A novel influenza A (H1N1) virus has spread rapidly across the globe. Judging its pandemic potential is difficult with limited data, but nevertheless essential to inform appropriate health responses. By analyzing the outbreak in Mexico, early data on international spread, and viral genetic diversity, we make an early assessment of transmissibility and severity. Our estimates suggest that 23,000 (range 6000 to 32,000) individuals had been infected in Mexico by late April, giving an estimated case fatality ratio (CFR) of 0.4% (range: 0.3 to 1.8%) based on confirmed and suspected deaths reported to that time. In a community outbreak in the small community of La Gloria, Veracruz, no deaths were attributed to infection, giving an upper 95% bound on CFR of 0.6%. Thus, although substantial uncertainty remains, clinical severity appears less than that seen in the 1918 influenza pandemic but comparable with that seen in the 1957 pandemic. Clinical attack rates in children in La Gloria were twice that in adults (<15 years of age: 61%; ≥15 years: 29%). Three different epidemiological analyses gave basic reproduction number (R0) estimates in the range of 1.4 to 1.6, whereas a genetic analysis gave a central estimate of 1.2. This range of values is consistent with 14 to 73 generations of human-to-human transmission having occurred in Mexico to late April. Transmissibility is therefore substantially higher than that of seasonal flu, and comparable with lower estimates of R0 obtained from previous influenza pandemics.

Hantaviruses have the potential to cause two different types of diseases in human: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). HFRS, initially described clinically at the turn of the 20 th century, occurs endemically in the Asian and European continents, while HPS, recognized as a clinical entity since 1993, represents the prototype of emerging diseases occurring in the Western hemisphere. Approximately 150,000 to 200,000 cases of HFRS are hospitalized each year world wide, with most of the cases occurring in the developing countries. The case fatality rate of HFRS varies from <1% to 12% depending on the viruses. Although HPS is much smaller in number than HFRS, with approximately 200 HPS cases per year in the Americas, the average case fatality rate is 40%. The reported cases of hantaviral infection is increasing in many countries and new hantavirus strains have been increasingly identified worldwide, which constitutes a public health problem of increasing global concern. Hantaviral infection might be underestimated due to its asymptomatic and nonspecific mild infection, and the lack of simple standardized laboratory diagnostics in hospitals, especially in the developing countries. This review summarizes the current knowledge on virology, epidemiology, clinical manifestation, laboratory diagnostics, treatment and prevention of hantaviruses and hantaviral infections.

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Vasee Moorthy and colleagues describe the outcomes of a recent, WHO-led meeting on sharing research data and results during public health emergencies.