Reanimated post

It seems appropriate to reanimate this blog post from the graveyard

I introduced the basic SIR model for a simple epidemic to you. This model actually has a long history and was first described by Kermack and McKendrick in 1927.

As I indicated this model has since been expanded to include virtually every disease scenario you can imagine.

In 2009 a group of Canadian mathematicians used this SIR format as the basis for an analysis of a zombie epidemic. Their paper: WHEN ZOMBIES ATTACK!: MATHEMATICAL MODELLING OF AN OUTBREAK OF ZOMBIE INFECTION ) - somehow it seemed appropriate to keep that in capitals) - describes a model that should look basically familiar to you.

Notice in their S Z R model (Z for Zombie of course) there are two extra transitions - from R back to Z (reanimation of the dead is well established in the zombie movie genre) and a movement directly from S to R (non zombie related death which can be quite high in this genre and so worth taking account of).

This is, perhaps unsurprisingly, the first mathematical analysis of an outbreak of zombie infection. While the scenarios considered are obviously not realistic, it is nevertheless instructive to develop mathematical models for an unusual outbreak. This demonstrates the flexibility of mathematical modelling and shows how modelling can respond to a wide variety of challenges in ‘biology’.

In summary, a zombie outbreak is likely to lead to the collapse of civilisation, unless it is dealt with quickly. While aggressive quarantine may contain the epidemic, or a cure may lead to coexistence of humans and zombies, the most effective way to contain the rise of the undead is to hit hard and hit often. As seen in the movies, it is imperative that zombies are dealt with quickly, or else we are all in a great deal of trouble.

Coming back to bite you

Would Bubonic Plague make a good weapon?

A 1970 World Health Organization assessment asserted that in a worst-case scenario a dissemination of 50 kg of Yersinia pestis in an aerosol cloud over a city of 5 million might result in 150,000 cases of pneumonic plague. Of those, 80,000 to 100,000 cases would require hospitalization, and 36,000 victims would be expected to die.

Of course there are numerous difficulties involved in getting 50kg of bacteria into an aerosol cloud. You could just breed infected fleas instead but, as the video says, they may well come back to bite you...

die.

Got Plague?

In 1914, three men in New Orleans examine rats to determine if they are carrying bubonic plague.  

This article from Discovery news this week has a slightly alarmist headline but makes some good points.

People in the US Still Die from Black Death

Plague, in humans, doesn't pop up a lot. Generally there are between one and seventeen cases per year in the United States, and only about a thousand in total since 1900. 

...

Remembering, and mentioning, exposure to dead or dying animals is key. As for efforts to eliminate it completely - although they've been considered, it would take too much extensive trapping and  it would take too much extensive trapping and testing of animals to be easily accomplished while the plague is still so rare. It looks like we'll continue getting the plague for the foreseeable future.

Traditional videos

The posting of the following videos has become traditional during the Bubonic Plague section of the course. The first one isn't strictly bubonic plague related, it's just included because of the flagellants.

The Daily Show with Jon Stewart	Mon - Thurs 11p / 10c
Bubonic Plague
www.thedailyshow.com
Daily Show Full Episodes Political Humor & Satire Blog The Daily Show on Facebook

Lizard loss

If lizards are so important in keeping California relatively Lyme disease free then what would happen if we were to lose the lizards from an area? This is the sort of thing that might happen with a dramatic change in habitat.

Well this has been tested experimentally and the results are a little surprising.

“Our expectation going into this study was that removing the lizards would increase the risk of Lyme disease, so we were surprised by these findings,” said study lead author Andrea Swei, who conducted the study while she was a Ph.D. student in integrative biology at UC Berkeley. “Our experiment found that the net result of lizard removal was a decrease in the density of infected ticks, and therefore decreased Lyme disease risk to humans.”
...

The researchers found that in plots where the lizards had been removed, ticks turned to the female woodrat as their next favorite host. On average, each female woodrat got an extra five ticks for company when the lizards disappeared.

However, the researchers found that 95 percent of the ticks that no longer had lizard blood to feast on failed to latch on to another host.

“One of the goals of our study is to tease apart the role these lizards play in Lyme disease ecology,” said Swei, who is now a post-doctoral associate at the Cary Institute of Ecosystem Studies in New York. “It was assumed that these lizards played an important role in reducing Lyme disease risk. Our study shows that it’s more complicated than that.”

Notwithstanding the results in this new study, Lane pointed out that the Western fence lizard are key to keeping infection rates down among adult ticks. “This study focused only on the risk from juvenile ticks, specifically those in the nymphal stage,” he said. “The earlier finding that adult ticks have lower infection rates because they feed predominantly on the Western fence lizard at the nymphal stage still holds.”

