Unvaccinated infants act as 'kindling' to fuel epidemics

April 1, 2014, University of Michigan

Nearly 4 million children under 5 die from vaccine-preventable diseases worldwide each year, and two University of Michigan doctoral ecology students are working to change that.

By taking into account seasonal fluctuations in birth rates, massive vaccination campaigns in the developing world could inoculate more unprotected infants and significantly reduce the number of deaths from diseases like measles, according to Micaela Martinez-Bakker and Kevin Bakker of the U-M Department of Ecology and Evolutionary Biology.

"If you have lots of kindling, you can have a bigger fire, and that's essentially the role that these susceptible infants play during measles outbreaks. If lots of new births flood into the population before a measles epidemic peaks, they can add fuel to the flames and make that year's epidemic bigger," said Martinez-Bakker, an NSF Doctoral Fellow whose work is supported by the U.S. National Science Foundation.

"There are predictable times of year when we know there are going to be more infants being born, and we hope that in the future this information will be used to help control epidemics," she said.

The husband-and-wife research team studies how birth seasonality—the variation in the timing and strength of birth pulses throughout the year—can shape outbreaks of childhood infectious diseases.

Wildlife disease ecologists have known for years that the timing of birth pulses helps shape epidemics of various animal diseases, and the U-M researchers wanted to know if the same is true for humans.

They digitized 78 years of monthly birth records from every U.S. state and obtained more than 200 data sets from countries across the Northern Hemisphere, then fed the information into a disease transmission model for measles to examine the implications of birth seasonality on childhood infections.

They found that the timing and magnitude of seasonal birth pulses could significantly alter the size of a measles epidemic.

A paper detailing their findings is scheduled for online publication April 1 in the journal Proceedings of the Royal Society B. Department of Ecology and Evolutionary Biology faculty researchers Pejman Rohani and Aaron King are co-authors.

Measles is a childhood disease that is often spread at schools, where youngsters congregate and swap germs. Martinez-Bakker and Bakker show that years before they enter school, unvaccinated infants also play a significant role in disease transmission and can worsen a measles epidemic.

Public health officials could use these birth seasonality insights to optimize mass vaccination campaigns, such as the and polio efforts the World Health Organization conducts in Africa, the eastern Mediterranean and Southeast Asia. The timing of those once-a-year efforts could be adjusted to assure that they include infants recently added to the population, according to Martinez-Bakker and Bakker.

Demographers have known since the early 1800s that the number of human births varies from season to season. In the United States, early studies of vital statistics in various U.S. regions established a national-level seasonal pattern of births with troughs in the spring and peaks in autumn. Over the decades, various factors have been advanced to explain these patterns—income, culture, race, holidays, rainfall, cold winters and even the seasonally variable quality of sperm—but no single driver of birth seasonality has been identified.

Bakker recently gained access to long-term birth records from more than 70 African and Southeast Asian countries. As part of his dissertation, he will determine the relative roles of birth rate, the timing of birth peaks, and the magnitude of those peaks in epidemics of childhood infections.

Those signals should be fairly easy to spot in African data, he said, because and the strength of seasonal birth pulses are high there, and endemic childhood diseases are common.

As part of the study reported in the Proceedings of the Royal Society B, Martinez-Bakker and Bakker also uncovered patterns in U.S. birth seasonality that previous, much more limited investigations had identified without exploring in depth.

In the United States, the U-M researchers found that the timing of annual birth pulses varied with latitude, with northern states exhibiting a spring-summer peak and southern states showing an autumn peak.

They compiled a Northern Hemisphere data set that includes information about 730 million births. They describe their demographic data set as "the most extensive spatiotemporal data set on human births to date."

Explore further: Preterm infants more likely to have elevated insulin levels in early childhood

More information: Human Birth Seasonality: Latitudinal Gradient and Interplay with Childhood Disease Dynamics, rspb.royalsocietypublishing.or … .1098/rspb.2013.2438

Related Stories

Preterm infants more likely to have elevated insulin levels in early childhood

February 11, 2014
Researchers have found that preterm infants are more likely to have elevated insulin levels at birth and in early childhood compared to full-term infants, findings that provide additional evidence that preterm birth may be ...

Researchers reveal hidden patterns that help explain stubborn persistence of measles

August 23, 2013
Despite the availability of a cheap and effective vaccine, measles remains a leading cause of childhood mortality worldwide, killing more than 150,000 individuals in 2011. In a new study, researchers at the University of ...

Some racial disparities in childbirth more environmental than genetic

March 13, 2014
A new study investigating racial disparities in birth outcomes shows that contrary to some theories Vitamin D is unlikely to play a role in differences in preterm birth and low birth weight between African-Americans and whites.

Study shows link between high birth weight and heart disease

March 25, 2014
(Medical Xpress)—Babies born with high birth weight may be at increased risk of cardiovascular disease in adulthood, according to a University of Sydney study.

Measles deaths fall to record low, but rebound in Syria

February 6, 2014
The number of people dying from measles has fallen to a record low, driven down by mass vaccination campaigns, but outbreaks in crisis zones such as Syria remain a threat, the UN said Thursday.

Researchers suggest China consider national flu vaccination plan with staggered timing

November 19, 2013
China should tailor its influenza vaccination strategies to account for its three distinct flu regions, according to the first comprehensive study of the country's flu patterns conducted by a research team of Chinese and ...

Recommended for you

Sleep better, lose weight?

January 17, 2018
(HealthDay)—Sleeplessness could cost you when it's time to stand on your bathroom scale, a new British study suggests.

Who uses phone apps to track sleep habits? Mostly the healthy and wealthy in US

January 16, 2018
The profile of most Americans who use popular mobile phone apps that track sleep habits is that they are relatively affluent, claim to eat well, and say they are in good health, even if some of them tend to smoke.

Improvements in mortality rates are slowed by rise in obesity in the United States

January 15, 2018
With countless medical advances and efforts to curb smoking, one might expect that life expectancy in the United States would improve. Yet according to recent studies, there's been a reduction in the rate of improvement in ...

Teens likely to crave junk food after watching TV ads

January 15, 2018
Teenagers who watch more than three hours of commercial TV a day are more likely to eat hundreds of extra junk food snacks, according to a report by Cancer Research UK.

Can muesli help against arthritis?

January 15, 2018
It is well known that healthy eating increases a general sense of wellbeing. Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have now discovered that a fibre-rich diet can have a positive influence ...

Your dishwasher is not as sterile as you think

January 13, 2018
(HealthDay)—Your dishwasher may get those plates spotless, but it is also probably teeming with bacteria and fungus, a new study suggests.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.