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Emerging Disease Sites:

Emerging diseases are diseases which have only begun to appear in humans, or new strains of otherwise familiar diseases which have unusually severe effects on their victims. As the human species moves into areas such as the rain forests of Africa and South America where previously humans had been rare, there are increasing opportunities for diseases such as Ebola and AIDS to develop as obscure viruses are introduced to the human population. The pattern which is thought to be developing is that most emerging diseases "jump species" from animals, or even plants, into humans - and that humans lack the evolutionary adaptations which enable their usual host species in the wild to coexist with these diseases.

The grave danger (assuming that there has always been a low level of infection and death from these diseases in the local human populations) is the relatively new availability of rapid travel by road and air from areas where emerging diseases are appearing. Diseases such as Ebola and Marburg virus that kill a large percentage of their victims within days are known informally as "slate wipers" because they have the potential, if they are spread around the world, to kill a large number of the world's people - "wiping the slate clean," to use a grim metaphor.

There has been at least one incident in which an Ebola patient collapsed from her symptoms just before she would have boarded an airliner for Europe. Fortunately, the strain of Ebola with which she was infected (Ebola zaire) was much less contagious than the Ebola reston strain, which the US Army's biological defense branch at Fort Detrick, Maryland thinks can be spread through the air. Much more recently (and ominously), the new Severe Acute Respiratory Syndrome (SARS) has spread from a single floor of a Hong Kong hotel around the world in the space of a few weeks. So far, 89 people have died worldwide from SARS and 2,416 have fallen ill of the disease, most of them (2,020 cases, 69 deaths) in China (Guangdong province and Hong Kong special administrative region).

ProMed-Mail “the global electronic reporting system for outbreaks of emerging infectious diseases & toxins” This is the Email site where physicians report outbreaks of emerging diseases to their colleagues across the world.

Reading the posts on this site gives one a sense of being where the action is – these are reports from the doctors who are actually seeing emerging diseases as they emerge.

Newsday article on the preparations National Institute of Medicine advises for new disease outbreaks, by Laurie Garrett (author of the best-selling book on emerging diseases The Coming Plague)

Severe Acute Respiratory Syndrome, or SARS is a new emerging disease caused by a virus believed to belong either to the family paramyxoviridae (labs in Germany and Hong Kong) or coronaviridae (according to the US Centers for Disease Control and Prevention, 3/24/2003). 2,416 people have fallen ill with SARS and 89 have died of it in 19 different countries as of Sunday, April 6th, 2003, according to the World Health Organization. SARS seems to have spread from one floor of a hotel in Hong Kong to people returning to their homes in the UK, Canada, Vietnam, Singapore, and Colorado, as well as throughout Hong Kong. The disease is thought to have originated in Guangdong province, China. The rapid spread of this virus was the worrisome aspect. On March 24th, only 400 people were known to be ill with SARS - by April 6th the total had increased by more than six times to 2,416. If that trend had continued (fortunately, it has not), SARS would have graduated to an epidemic, or even a pandemic (in which a significant portion of the world's population is affected - as with the strain of influenza which swept the world in the early 1900s). As it turned out, the SARS outbreak of 2003 was contained before that happened - prompt worldwide action stopped the spread of SARS at 8,098 cases, of which 774 were fatal.

The coronaviruses are a family of viruses that traditionally have caused common illnesses like colds and upper-respiratory tract infections and can be quite contagious, according to a conference call between Dr. Julie Gerberding and her colleagues at the CDC and the press on March 24, 2003. However, in humans, the most common coronavirus infection is "really, the common cold," according to Dr. Anderson of the CDC. While hypotheses exist that coronaviruses may be implicated in neurologic and gastroenterological diseases, in humans coronavirus infection is not known to be deadly in otherwise healthy victims - indicating that if the causative agent in SARS is a coronavirus, it may be an emerging virus previously not known.

The World Health Organization has confirmed that China is the country of origin for SARS. The rapid spread of the disease to Hong Kong and Vietnam suggests the infectious agent causing SARS might be airborne, meaning that the disease could spread even without face-to-face contact, according to the CDC's Dr. Gerberding.

As new cases of SARS were reported in Hong Kong, the CDC extended its travel advisory for SARS to include all of mainland China as well as Hong Kong; Hanoi, Vietnam; and Singapore. In Toronto, all hospital workers were directed to wear protective gear to stop the spread of SARS.

According to Dr. Julie Gerberding of the Centers for Disease Control and Prevention, the evidence that SARS is caused by a previously unknown coronavirus is increasing. Not only have polymerase chain reaction (PCR) assays of affected tissue from SARS patients come up positive for the suspect coronavirus in question, but CDC has observed a patient who had no antibodies for the suspect virus at the very beginning of his illness, and had developed those antibodies near the end. To date, no diagnostic laboratory test exists for SARS which is reliable early in the disease process.

