Influenza associated mortality in the subtropics and tropics: Results from three Asian cities

Abstract

Influenza has been well documented to significantly contribute to winter increase of mortality in the temperate countries, but its severity in the subtropics and tropics was not recognized until recently and geographical variations of disease burden in these regions remain poorly understood. In this study, we applied a standardized modeling strategy to the mortality and virology data from three Asian cities: subtropical Guangzhou and Hong Kong, and tropical Singapore, to estimate the disease burden of influenza in these cities. We found that influenza was associated with 10.6, 13.4 and 8.3 deaths per 100,000 population in Guangzhou, Hong Kong and Singapore, respectively. The annual rates of excess deaths in the elders were estimated highest in Guangzhou and lowest in Singapore. The excess death rate attributable to A/H1N1 subtype was found slightly higher than the rates attributable to A/H3N2 during the study period of 2004-2006 based on the data from Hong Kong and Guangzhou. Our study revealed a geographical variation in the disease burden of influenza in these subtropical and tropical cities. These results highlight a need to explore the determinants for severity of seasonal influenza.

Mortality burden from seasonal influenza and 2009 H1N1 pandemic influenza in Beijing, China, 2007‐2013

“…3, 4, 5, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 Notably, our study observed that influenza B caused the highest burden (20.5 [CI 14.2‐34.9] per 100 000) when influenza B virus predominated in 2007/2008. This mortality pattern is consistent with those described in studies conducted by China CDC and Guangzhou CDC,3, 5 but differs from studies conducted in other regions such as Hong Kong,14 Singapore,16 Thailand,17 United States,18, 19 and New Zealand,23 where the highest death rates were associated with influenza A(H3N2).…”

Prospective Epidemiological Evaluation of Seasonal Influenza in All Elementary Schoolchildren in Matsumoto City, Japan, in 2014/2015

“…Third, because the study population included only elementary schoolchildren, children in kindergarten and junior high school were not evaluated. Fourth, influenza epidemics, even during the same season, differ among countries, suggesting that geography usually affects influenza epidemics during large-scale evaluations (31,32). Influenza epidemics are also affected by weather-associated factors, including humidity (33).…”

Differing Epidemiological Dynamics of Influenza B Virus Lineages in Guangzhou, Southern China, 2009-2010

“…Vaccine coverage is still relatively low in Guangzhou, with an estimated 13 vaccine doses used per 100 population (45), while a pediatric study reported a 6.5% vaccination rate for pandemic H1N1/09 in a boarding school (46). The vaccine is administered around October-December in anticipation of the Northern Hemisphere winter influenza season, peaking in January or February.…”