Limits...
The role of China in the global spread of the current cholera pandemic.

Didelot X, Pang B, Zhou Z, McCann A, Ni P, Li D, Achtman M, Kan B - PLoS Genet. (2015)

Bottom Line: We sequenced the genomes of 71 strains isolated in China between 1961 and 2010, as well as eight from other sources, and compared them with 181 published genomes.The results indicated that outbreaks in China between 1960 and 1990 were associated with wave 1 whereas later outbreaks were associated with wave 2.We therefore suggest replacing them by a series of tightly delineated clades.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom.

ABSTRACT
Epidemics and pandemics of cholera, a severe diarrheal disease, have occurred since the early 19th century and waves of epidemic disease continue today. Cholera epidemics are caused by individual, genetically monomorphic lineages of Vibrio cholerae: the ongoing seventh pandemic, which has spread globally since 1961, is associated with lineage L2 of biotype El Tor. Previous genomic studies of the epidemiology of the seventh pandemic identified three successive sub-lineages within L2, designated waves 1 to 3, which spread globally from the Bay of Bengal on multiple occasions. However, these studies did not include samples from China, which also experienced multiple epidemics of cholera in recent decades. We sequenced the genomes of 71 strains isolated in China between 1961 and 2010, as well as eight from other sources, and compared them with 181 published genomes. The results indicated that outbreaks in China between 1960 and 1990 were associated with wave 1 whereas later outbreaks were associated with wave 2. However, the previously defined waves overlapped temporally, and are an inadequate representation of the shape of the global genealogy. We therefore suggest replacing them by a series of tightly delineated clades. Between 1960 and 1990 multiple such clades were imported into China, underwent further microevolution there and then spread to other countries. China was thus both a sink and source during the pandemic spread of V. cholerae, and needs to be included in reconstructions of the global patterns of spread of cholera.

Show MeSH

Related in: MedlinePlus

Circular plot illustrating the inferred migrations between geographical locations.Flow bars indicate the sources of transmissions, colored as in Fig. 3, with one end of the bar directly touching the country of origin, and the other end of the bar having a small gap before the country of destination. The average date for each migration is shown on the ends corresponding to the origin.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4358972&req=5

pgen.1005072.g004: Circular plot illustrating the inferred migrations between geographical locations.Flow bars indicate the sources of transmissions, colored as in Fig. 3, with one end of the bar directly touching the country of origin, and the other end of the bar having a small gap before the country of destination. The average date for each migration is shown on the ends corresponding to the origin.

Mentions: In order to investigate these source/sink relationships in greater detail we inferred the ancestral geographical locations of branches by a maximum parsimony reconstruction of states, summarizing sources and sinks for international transmissions by a circular plot [30,31] (S4 Table; Fig. 4). Our data indicate nine transmissions out of South Asia, including twice into Africa in the 1990s, twice into Pakistan between 2002 and 2005, and once into Nepal around 2005. The strain causing the Haitian 2010 outbreak was confirmed to have originated in Nepal, as previously suggested [9]. Likewise, we also confirmed pandemic spread from Africa into South America in the 1980s [6]. These conclusions should be considered as minimal estimates of the numbers of transmissions because numerous sources of international outbreaks and endemic disease have not been investigated, leading to sampling bias. In contrast, more genomes have now been sequenced from China than from any other single source, and the Chinese strains are representative of disease over the entire period from 1961 until 2005. Our analysis of global transmissions (Fig. 4) indicates that China imported V. cholerae four times from South Asia (1975–2004), once from Indonesia (1955) and once from Southeast Asia (1986). In turn, China was the source of transmissions to South Asia (three times, 1967–1999), Indonesia (1960) and Southeast Asia (2007). These results suggest that V. cholerae populations are often transmitted between East Asia, South Asia and Southeast Asia, which makes it difficult to pinpoint the exact origins or outbreaks in other parts of the world. Even if China is not the direct origin for such outbreaks, it clearly represents an important reservoir of diversity which needs to be accounted for when modeling the global epidemiology of cholera.


