At that time, Paratyphi A was relatively common in North America (12).Today, Paratyphi A accounts for a sizable fraction (14–64%) of all enteric fever in India, Pakistan, Nepal, Indonesia, and China (13–16), but has largely disappeared from Europe and North America, except for travelers returning from South and Southeast Asia (17, 18).It is not possible to reconstruct what the disease burden of enteric fever was in the past because of insufficiently discriminatory historical descriptions of clinical syndromes.Until the mid-19th century, enteric fever was not even reliably distinguished from typhus (10), which is caused by , and the distinction between serovars Typhi and Paratyphi A was first achieved in 1898 (11).We also identified 273 mutations that were under Darwinian selection.
We performed short-read genomic sequencing (Illumina) of 142 Paratyphi A strains.
However, the time period over which humans have been afflicted by such diseases is only known for very few bacterial pathogens, and the evidence for recently increased virulence or fitness is scanty.
Has Darwinian (diversifying) selection at the genomic level recently driven microevolution within bacterial pathogens of humans?
Otherwise, little is known about its historical patterns of spread or its evolutionary history.
Phylogeographic reconstructions of genetically monomorphic pathogens can be achieved by comparative genomics (3, 4, 6, 19).
We used vertically acquired mutations identified by a novel algorithm to reconstruct the genealogy of Paratyphi A over the period of 450 y since its MRCA.