LECTURE OUTLINE #3:  The Ebola Virus and other diseases

 

 

I.  THE THREE PANDEMICS OF THE 20TH CENTURY

1.  1918-20, “Spanish flu,” caused 500,000 deaths in USA and 50 M in the world.

2.  1957-58, “Asian flu,” (from China) caused 70,000 deaths in USA and 3 M worldwide.

3.  1968-69, “Hong Kong flu,” kills an estimated 36,000 people in the USA each year.

 

II.  VIRUSES WITHIN THE TIMELINE OF EVOLUTION OF LIFE ON EARTH

1.  The of evolution of viruses.  (began 4,000 Myr ago)

2.  Viruses are "stripped-down" parasites that co-evolve with their hosts.

3.  Viruses only need specific attachment proteins on their surface that can bind to specific receptor sites on bacteria (bacteriophages) and animal or plant cells.

 

III.  EBOLA (Filoviridae)

(Reading:  www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola.htm)

A.  INTRODUCTORY REMARKS ABOUT EBOLA.

1.  Ebola is a virus named after a river in the Congo, its first site of discovery (1976).

2.  The virus specifically attacks liver cells and the "reticuloendothelial system."

      (reticuloendothelial system is mainly macrophages and endothelial cells)

 

B.  GENERAL CHARACTERISTICS OF THE DISEASE

1.  Ebola is spread through close personal contact with an ill person.

2.  The incubation period is about 7-14 days (but can be 2-21 days)

3.  Infections are fatal in 60% (Ebola Sudan) to 90% of (Ebola Zaire) of the cases.

4.  There is no cure, or vaccine--the only treatment is supportive.

(NOTE:  careful management of fluid and electrolyte balance is critical)

5.  The epidemiological history is rather sketchy:

a.  1976, the first epidemic was Ebola Zaire (killed 90% of 277 victims in Congo)

b.  1976, the second epidemic in Sudan (Ebola Sudan) (killed 53% of 280 victims)

c.  1995, the Ebola Zaire outbreak in Kikwit, Congo, killed 245 people

d.  More than 1,000 people have died since 1976.

 

C.  PROSPECTS OF A "Super-Ebola" PANDEMIC

1.  Experts say that more Ebola outbreaks are inevitable.

2.  One of the principal concerns is the mutation of an airborne strain of Ebola.

3.  Another concern is if an infected Red Cross or WHO worker travels to an urban area.

4.  Epidemiologists say that airborne variety could spread globally in 6 weeks.

IV.  AVIAN INFLUENZA “Bird Flu”, i.e., the H5N1 subtype of influenza A

(NOTE:  The information below on Bird Flu is primarily from the following website:

http://www.cdc.gov/flu/avian/facts.htm , or enter “bird flu” at www.google.com .

1.  Bird Flu makes domestic birds (but, not wild-type) sick, but usually does not infect humans.

2.  Human symptoms are fever, cough, sore throat, muscle aches, eye infections, pneumonia, acute respiratory distress, and viral pneumonia.

3.  1997 Bird Flu incident that infected 18 people in Hong Kong, with 6 deaths.

4.  2003 Bird Flu outbreak affected 80 people in the Netherlands, but only one died.

5.  As of 01/21/05, there were 52 human cases in Vietnam and Thailand, with 37 deaths.

           

V.  WEST NILE VIRUS

(NOTE:  The information below on West Nile Virus is primarily from the CDC website)

1.  West Nile virus first appeared in North America in 1999, and is now in most states in USA.

2.  It now causes summer epidemics when mosquitoes feed on infected birds, and then humans.

3.  During the year 2006, there were 4180 USA cases, with 149 deaths.

4.  80% of people who are infected do not show any symptoms at all.

5.  When symptoms appear (after 3-14 days of incubation), they include fever, headache, body aches, nausea, vomiting, swollen lymph glands, skin rash on the chest, stomach and back.

6.  The more severe cases include symptoms of stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.

 

VI.  SARS , i.e., SEVERE ACUTE RESPIRATORY SYNDROME

(NOTE:  The information below on SARS is primarily from the CDC website:)

1.  SARS is a respiratory illness that first appeared in Asia in February 2003, i.e., 4 year ago.

2.  During an epidemic in 2002-03, 8,098 people in world became infected, and 774 died.

3.  Symptoms include general flu symptoms, sometimes diarrhea, and oftentimes pneumonia.

4.  SARS is spread by close person-to-person contact, or from infected persons coughing/sneezing.

5.  Last significant SARS transmission was in April, 2004, in China.

 

VII.  MAD COW DISEASE , i.e., BOVINE SPONGIFORM ENCEPHALOPATHY (BSE)

(NOTE:  The information below on Mad Cow is primarily from the CDC websites)

1.  BSE is a progressive neurological disorder with a long incubation period—in the order of years.

2.  The bovine type (i.e., BSE) and the human type are invariably fatal.

3.  The infectious organism, or method of transmission, has not been identified.

4.  Theory is that infection involves changes in a normal cell surface protein called a “prion”.

5.  Outbreak of disease appears to be associated with feeding cows sheep meat-and-bone meal.

6.  On December 23, 2003, the first diagnosis of a cow in USA.  (03/13/06 in Alabama)

7.  Estimated that more than 188,000 cows have been infected and 170 humans (mostly in U.K.).

8.  BSE has cost the USA beef industry ~$3 billion.

 

(NOTE:  For more information on any common diseases, go to the A to Z list at the CDC.)

 

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