For more information check out this press release from UC Berkeley: Tick population plummets in absence of lizard hosts or the original article here: Impact of the experimental removal of lizards on Lyme disease risk.

Dengue Fever

 Five years ago I'd been using up some gift cards from amazon.com and had bought several items. Probably some music, but I don't remember what, and some books on disease including one on Yellow Fever. Some time later I got an e-mail highlighting items they thought I might like. I was amused to see they'd combined my viral hemorrhagic fever book with music to come up with the conclusion I'd like music by a band called Dengue Fever. The sort of stupid conclusion only a computer could reach. Except they were right.

In contrast to most bands with disease related names (eg Anthrax, Cholera, Bubonic Plague, Ebola etc etc) Dengue Fever are not only not a heavy metal band but play an impressive combination of almost everything else 'Southeast Asian pop, Vietnam-war-era lounge music, klezmer, ska, surf rock, and Ethiopian jazz'. One of the band apparently caught Dengue Fever which is where they got their name. I suspect Anthrax, Cholera, Bubonic Plague and Ebola can't say that. Dengue Fever (the band) are based in LA and so play in Santa Barbara quite frequently, usually at SoHo but next Friday (February 2nd) you can catch them right here on campus at the Multicultural Center.

If you want to know something about Dengue Fever, the disease, then read on.

Although it is the Filoviruses such as Ebola that leap to mind when people hear the phrase 'viral hemorrhagic fever' (VHF) there are actually four different families of viruses that can lead to the classic symptoms of VHF's - capilliary leak leading to high temperature, shock (loss of blood pressure) and death.

This is rather important because whilst the Ebolavirus is really very rare some of the other VHF's are far more common. We'll talk about Yellow Fever in the penultimate week but another disease in the same group is Dengue Fever. Although 50-100 million people are estimated to contract this mosquito borne disease every year only a minority get a severe hemorrhagic fever. Maybe 5%. But 5% of 50-100 million is still several million people per year! In the severe form Dengue Fever causes a very high fever (over 104) and generalized muscle and joint pain (hence the common name 'breakbone fever').

It is the most common viral disease transmitted by arthropods and it is deemed second in importance to malaria in terms of tropical diseases. The World Health Organization currently counts dengue as one of sixteen neglected tropical diseases and it is found in a wide range of tropical countries across South America, Africa and Asia.

A tale of two Romneys

You can read more about America's rioting cities of the 1960's at PBS's American Experience website for 'Eyes on the Prize - America's civil right's movement 1954-1985'.

For five days in July, Detroit, Michigan descends into chaos. An economic boom has created jobs, and urban renewal projects have built new infrastructure, but blacks have been left behind. New expressways destroy black neighborhoods, and economic opportunities are scarce for black residents. The 95% white police force, notorious for brutal and arbitrary treatment of black citizens, raids an illegal after hours club and draws an angry, frustrated crowd that quickly turns hostile.

As Sunday July 23rd dawns, the growing crowd is looting and burning the city. Twelve hours into the frenzy, Governor George Romney calls in the Michigan National Guard; unprepared troops make mistakes like shooting out the street lights. Nearly 4000 people will be arrested in the first two days, and over 7000 by the third. Most are young and black. Police and guardsmen shoot at will, with some later insisting that all of their victims were armed.

Romney asks President Lyndon Johnson for federal help and by Monday afternoon 4700 U.S. Army paratroopers have arrived, under orders not to use live ammunition. A combined 17,000 law enforcement troops suppress the riot. After five days of anarchy, more than 40 people are dead, hundreds are injured, and damage estimates hit $50 million.

Yup, this is Governor George Romney, father of Mitt, and a leading Republican contender to challenge Lyndon Johnson for the presidency the following year. Romney believed the White House had intentionally slowed its response to the riots and he accused Johnson with having "played politics" in his actions. George Romney went on to lose to Richard Nixon in the Republican primary after running a poor campaign.

"Watching George Romney run for the presidency was like watching a duck try to make love to a football." Governor Jim Rhodes of Ohio

Over four decades later and it's Mitt's turn. Over those four decades the exodus from America's cities to the suburbs has played an unknown role in the rise of Lyme disease. A new political tool that has arisen is 'micro-targeting' allowing you to target each voter with the issues that are important to them.

The Romney-Ryan campaign 2012 goes with Lyme Disease in Virginia. The front of their mailer contains the rather general Romney-Ryan. Doing more to fight the spread of Lyme disease. Improve synergy. Increase awareness. Support treatment.

But the back explains just what this means.

It almost sounds reasonable until you ask yourself why a doctor would need protection from lawsuits...

Soundtrack for this post: Motor City is Burning by the MC5