Jonas Salk’s 100th Birthday

October 26, 2014 · Posted in Medicine, Science, This Day in History · Comments Off on Jonas Salk’s 100th Birthday 

The History of Polio is forever and inextricably linked with  Jonas Salk . Salk’s eagerly anticipated achievement of inoculation against the much feared polio virus was made public on April 12, 1955

Not long after the announcement of the success of the Salk Vaccine , Jonas appeared in what would become a well-known television interview with Edward R. Murrow. When Murrow asked why he did not obtain a patent on his medical discovery, Salk famously said in response, “Would you patent the sun?” His response left the impression that it was a morally motivated decline on Salk’s part that resulted in an unpatented invention. But there are other details that point to the possibility of an altogether different reason having less to do with Salk and more to do with other factors  apart from Salk’s refusal to apply for a patent.

October 28, 1914 marks the 100th anniversary of Jonas Salk’s birthday.

1985 Interview with Salk

Ebola Virus: One of Its Most Deadly Forms

March 26, 2014 · Posted in Medicine · Comments Off on Ebola Virus: One of Its Most Deadly Forms 

The history of the Ebola virus is believed to date back to the beginning of our planet, though it was only first discovered in 1976. A clue that indicates an ancient origin is that the molecule’s genetic code is one of the most primitive and ancient  having a single strand of RNA. The Hot Zone

The recent outbreak of Ebola in West Africa, upon careful DNA analysis, is determined to be of the most deadly of the Ebola viruses known as the Zaire strain. This version of the Ebola virus typically kills up to 80 percent of the victims it infects. The name is derived from the 1976 outbreak in northern Zaire; for the Ebola River in Zaire (see table below from WHO International for exact number of deaths)

It takes only a small number of particles contracted through Blood-borne pathogens for an “extreme amplification” to erupt in Ebola Zaire’s host.


Table: Chronology of major Ebola haemorrhagic fever outbreaks (as of May 2012)


Year Country Virus subtype Cases Deaths Case fatality
2011 Uganda Ebola Sudan 1 1 100%
2008 Democratic Republic of Congo Ebola Zaire 32 14 44%
2007 Uganda Ebola Bundibugyo 149 37 25%
2007 Democratic Republic of Congo Ebola Zaire 264 187 71%
2005 Congo Ebola Zaire 12 10 83%
2004 Sudan Ebola Sudan 17 7 41%
2003 Congo Ebola Zaire 35 29 83%
2003 Congo Ebola Zaire 143 128 90%
2001-2002 Congo Ebola Zaire 59 44 75%
2001-2002 Gabon Ebola Zaire 65 53 82%
2000 Uganda Ebola Sudan 425 224 53%
1996 South Africa (ex-Gabon) Ebola Zaire 1 1 100%
1996 Gabon Ebola Zaire 60 45 75%
1996 Gabon Ebola Zaire 31 21 68%
1995 Democratic Republic of Congo Ebola Zaire 315 254 81%
1994 Cote d’Ivoire Ebola Ivory Coast 1 0 0%
1994 Gabon Ebola Zaire 52 31 60%
1979 Sudan Ebola Sudan 34 22 65%
1977 Democratic Republic of Congo Ebola Zaire 1 1 100%
1976 Sudan Ebola Sudan 284 151 53%
1976 Democratic Republic of Congo Ebola Zaire 318 280 88%

The Ebola Zaire strain

The Bubonic Plague is Alive and Well

March 8, 2014 · Posted in Medicine · Comments Off on The Bubonic Plague is Alive and Well 

When we think of the plague, we imagine ages gone by, the middle ages in particular, safely contained inside the texts of detailed accounts in history books. Most of us don’t associate the plague with current times, but the truth is 10 to 20 people in the United States contract plague each year. In fact, infected mice  from a lab in New Jersey escaped in 2005 and have never been found.

In the news recently, we are warned of an increased risk of ancient diseases thawing back into existence; the Bubonic plague being one. An example is a 30,000 year old virus that has been brought back to life from its Siberian permafrost tomb. Scientist believe  that we could be vulnerable to more of these frozen enemies as climate change thaws out our planet.

