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Influenza B outbreak among influenza-vaccinated welfare home residents in Singapore

Win MK, Chow A, Chen M, Lau YF, Ooi EE, Leo YS

Ann Acad Med Singap, 2010 Jun;39(6):448-52.
PMID: 20625620

INTRODUCTION: Outbreaks of acute respiratory illness occur commonly in long-term care facilities (LTCF), due to the close proximity of residents. Most influenza outbreak reports have been from temperate countries. This study reports an outbreak of influenza B among a highly immunised resident population in a welfare home in tropical Singapore, and discusses vaccine efficacy and the role of acute respiratory illness surveillance for outbreak prevention and control.
MATERIALS AND METHODS: During the period from 16 to 21 March 2007, outbreak investigations and active case finding were carried out among residents and nursing staff at the welfare home. Interviews and medical notes review were conducted to obtain epidemiological and clinical data. Hospitalised patients were tested for respiratory pathogens. Further genetic studies were also carried out on positive respiratory samples.
RESULTS: The overall clinical attack rate was 9.4% (17/180) in residents and 6.7% (2/30) in staff. All infected residents and staff had received influenza immunisation. Fifteen residents were hospitalised, with 2 developing severe complications. Genetic sequencing revealed that the outbreak strain had an 8.2% amino acid difference from B/Malaysia/2506/2004, the 2006 southern hemisphere influenza vaccine strain, which the residents and staff had earlier received.
CONCLUSIONS: A mismatch between the vaccine and circulating influenza virus strains can result in an outbreak in a highly immunised LTCF resident population. Active surveillance for acute respiratory illness in LTCFs could be implemented for rapid detection of antigenic drift. Enhanced infection control and other preventive measures can then be deployed in a timely manner to mitigate the effect of any outbreaks.
Fulltext Clinical features and epidemiology of chikungunya infection in Singapore

Ng KW, Chow A, Win MK, Dimatatac F, Neo HY, Lye DC, et al.

Singapore Med J, 2009 Aug;50(8):785-90.
PMID: 19710977

Chikungunya is a re-emerging mosquito-borne viral infection that has spread from East Africa to Indian Ocean islands and re-emerged in India since 2004. In Malaysia, chikungunya re-emerged after a hiatus of seven years, causing a localised outbreak in a north-western coastal town in 2006 and subsequently widespread outbreaks in 2008. Since the first local outbreak of chikungunya in Singapore in January 2008, chikungunya infections have been increasingly reported in Singapore. In this case series, five patients aged 37-62 years, with chikungunya infection confirmed in August 2008, were reported. Three of the five were male, and only one had medical comorbidities. Two had a travel history to Johor, Malaysia, where local outbreaks of chikungunya had been reported. Fever, arthralgia and rash were the most common symptoms. Fever lasted four to five days while viraemia lasted four to 11 days, persisting two to three days after defervescence in three patients. A biphasic pattern of fever was observed in two patients. Leucopenia was noted in all patients, while mild thrombocytopenia and transaminitis occurred in three of five patients. Two patients had persistent polyarthralgia at two to three weeks after the onset of symptoms. Fever, arthralgia and rash should prompt consideration of acute chikungunya in Singapore. While taking the travel history, doctors should be mindful that indigenous chikungunya cases can occur.

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