The role of China in the global spread of the current cholera pandemic.

Didelot X, Pang B, Zhou Z, McCann A, Ni P, Li D, Achtman M, Kan B - PLoS Genet. (2015)

Circular plot illustrating the inferred migrations between geographical locations.Flow bars indicate the sources of transmissions, colored as in Fig. 3, with one end of the bar directly touching the country of origin, and the other end of the bar having a small gap before the country of destination. The average date for each migration is shown on the ends corresponding to the origin.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4358972&req=5

pgen.1005072.g004: Circular plot illustrating the inferred migrations between geographical locations.Flow bars indicate the sources of transmissions, colored as in Fig. 3, with one end of the bar directly touching the country of origin, and the other end of the bar having a small gap before the country of destination. The average date for each migration is shown on the ends corresponding to the origin.
Mentions: In order to investigate these source/sink relationships in greater detail we inferred the ancestral geographical locations of branches by a maximum parsimony reconstruction of states, summarizing sources and sinks for international transmissions by a circular plot [30,31] (S4 Table; Fig. 4). Our data indicate nine transmissions out of South Asia, including twice into Africa in the 1990s, twice into Pakistan between 2002 and 2005, and once into Nepal around 2005. The strain causing the Haitian 2010 outbreak was confirmed to have originated in Nepal, as previously suggested [9]. Likewise, we also confirmed pandemic spread from Africa into South America in the 1980s [6]. These conclusions should be considered as minimal estimates of the numbers of transmissions because numerous sources of international outbreaks and endemic disease have not been investigated, leading to sampling bias. In contrast, more genomes have now been sequenced from China than from any other single source, and the Chinese strains are representative of disease over the entire period from 1961 until 2005. Our analysis of global transmissions (Fig. 4) indicates that China imported V. cholerae four times from South Asia (1975–2004), once from Indonesia (1955) and once from Southeast Asia (1986). In turn, China was the source of transmissions to South Asia (three times, 1967–1999), Indonesia (1960) and Southeast Asia (2007). These results suggest that V. cholerae populations are often transmitted between East Asia, South Asia and Southeast Asia, which makes it difficult to pinpoint the exact origins or outbreaks in other parts of the world. Even if China is not the direct origin for such outbreaks, it clearly represents an important reservoir of diversity which needs to be accounted for when modeling the global epidemiology of cholera.

Bottom Line: We sequenced the genomes of 71 strains isolated in China between 1961 and 2010, as well as eight from other sources, and compared them with 181 published genomes.The results indicated that outbreaks in China between 1960 and 1990 were associated with wave 1 whereas later outbreaks were associated with wave 2.We therefore suggest replacing them by a series of tightly delineated clades.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom.

ABSTRACT
Epidemics and pandemics of cholera, a severe diarrheal disease, have occurred since the early 19th century and waves of epidemic disease continue today. Cholera epidemics are caused by individual, genetically monomorphic lineages of Vibrio cholerae: the ongoing seventh pandemic, which has spread globally since 1961, is associated with lineage L2 of biotype El Tor. Previous genomic studies of the epidemiology of the seventh pandemic identified three successive sub-lineages within L2, designated waves 1 to 3, which spread globally from the Bay of Bengal on multiple occasions. However, these studies did not include samples from China, which also experienced multiple epidemics of cholera in recent decades. We sequenced the genomes of 71 strains isolated in China between 1961 and 2010, as well as eight from other sources, and compared them with 181 published genomes. The results indicated that outbreaks in China between 1960 and 1990 were associated with wave 1 whereas later outbreaks were associated with wave 2. However, the previously defined waves overlapped temporally, and are an inadequate representation of the shape of the global genealogy. We therefore suggest replacing them by a series of tightly delineated clades. Between 1960 and 1990 multiple such clades were imported into China, underwent further microevolution there and then spread to other countries. China was thus both a sink and source during the pandemic spread of V. cholerae, and needs to be included in reconstructions of the global patterns of spread of cholera.

Show MeSH
Related in: MedlinePlus