In conclusion, the molecular mechanisms involved in modulation of host immune systems, including TLR signaling, give us important hints on how to overcome infectious diseases caused by viruses. Pneumonia Incidence and Mortality in Mainland China: Systematic Review of Chinese and English Literature, 1985–2008 BACKGROUND: Pneumonia is a leading infectious disease killer worldwide, yet the burden in China is not well understood as much of the data is published in the non-English literature. METHODOLOGY/PRINCIPAL FINDINGS: We systematically reviewed the Chinese- and English-language literature for studies with primary data on pneumonia incidence and mortality in mainland China. Between 1985 and 2008, 37 studies met the inclusion criteria. The quality of the studies was highly variable. For children <5 years, incidence ranged from 0.06–0.27 episodes per person-year and mortality ranged from 184–1,223 deaths per 100,000 population. Overall incidence and mortality were stable or decreased over the study period and were higher in rural compared to urban areas. CONCLUSIONS/SIGNIFICANCE: Pneumonia continues to be a major public health challenge in young children in China, and estimates of pneumonia incidence and mortality vary widely. Reliable surveillance data and new prevention efforts may be needed to achieve and document additional declines, especially in areas with higher incidence and mortality such as rural settings. Despite the availability of safe and effective antibiotics and vaccines for treatment and prevention, pneumonia is a leading cause of death worldwide and the leading infectious disease killer [1, 2] . Pneumonia is the single leading cause of death globally among children under 5 years of age accounting for approximately 2 million deaths annually [2, 3] . Children in developing countries have an estimated 0.29 episodes of pneumonia per person-year, compared with 0.05 episodes per person-year in developed countries [3] .