Abstract
In recent years, population and evolutionary biologists have questioned the traditional view that parasite-mediated morbidity and mortality¿virulence¿is a primitive character and an artifact of recent associations between parasites and their hosts. A number of hypotheses have been proposed that favor virulence and suggest that it will be maintained by natural selection. According to some of these hypotheses, the pathogenicity of HIV, Vibrio cholerae, Mycobacterium tuberculosis,theShigella,as well as Plasmodium falciparum,and many other microparasites, are not only maintained by natural selection, but their virulence increases or decreases as an evolutionary response to changes in environmental conditions or the density and/or behavior of the human population. Other hypotheses propose that the virulence of microparasites is not directly favored by natural selection; rather, microparasite-mediated morbidity and mortality are either coincidental to parasite-expressed characters (virulence determinants that evolved for other functions) or the product of short-sighted evolution in infected hosts. These hypotheses for the evolution and maintenance of microparasite virulence are critically reviewed, and suggestions are made for testing them experimentally.
Highlights
Rates To determine the expected demographics, rates of hospitalization, and international travel among patients with Salmonella Infantis infections compared with patients with infections caused by other common nontyphoidal Salmonella serotypes, we analyzed data collected through the Foodborne Disease Active Surveillance Network (FoodNet; https://www.cdc.gov/foodnet/index.html) during 2012–2015
The 2014 and 2015 St. Louis encephalitis virus (SLEV) isolates are genetically distinct from the 2003 Imperial Valley, California, strain that was isolated before the 11-year absence of SLEV activity in the state [49]. These results suggest there was likely a single introduction of SLEV into the United States from South America, and possibly Argentina, no later than November 2014, the earliest dated sample from which SLEV was isolated in Arizona and that the virus spread in the summer of 2015 from Arizona to California [49]
Investigation of Feeder Rats Owned by the Patient Because the patient kept feeder rats at home and these rats are a known source of Seoul virus (SEOV) infection, the rats were collected for source investigation
Summary
Rates To determine the expected demographics, rates of hospitalization, and international travel among patients with Salmonella Infantis infections compared with patients with infections caused by other common nontyphoidal Salmonella serotypes, we analyzed data collected through the Foodborne Disease Active Surveillance Network (FoodNet; https://www.cdc.gov/foodnet/index.html) during 2012–2015. Begun in 1996, FoodNet has conducted active, population-based surveillance for culture-confirmed cases of infection caused by 9 pathogens transmitted commonly through food, including Salmonella. The FoodNet surveillance area includes 15% of the US population; these data are used to estimate the burden of US foodborne illnesses, hospitalizations, and deaths [1]. L(+) tartrate+, Blockley, Anatum, Mississippi, and Panama. These 20 serotypes represented 69% of nontyphoidal Salmonella isolates reported to FoodNet in 2015
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
