in Refugees on the Thailand–Myanmar Border | CDC EID

Volume 16, Number 9–September 2010
Research
Influenza in Refugees on the Thailand–Myanmar Border, May–October 2009
Paul Turner, Claudia L. Turner, Wanitda Watthanaworawit, Verena I. Carrara, Bryan K. Kapella, John Painter, and François H. Nosten
Author affiliations: Shoklo Malaria Research Unit, Mae Sot, Thailand (P. Turner, C.L. Turner, W. Watthanaworawit, V.I. Carrara, F.H. Nosten); Mahidol–Oxford Tropical Medicine Research Unit, Bangkok, Thailand (P. Turner, C.L. Turner, W. Watthanaworawit, V.I. Carrara, F.H. Nosten); University of Oxford, Oxford, UK (P. Turner, C.L. Turner, F.H. Nosten); and Centers for Disease Control and Prevention, Atlanta, Georgia, USA (B.K. Kapella, J. Painter)

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Abstract
We describe the epidemiology of influenza virus infections in refugees in a camp in rural Southeast Asia during May–October 2009, the first 6 months after identification of pandemic (H1N1) 2009 in Thailand. Influenza A viruses were detected in 20% of patients who had influenza-like illness and in 23% of those who had clinical pneumonia. Seasonal influenza A (H1N1) was the predominant virus circulating during weeks 26–33 (June 25–August 29) and was subsequently replaced by the pandemic strain. A review of passive surveillance for acute respiratory infection did not show an increase in acute respiratory tract infection incidence associated with the arrival of pandemic (H1N1) 2009 in the camp.
Pandemic (H1N1) 2009 emerged in April 2009 and subsequently spread around the globe. The World Health Organization issued a pandemic declaration on June 11, 2009 (1,2). By October 25, 2009, >440,000 laboratory-confirmed cases, including >5,700 deaths, had been reported to WHO (3). The first case of pandemic (H1N1) 2009 infection was diagnosed in Thailand on April 28, 2009, and subsequently the virus was detected in all provinces. The Thailand Ministry of Public Health reported 27,639 confirmed cases and 170 deaths as of October 10, 2009 (4). Myanmar (Burma) reported its first confirmed case of pandemic (H1N1) 2009 infection during the week beginning July 5, 2009, and by the end of October 2009 had reported <100 confirmed cases with no deaths (5). Although most infections caused by this new virus have been mild, severe disease has been reported, particularly in young adults (6).

Data regarding the effect of influenza in rural areas of the developing world are scarce, as are etiologic data from refugee populations (7–9). A recent review of published reports from Southeast Asia concluded that influenza infection may be identified in up to 26% of outpatients with febrile illness and in 14% of hospitalized patients with pneumonia (10). In Thailand, seasonal influenza virus activity peaks during the rainy season (June– September), with smaller peaks occurring during the cold months (January and February) (11). Incidence of influenza infections in Thailand was 64–91 cases/100,000 persons per year during 1999–2002; the influenza-related hospitalization rate was 21/100,000 persons during 1999 (11). Influenza infections in Myanmar are also seasonal; cases are documented predominantly in the rainy season (May–October) (12–14). Incidence data for influenza virus infections in Myanmar are not readily available.

Of 15.2 million refugees worldwide, approximately one third live in camps (15). These refugees often live in crowded conditions and have contact with populations from the host country and the country of origin, where public health infrastructure and surveillance may be poor (16,17).

Approximately 150,000 refugees from Myanmar are housed in several camps on the Thailand–Myanmar border. Maela Temporary Shelter (Maela, Thailand) is the largest of these camps, with a population of >40,000, predominantly of the Karen ethnic group, housed in a 4-km2 area (18). This camp is located in the hills adjoining the Myanmar border, »500 km northwest of Bangkok, and has been in operation since 1984. Primary health and sanitation services are provided by nongovernmental organizations. A field hospital with an inpatient area and 2 outpatient clinics provide free healthcare to the camp’s population, who do not have access to healthcare facilities outside of the camp. Acute respiratory infection (ARI) is a common cause of illness in Maela, but the proportion of infections caused by influenza viruses is unknown. Seasonal influenza vaccinations and antiviral medicines are not readily available in the camp or the surrounding community.

In 2007, the US Centers for Disease Control and Prevention (CDC) and Shoklo Malaria Research Unit (www.shoklo-unit.com) established a laboratory-enhanced ARI surveillance system in Maela. Pilot data were obtained during late 2007, and formal surveillance began in 2008 with a 2-day-per-week patient review in the outpatient department of Aide Medicale Internationale Hospital. In 2009, daily patient reviews were carried out in outpatient (from January 2009) and inpatient (from April 2009) departments. We report the results of this surveillance during May–October 2009 and describe the impact of the current influenza pandemic in this rural refugee population. Data from our surveillance activities in 2008, as well as passively collected ARI incidence data, are included for comparison.

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Influenza in Refugees on the Thailand–Myanmar Border | CDC EID