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Evidence for several waves of global transmission in the seventh cholera pandemic
Mutreja, Ankur,Kim, Dong Wook,Thomson, Nicholas R.,Connor, Thomas R.,Lee, Je Hee,Kariuki, Samuel,Croucher, Nicholas J.,Choi, Seon Young,Harris, Simon R.,Lebens, Michael,Niyogi, Swapan Kumar,Kim, Eun J Nature Publishing Group, a division of Macmillan P 2011 Nature Vol.477 No.7365
Vibrio cholerae is a globally important pathogen that is endemic in many areas of the world and causes 3??5??million reported cases of cholera every year. Historically, there have been seven acknowledged cholera pandemics; recent outbreaks in Zimbabwe and Haiti are included in the seventh and ongoing pandemic. Only isolates in serogroup O1 (consisting of two biotypes known as ??classical?? and ??El Tor??) and the derivative O139 (refs 2, 3) can cause epidemic cholera. It is believed that the first six cholera pandemics were caused by the classical biotype, but El Tor has subsequently spread globally and replaced the classical biotype in the current pandemic. Detailed molecular epidemiological mapping of cholera has been compromised by a reliance on sub-genomic regions such as mobile elements to infer relationships, making El Tor isolates associated with the seventh pandemic seem superficially diverse. To understand the underlying phylogeny of the lineage responsible for the current pandemic, we identified high-resolution markers (single nucleotide polymorphisms; SNPs) in 154 whole-genome sequences of globally and temporally representative V.??cholerae isolates. Using this phylogeny, we show here that the seventh pandemic has spread from the Bay of Bengal in at least three independent but overlapping waves with a common ancestor in the 1950s, and identify several transcontinental transmission events. Additionally, we show how the acquisition of the SXT family of antibiotic resistance elements has shaped pandemic spread, and show that this family was first acquired at least ten years before its discovery in V.??cholerae.
Uncovering an anthropogenic sea-level rise signal in the Pacific Ocean
Hamlington, B. D.,Strassburg, M. W.,Leben, R. R.,Han, W.,Nerem, R. S.,Kim, K-Y. Nature Publishing Group, a division of Macmillan P 2014 Nature climate change Vol.4 No.9
Internal climate variability across a range of scales is known to contribute to regional sea-level trends, which can be much larger than the global mean sea-level trend in many parts of the globe. Over decadal timescales, this internal variability obscures the long-term sea-level change, making it difficult to assess the effect of anthropogenic warming on sea level. Here, an attempt is made to uncover the sea-level rise pattern in the tropical Pacific Ocean associated with anthropogenic warming. More specifically, the sea-level variability associated with the Pacific Decadal Oscillation is estimated and removed from the regional sea-level trends computed from satellite altimetry measurements over the past two decades. The resulting pattern of regional sea-level rise uncovered in the tropical Pacific Ocean is explained in part by warming in the tropical Indian Ocean, which has been attributed to anthropogenic warming. This study represents one of the first attempts at linking the sea-level trend pattern observed by satellite altimetry to anthropogenic forcing.