RESEARCH REPORT: Role of ‘friendship paradox’ possible in epidemics

Lynne Friedmann is a science writer based in Solana Beach. Her regular column features local science news.

By Lynne Friedmann

A “friendship paradox” may help predict the spread of infectious disease. First described in 1991, the paradox states that, statistically, the friends of any given individual are likely more popular than the individual herself. Thus, in a random group, ask each person to name one friend, and on average the named friends will rank higher in that social network.

Researchers at Harvard University and UCSD applied this observation to a study during the 2009 flu epidemic. As flu season approached, 319 Harvard undergraduates were contacted who, in turn, named a total of 425 friends. Monitoring the two groups — through self-reporting and Harvard University Health Services data — the researchers found that the “friends” contracted the flu roughly two weeks prior to the random group and a full 46 days prior to the epidemic peak.

Currently there’s a lag time in tracking epidemics because people aren’t monitored until they become ill. A means to monitor social networks and predict an epidemic before it strikes the general population would allow for an earlier, more vigorous, and more effective response by public health officials.

The study appears the online, open-access journal PLoS ONE. News release at

Infectious origin of obesity
Among risk factors for childhood obesity are poor eating habits, lack of exercise, family history, ethnicity, stress or depression, as well as socioeconomic status. Add to this the idea that obesity may have an infectious origin.

That emerging idea has new support following a study by UCSD School of Medicine researchers who found that children exposed to a particular strain of adenovirus were more likely to be obese.

Researchers examined 124 children. Slightly more than half of the children in the study (67) were considered obese, based on an elevated Body Mass Index. All of the children were tested for the presence of antibodies specific to adenovirus 36 (AD36); the only human adenovirus currently linked to human obesity. Antibodies were detected in 19 of the children (15 percent) in the study, and the majority of AD36-positive children (78 percent) were obese.

The study appears in the journal Pediatrics. News release

Modeling immune system
Scientists from the UCSD School of Medicine have identified dendritic cells (DCs) in zebrafish. Heretofore, it was not clear whether these cells existed in non-mammalian vertebrates. The discovery means that the tiny fish could one day serve as a model for studying the complexities of the human immune system.

In mammals, DCs are a crucial link between the innate immune system (short-lived, non-specific defense against infection) and adaptive immune systems (more complex and long-lasting protection against specific pathogens).

The discovery of DCs in zebrafish provides researchers with another model for investigating the mammalian immune system, particular with regard to humans. And, because the fish are translucent, researchers can track individual cells and systems directly, in real time, in the whole animal.

The finding is reported in the Proceedings of the National Academy of Science. News release at

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Posted by Halie Johnson on Sep 23, 2010. Filed under Columns, Health & Science, News, Research Report. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

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