The Black Death

March 8, 2014 · Posted in Medicine · Comments Off on The Black Death 
The Black Death

Hulton Archive/Getty Images
The Black Death in a European town


430 B.C.- During the second year of the Peloponnesian War, Thucydides writes about a disease that is believed to have been the Plague

540 A.D.- An outbreak of Plague occurs at Pelusium, Egypt.

542 A.D.- Plague reaches Constantinople.

1334- Plague occurs in Constantinople

1339-1346- The famine occurs. This goes on for seven years and is known as “the famine before the plague.”

1347- The Black Plague began spreading through Western Europe

Fall 1347- Reports of the plague are recorded in Alexandria, Cyprus, and Sicily.

Winter 1347- Plague then reaches Italy.

Jan. 1348- Next, the plague reaches France and Germany.

1349- 1/3 of the population in Western Europe was dead from the plague. That is roughly 25 million people.

May 1349- It then reaches Norway.

1350- Afterwards the plague reaches Eastern Europe. More specifically, it reaches London, Scotland, Wales, and Ireland.

1351- The plague reaches Russia.

1353- Giovanni Boccaccio finishes writing The Decameron, a fictional narrative that opens with a description of the 1348 outbreak of Black Death in Florence, Italy.

March 1665- The Great Plague of London begins, and 43 people died by May.

June 1665- 6,137 people die by June.

July 1665- 17,036 people die by July.

Aug. 1665- 31,159 people die by August.

1666- The Great Fire of London destroys most of the rats and fleas that carry the plague bacillus.

1679- The plague devastates central Europe.

1711- Plague breaks out in Austria.

1722- Daniel Defoe publishes A Journal of the Plague Year, a fictional recounting of the great Plague of London in 1665.

1770- The Balkans battle the Plague for two years.

1877: The pandemic starts up again and flares up in Russia, China, and India.

1889: The Pandemic begins to near an end.

1894: Working independently, bacteriologists Alexandre Yersin and Shibasaburo Kitasato both isolate the bacterium that causes the Black Death. Yersin discovers that rodents are the mode of infection. The bacterium is named Yersina Pestis after Yersin.

1896: The pandemic in China and India is over.

1947: Albert Camus publishes The Plague, a novel about a fictional outbreak of plague in Oran, Algeria.

Sept. 2005: Three mice infected with Bubonic Plague disappear from a laboratory at the Public Health Research Institute in New Jersey.

SARS Virus

January 6, 2014 · Posted in Medicine · Comments Off on SARS Virus 

Tracking SARS back to its source January 2006

The previously unknown SARS virus generated widespread panic in 2002 and 2003 when the airborne germ caused 774 deaths and more than 8000 cases of illness. But where did this mystery virus come from? Scientists immediately suspected that it had jumped to humans from some other organism. In May of 2003, attention focused in on cat-like mammals called civets. Infected civets were discovered at a live animal market in southern China (where they are occasionally eaten). However, since further searches failed to turn up more tainted civets, scientists concluded that they were not the original source of SARS and continued their quest. Then in the fall of 2005, two teams of researchers independently discovered large reservoirs of a SARS-like virus in Chinese horseshoe bats. The bats now appear to be both culprit and victim in this mystery: they are the carriers of the SARS virus, but the virus is probably only passed to humans through intermediate hosts when bats are captured and brought to market.

Where’s the evolution? How exactly did biologists conclude that bats, and not civets, were the original source of the SARS virus? Figuring out the answer required reconstructing the evolutionary history of the virus.

Viruses evolve rapidly and constantly, changing within a lineage and splitting off to form new lineages. As they evolve, they accumulate small changes in the sequences of their genomes. Based on these genetic differences, biologists can reconstruct the evolutionary relationships of different viral strains, building an evolutionary tree that reveals which strains evolved from which strains and in what order they evolved.

In this case, biologists collected samples of the SARS virus’s genetic material, RNA, from different sources: infected humans, infected civets, and different species of infected horseshoe bat. The RNA was then copied, sequenced, and used to build a phylogeny, or evolutionary tree.

The tree showed that civet and human SARS viruses are very similar to each other and, most importantly, that both are nested within a cladeof bat viruses — so the ancestor of the civet and human strains seems to have been a bat virus! Based on this evidence, biologists have come up with a plausible path of transmission: infected bats and uninfected civets came into contact at a market, the virus was transmitted to civets and then multiplied and evolved in civets (or other animals) in the public market, until eventually the virus hopped to humans.

