US control strategies may make flu epidemics worse, study shows

Regular as clockwork, the flu arrives every year. And, according to the national Centers for Disease Control and Prevention, 5 to 20 percent of the U.S. population on average will come down with it. About 36,000 people will die.

But among health experts, a bigger concern than the seasonal flu is an outright flu pandemic, such as a human strain of avian flu. And officials say it is not a question of if such a health crisis will come but when. Are we prepared? In a word, say three UCLA researchers, no.

In a report to be published in the peer-reviewed journal PLoS Computational Biology and currently available online, Sally Blower, a professor at the Semel Institute for Neuroscience and Human Behavior at UCLA, and Romulus Breban and Raffaele Vardavas, postdoctoral fellows in Blower's research group, used novel mathematical modeling techniques to predict that current health policy — based on voluntary vaccinations — is not adequate to control severe flu epidemics and pandemics unless vaccination programs offer incentives to individuals.

According to the researchers, the severity of such a health crisis could be reduced if programs were to provide several years of free vaccinations to individuals who pay for only one year. Interestingly, however, some incentive programs could have the opposite effect. Providing free vaccinations for entire families, for example, could actually increase the frequency of severe epidemics. This is because when the head of the household makes a choice — flu shots or no flu shots — on behalf of all the other household members, there is no individual decision-making, and adaptability is decreased.

While other models have determined what proportion of the population would need to be vaccinated in order to prevent a pandemic, none of these models have shown whether this critical coverage can actually be reached. What has been missing, according to Blower, a mathematical and evolutionary biologist, is the human factor.

The human factor involves two biological characteristics, "memory and how adaptable people can be," Blower said. "These characteristics drive human behavior."

Blower and her group used people's attitudes toward the seasonal flu to construct their model. With seasonal flu, protective immunity — a flu shot — lasts only one year. Thus, individuals must decide each year whether or not to participate in a vaccination program.

The model Blower's team developed is inspired by game theory, used in economics to predict how non-communicating, selfish individuals reach a collective behavior with respect to a common dilemma by adapting to what they think are other people's decisions. The group modeled each individual's strategy for making yearly vaccination decisions as an adaptive process of trial and error. They tracked both individual-level decisions and population-level variables — that is, the yearly vaccine coverage level and influenza prevalence, where prevalence is defined as the proportion of the population that is infected. The individual-level model was based on the human biological attributes of memory and adaptability.

"We assume that the decision of each individual is based upon self-interest, that people wish to avoid coming down with the flu, preferably without having to vaccinate," said Breban.

It is the adaptive decision-making by the individual, the researchers say, that may be an important and previously overlooked causal factor in driving influenza epidemiology.

"Including cognitive and personality factors into epidemic models can dramatically change our understanding of why flu epidemics occur." said Vardavas.

Source: Public Library of Science

Related stories:

Govt pays for deadly, unapproved drugs (Update)
(AP) -- Dozens of deaths have been linked to medications that have never been reviewed by the government for safety and effectiveness but are still covered under Medicaid, an Associated Press analysis of federal data has found.
Thailand confirms second bird flu case
Thailand has confirmed a second case of bird flu in less than a week, a senior agriculture official said Thursday.
Thailand confirms fresh bird flu outbreak
Thailand's agriculture ministry said Monday that it had confirmed an outbreak of bird flu on a backyard farm in the north, six months after the kingdom was declared free of the deadly virus.
Masks, hand washing, prevent spread of flu-like symptoms by up to 50 percent
Wearing masks and using alcohol-based hand sanitizers may prevent the spread of flu symptoms by as much as 50 percent, a landmark new study suggests.
Avian flu threat: New approach needed
As the first globally co-ordinated plan for the planet's gravest health threats is hatched by government ministers from around the world this weekend, a new report sets out a 10-point plan for this new, globalised approach to infectious diseases such as avian flu.
Researchers develop cross-protective vaccine
(PhysOrg.com) -- Doctors have always hoped that scientists might one day create a vaccination that would treat a broad spectrum of maladies. They could only imagine that there might be one vaccine that would protect against, say, 2,500 strains of Salmonella. And what if that same vaccine could help protect the elderly?
'Deadly dozen' reports diseases worsened by climate change
Health experts from the Wildlife Conservation Society today released a report that lists 12 pathogens that could spread into new regions as a result of climate change, with potential impacts to both human and wildlife health and global economies. Called The Deadly Dozen: Wildlife Diseases in the Age of Climate Change, the new report provides examples of diseases that could spread as a result of changes in temperatures and precipitation levels. The best defense, according to the report's authors, is a good offense in the form of wildlife monitoring to detect how these diseases are moving so health professionals can learn and prepare to mitigate their impact.
Existing anti-obesity drugs may be effective against flu, hepatitis and HIV
Viruses dramatically increase cellular metabolism, and existing anti-obesity drugs may represent a new way to block these metabolic changes and inhibit viral infection, according to a study published today in the journal Nature Biotechnology.

News discussion:

Medicine & Health news