The paramyxoviruses, the family to which researchers in Germany and Hong Kong first thought was the cause of SARS, cause a number of diseases (including measles) that usually involve respiratory symptoms.In Malaysia in 1999, another paramyxovirus called Nipah caused an eight-month long outbreak of illness (the main symptom of which was brain inflammation), infecting 265 people and killing 105. Nipah appears to have jumped species from pigs, as most of the people affected had prior contact with pigs. A second paramyxovirus called Hendra caused three small outbreaks in Australia in the 1990s. Some of those victims had contact with horses.

US Centers for Disease Control and Prevention page on SARS.

World Health Organization English-language page on SARS.

Ebola and Marburg, two virulent emerging viruses which cause deadly hemorrhagic fevers, belong to the family filoviridae – so named because of their rope-like appearance under the electron microscope. Early this year, Ebola spread from its original outbreak point in central Africa near the Ebola River to the Republic of Congo in west Africa, killing large numbers of people and gorillas. Until this year, Ebola had only broken out in Zaïre (the Ebola Zaïre strain) and the Sudan (the Ebola Maridi strain) in central Africa.

Ebola reston, a strain of Ebola from the Phillipines which is so far not virulent in humans, has broken out in three holding areas for cynomolgus lab monkeys in the United States and in the primate facility Ferlite Farms near Manila which supplied the monkeys. Ebola reston is named for the city of Reston, Virginia, USA, where the first outbreak of the disease occurred (Richard Preston’s book The Hot Zone is a very readable, popular-audience account of the early outbreaks of Ebola and Marburg, leading up to a detailed narrative history of the Reston outbreak).

US Centers for Disease Control and Prevention, Special Pathogens Branch page on Ebola virus - has great electron micrograph of Ebola virus particle showing the characteristic "shepherd's crook"

Table of Contents, Ebola Virus Haemorrhagic Fevers, SR Pattyn, editor. This online book contains numerous articles from the proceedings of an International Colloquium on Ebola Virus Infection and Other Haemorrhagic Fevers held in Antwerp, Belgium, 6-8 December, 1977

Ebola Virus Haemorrhagic Fevers, SR Pattyn, editor, Elsevier-North Holland, 1977 is available in low-and-high-resolution .PDF downloads here

The Big Picture Book of Viruses, ch. “the Filoviridae” – the group including deadly emerging viruses Ebola and Marburg

”Ebola and Marburg Virus Taxonomy and Morphology,” Frederick A. Murphy, Guido Van Der Groen, Sylvia G. Whitfield, and James V. Lange (Dr. Murphy - the man who first saw the Ebola virus under an electron microscope, Dr. Whitfield and Dr. Lange were with the Centers for Disease Control and Prevention, Atlanta GA, USA; Dr. van der Groen was with the Prince Leopold Institute of Tropical Medicine, Antwerp, Belgium)

New variant Creutzfeld-Jakob disease, mad cow disease, and chronic wasting disease are emerging members of a newly recognized class of illnesses – infectious spongiform encephalopathies. Older diseases such as kuru, scrapie, and visna are now thought to also belong to this class of diseases, and many other members of this deadly group are being identified. Once these diseases are detected in an animal or a human, they progress until they destroy the brain of their host, killing it.

The prevailing opinion among virologists of what causes these diseases is divided between those who accept Dr. Stanley Prusiner’s Nobel Prize-winning theory that particles called prions are responsible for the damage to victims’ brains in these diseases, and those who question the validity of Prusiner’s theory and ask whether an as yet unidentified slow virus or another cause (perhaps a molecule or crystal which might catalyze conversion of the PrP protein from its normal form to the form found in the damaged areas of spongiform encephalopathy victims) is the true disease agent.

The Official Mad Cow Disease Web Site: This site has a lot of good data, papers, resources and links concerning "mad cow disease" and similar diseases such as scrapie, kuru, and the newly publicized "chronic wasting disease" which are caused by the same strange mechanisms as mad-cow disease which I discussed above. Very helpful to people who want to know what all the fuss is about in Britain, France, and Germany... and maybe here soon.

"USDA Sued Over 'Downer' Cow Rules, by Gillian Flaccus, Associated Press": The Humane Society of the United States has sued the government for allowing some so-called "downer" cows to get into the food supply. After a case of mad cow disease was discovered in Washington state in 2004, the US Department of Agriculture prohibited the slaughter of "downer" cows - animals that cannot stand on their own - for food. A USDA rule change since then has allowed some sick or crippled cows into the food supply if they fall down after inspection by a veterinarian but otherwise seem healthy, according to the lawsuit.

My Web page on Chronic Wasting Disease (CWD), a spongiform encephalopathy which occurs in the wild population of deer and elk living in northeastern Colorado and southern Wyoming (and which is spreading across the Continental Divide to the west). There is a possibility that this disease, like mad cow disease, may be able to jump species to humans (two suspected cases of humans catching CWD in the Colorado-Wyoming area made the news here in Denver in 2002).

I plan to add additional resources on the other spongiform encephalopathies as I have time.