Interestingly, viruses seem to frequently make the jump from bats to human hosts. Bats appear to be the natural reservoirs for many human viruses, including the Ebola, Hendra, and Nipah viruses — and now we can add SARS to that list. But what is it about bats that makes them such a common source of viruses? Well, biologists aren’t sure, but it might have something to do with their tendency to roost tightly packed in caves with other bat species. This situation might encourage the transmission of viruses between individuals and species and provide opportunities for viruses to evolve and recombine with each other — much as biologists fear the avian flu will recombine with a human flu virus and evolve into a deadly, epidemic-causing strain.

Knowing that human SARS ultimately evolved from a bat virus can help us better understand emerging diseases and find ways to prevent future outbreaks. Certainly, we must limit contact between bats and humans and bats and other animals. However, such viruses have existed in wild animal populations for a long time — why are they suddenly evolving to infect human hosts? The answer probably has to do with changes in human behavior: expanding human populations encroach on the territory of wild animals; markets, farms, and ranches often bring different species together in conditions that facilitate pathogen spread; and increased travel and trade between tropical regions and other areas of the world carry pathogens to new environments. Understanding these paths of transmission may help us prevent future outbreaks of diseases such as HIV, SARS, and West Nile virus — all of which have made the leap from wild animals to human hosts.

Read more about it

Primary literature:

  • Lau, S.K., Woo, P.C., Li, K.S., Huang, Y., Tsoi, H.W., Wong, B.H., Wong, S.S., Leung, S.Y., Chan, K.H., and Yuen, K.Y. (2005). Severe acute respiratory syndrome coronavirus-like virus in Chinese horseshoe bats. Proceedings of the National Academy of Sciences USA102(39):14040-14045.
  • Li, W., Shi, Z., Yu, M., Ren, W., Smith, C., Epstein, J.H., Wang, H., Crameri, G., Hu, Z., Zhang, H., Zhang, J., McEachern, J., Field, H., Daszak, P., Eaton, B.T., Zhang, S., and Wang, L.F. (2005). Bats are natural reservoirs of SARS-like coronaviruses. Science 310(5748):676-679.

News articles:

Understanding Evolution resources:

Discussion and extension questions

  1. What do evolutionary trees represent?
  2. What did the phylogeny of SARS virus strains indicate to researchers?
  3. What evidence did researchers use to build the phylogeny of SARS virus strains? List two other types of evidence that could be used to build an evolutionary tree.
  4. Read the short article Evolution and the avian flu. Using the concepts of viral evolution introduced in that article, explain some possible ways that bat SARS could become adapted to human hosts.
  5. Research another case of an infectious disease that has evolved from a strain originally infecting a wild animal population (e.g., HIV). Explain how that disease made the jump to humans and how that “host switch” is similar to and different from the emergence of SARS.

Related lessons and teaching resources

  • Teach the basics of phylogenetics. In this web-based module for grades 6-12, students are introduced to cladistics, which organizes living things by common ancestry and evolutionary relationships.
  • Teach about how phylogenies are built. This classroom activity for grades 9-12 introduces how cladograms are built using anatomical characters and shows how shared derived characters can be used to reveal degrees of relationship.
  • Teach about using molecular data to infer evolutionary relationships. In this classroom activity for grades 9-12, students formulate explanations and models that simulate structural and biochemical data as they investigate the misconception that humans evolved from apes.


  • Lau, S.K., Woo, P.C., Li, K.S., Huang, Y., Tsoi, H.W., Wong, B.H., Wong, S.S., Leung, S.Y., Chan, K.H., and Yuen, K.Y. (2005). Severe acute respiratory syndrome coronavirus-like virus in Chinese horseshoe bats. Proceedings of the National Academy of Sciences USA102(39):14040-14045.
  • Li, W., Shi, Z., Yu, M., Ren, W., Smith, C., Epstein, J.H., Wang, H., Crameri, G., Hu, Z., Zhang, H., Zhang, J., McEachern, J., Field, H., Daszak, P., Eaton, B.T., Zhang, S., and Wang, L.F. (2005). Bats are natural reservoirs of SARS-like coronaviruses. Science310(5748):676-679.
  • Normile, Dennis. (2005). Researchers tie deadly SARS virus to bats. Science309:2154-2155.
  • The usual suspects. (2005, November 17). The Economist. Retrieved December 19, 2005 from The Economist.

Civet photo provided by MCPA2; bat photo provided by Dr. Brock Fenton See Photos here

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