Studying Possible Pandemic Through Three Plagues Linked To Same Bacterial Pathogen

Mapping the spread of a pandemic

Scientists discovered that the two most devastating plagues, the plague of Justinian and the Black Death, responsible for killing 50% of Europe, were caused by distinct strains of the Yersinia pestis bacteria.

There have been three major plague outbreaks; The Plague of Justinian in the 6th and 7th centuries, The Black Death in the 12th century and in the 1890s, another outbreak of the Black Death appeared in China and India.

Prior to the study, there is little information on the cause or origin of the Justinian plague. They reconstructed the genome by isolating DNA fragments of 1500 year old teeth of two victims of the Justinan plague and noted that it was caused by a strain of the Yersinia pestis bacteria.

The first two plagues appeared 800 years apart and scientists are wondering how the two plagues were linked and how one can just fade (Justinian plague) and the other can re-emerge 700 years later.

Their study suggests that a new strain of the plague can emerge again in the future.

Studying Current 21st Century Patterns of a Spreading Pandemic

World map shows flight routes from the 40 largest U.S. airports.
Image: Christos Nicolaides, Juanes Research Group

Northwestern University developed a computational model, based on transportation data, that determines its source and how quickly a pandemic will spread to a specific location.

A pandemic refers to an epidemic of infectious disease that has spread across a large area or even in global proportions. It occurs when a strain of a virus appears that causes a readily transmissible disease for which most have no immunity. Influenza pandemics are the most common and occurs with little or no warning and infects a large area of population in multiple waves.

In 1918, The Spanish Flu Pandemic infected 500 million worldwide and killed 20 to 30 million. At the time, the death toll equates to about one to three percent of the world's population, making it one of the deadliest natural disasters in human history. The most recent pandemic was the 2009 H1N1 flu pandemic that killed about 300,000 people worldwide.

Recently, scientists are worried about the H5N1 virus, also known as the avian flu virus. Currently it only affects birds but studies have surfaced showing how this virus can be modified to infect mammals. They believe that if this virus carries over to humans, it may cause a pandemic that will overshadow the disaster brought about by the Spanish Flu Pandemic.

Scientists are studying how pandemics can spread worldwide and how this can be contained in the fastest and most effective way. With the advent of air travel and how fast one can travel from one point in the world to another, the dynamics of a spreading disease has changed from how it was centuries ago.

AAAS News: Letter on Resuming Avian Flu Transmission Research

At the start of 2012, the US National Science Advisory Board for Biosecurity recommended restricting the publication of results from research on H5N1 avian influenza virus. This was with regards to previous developments on the H5N1 virus leading to a discovery for the generation of the virus to be made transmissible to mammals.

The experiment involved ferrets who acquired the virus, previously almost exclusive only to birds, through respiratory droplets. There was concern that this discovery may lead to the virus affecting humans.

Based on rare cases of humans contracting H5N1, there is a 59% chance of mortality once the disease is contracted. To put this into perspective, the Spanish Flu in 1918 that killed an estimated 50 to 100 million people the world over, only had a mortality rate of just 2%.

The National Science Advisory Board for Biosecurity is a panel of the United States Department of Health and Human Services. It was decided by the panel that the research behind H5N1 poses a significant health and security threat. They recommended restricting the publication of results from research on H5N1 avian influenza virus, leading to the generation of viruses that are more transmissible in mammals.

In January 2012, influenza researchers from around the world announced a voluntary pause on any research involving H5N1 influenza viruses which may lead to it being more transmissible in mammals.

H5N1 Controversy One Year Later

Correspondence signed by 40 influenza virus researchers and jointly published in Science and Nature this week announces that the voluntary pause on certain types of H5N1 avian influenza research should end in countries where the aims of this moratorium have been met and authorities have reached decisions about how best to conduct such work safely.

MIT News: Airports Major Influence In Spreading Disease and Cause A Pandemic

World map shows flight routes from the 40 largest U.S. airports.
Image: Christos Nicolaides, Juanes Research Group

Public health crises of the past decade — such as the 2003 SARS outbreak, which spread to 37 countries and caused about 1,000 deaths, and the 2009 H1N1 flu pandemic that killed about 300,000 people worldwide — have heightened awareness that new viruses or bacteria could spread quickly across the globe, aided by air travel.

While epidemiologists and scientists who study complex network systems — such as contagion patterns and information spread in social networks — are working to create mathematical models that describe the worldwide spread of disease, to date these models have focused on the final stages of epidemics, examining the locations that ultimately develop the highest infection rates.

But a new study by researchers in MIT’s Department of Civil and Environmental Engineering (CEE) shifts the focus to the first few days of an epidemic, determining how likely the 40 largest U.S. airports are to influence the spread of a contagious disease originating in their home cities. This new approach could help determine appropriate measures for containing infection in specific geographic areas and aid public health officials in making decisions about the distribution of vaccinations or treatments in the earliest days of contagion.

Unlike existing models, the new MIT model incorporates variations in travel patterns among individuals, the geographic locations of airports, the disparity in interactions among airports, and waiting times at individual airports to create a tool that could be used to predict where and how fast a disease might spread.