Rotavirus is a leading cause of diarrhea among children, both in the developed and developing world. In the United States, the virus causes about 60,000 hospitalizations each year and kills about 40 children below the age of five.
"It is an imperfectly immunizing infection," said Virginia Pitzer, postdoctoral researcher in the Center for Infectious Disease Dynamics and the department of biology, Penn State. "So you can get infected multiple times throughout your life."
Up until the late 1990s, annual rotavirus epidemics in the U.S. followed a predictable pattern. Infections appeared in the southwest and peaked in December or January, then spread to the northeast, where they peaked in March. In recent years epidemics in the southwest have begun later than usual.
Pitzer and her colleagues initially looked at environmental factors such as solar radiation, precipitation and temperature but these could not explain the shifts in outbreaks of new infections. Unlike other viruses that die out and are replenished each year with new strains from outside the United States, rotavirus infections tend to linger in the summer months.
"In general, the pattern of spread of rotavirus outbreaks from the southwest to the northeast is not consistent with any climatic factors," explained Pitzer, whose findings appear today (July 17) in Science. "For instance, temperature tends to be high in the southwest but it also tends to be high in places like Florida, where epidemics occur much later."
Instead, Pitzer and her colleagues looked at human birth rates and the potential link to the timing of rotavirus epidemics. While birth rates are typically high in the southwest and low in the northeast, census data indicates a recent decline in the southwest, particularly in California.
Statistical analysis suggested a negative correlation between birth rates and the timing of the epidemics between 1991 and 2006.
"Each time there was a decline in birth rate, whether from state to state or year to year, infections tended to happen later," explained Pitzer.
A mathematical model using information on the epidemiology of rotavirus and birth rates from states confirmed the statistical correlation and predicted that given the declining birth rate in California, rotavirus epidemics in the state would gradually shift from December to February.
"Since infants often have diarrhea and can be very infectious when they get rotavirus, they are the ones who tend to drive the epidemics," said Pitzer, who is also associated with Fogarty International Center at the National Institutes of Health through the Research and Policy for Infectious Disease Dynamics program. "Thus, you can get outbreaks of rotavirus happening a lot sooner when and where there are more infants being born."
Vaccines introduced in 2006 further confirm Pitzer's model. Since vaccination reduces the number of infants vulnerable to symptomatic infections, the effect is analogous to a decline in birth rate.
"With the effects of vaccination factored in, the model accurately predicted a small decrease in the incidence of severe diarrhea during the 2006-2007 season, and a larger decline and delay during 2007-2008, providing validation for our model," said Pitzer.
Researchers add that high levels of vaccination could further limit the intensity of new epidemics and lead to a period of years with very few cases of severe diarrhea caused by rotavirus.
"The important message here is that vaccination can have a big impact in controlling rotavirus infections," explained Pitzer. "Even those not vaccinated can benefit from those vaccinated because it lowers the overall prevalence of the infection in the population."
Other researchers on the paper include Cecile Viboud, staff scientist; Wladimir J. Alonso, research fellow, and Mark A. Miller, director, division of international epidemiology, all at the Fogarty International Center, National Institutes of Health; Lone Simonsen, visiting professor, George Washington University; Claudia Steiner, research medical officer, U.S. Department of Health and Human Services; Umesh D. Parashar, lead, viral gastroenteritis epidemiology team; Catherine A. Panozzo, surveillance coordinator; and John W. Glasser, epidemiologist, all at the National Center for Immunization and Respiratory Diseases, U.S. Centers for Disease Control and Prevention; and Bryan T. Grenfell, professor, Princeton University, formerly at Penn State.
The National Institutes of Health, Bill and Melinda Gates Foundation, and the U.S. Department of Homeland Security supported this work.
Amitabh Avasthi | EurekAlert!
Meadows beat out shrubs when it comes to storing carbon
23.11.2017 | Norwegian University of Science and Technology
Migrating Cells: Folds in the cell membrane supply material for necessary blebs
23.11.2017 | Westfälische Wilhelms-Universität Münster
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
23.11.2017 | Information Technology
23.11.2017 | Physics and Astronomy
23.11.2017 | Life Sciences