THE SPREAD OF VIRAL INFECTIONS
Subject: Health; Science/Biology;
Ages: 14+: High School;
Length: 33 minutes in five film clips or 53 minutes in one clip.
These film clips are designed to supplement existing lessons on the spread of viral infectious disease.
Using the Snippet in Class:
Students will have a clear picture of the path that a virus could take from a host animal to its first human victims and from there to an epidemic that could destroy an entire community.
The film clips provide an excellent supplement to a unit on the spread of infectious disease.
A deadly virus is transmitted from Africa to the United States and threatens to cause an epidemic. The clips are taken from the first hour of the movie showing how the disease spreads.
THREATS TO HUMAN HEALTH PRESENTED BY VIRUSES
When it was discovered that bacteria could cause disease, there were many illnesses for which bacterial agents could not be found. These included serious diseases such as smallpox, polio, rabies, and influenza, as well as less serious maladies such as the common cold. These diseases and many more are caused by viruses.
Viruses are infectious agents which are between 20 and 100 times smaller than bacteria. They are too small to be seen through a normal microscope and can be visualized only through an electron microscope. Viruses consist of strands of genetic material (RNA or DNA) surrounded by a coating of protein (called a capsid). Viruses are not considered to be living organisms because they cannot reproduce outside of a living cell.
A virus binds to a cell when a part of the outer viral structure docks with a specific molecule on the cell surface. It then crosses the cell wall through a variety of methods (for example, injecting its genetic material through the cell wall or incorporating its capsid into the cell wall).
Viruses multiply by inserting their genetic information into a cell and harnessing the cell machinery to replicate the viral genetic material and make new capsids. The new viruses are then transmitted to other cells, either through the cell wall or when the cells burst and die. Viruses are parasites on a cellular level.
New strains of disease-causing viruses are a constant threat because viruses mutate easily. For example, each year a new influenza virus causes illness in millions of people. As a result, and because most drugs cannot disable a virus without harming healthy tissue, it is difficult to develop drug therapies to cure viral infections.
Viruses can be transmitted from one animal species to another. They affect each species differently and one species can harbor viruses deadly to another without any ill effect. For example, most Ebola viruses and the Hantavirus, do not cause disease in their host animals, but they are deadly to man. The Ebola-Reston virus, on the other hand, is deadly to monkeys but does not cause illness in humans.
Viral illnesses can be spread in a number of ways. Some, such as AIDS and Ebola, can only be spread through exchanges of blood or other bodily fluids. Others, such as influenza and the common cold, are airborne and enter through the respiratory tract. The Hantavirus is spread by breathing dried rodent feces which become airborne.
The Ebola virus is in the shape of a long rod, usually 800 to 1000 nanometers long. (A nanometer is one billionth of a meter.) The virus consists of a coiled strand of ribonucleic acid (RNA) contained in an envelope derived from the host cell membrane. The envelope is covered with spikes that are used by the virus to gain entry to new host cells. There are several strains of Ebola virus of varying degrees of mortality. The most fatal is Ebola/Zaire which kills 88% of those infected. The virus is called “Ebola” because it was first discovered near the Ebola river in Zaire.
Ebola hemorrhagic fever is characterized by a severe headache, weakness and muscle aches, followed by abdominal pain, diarrhea, inflammation of the throat, eyes and mucous membranes, bleeding from body openings and destruction of internal organs. The incubation period is usually 5 to 10 days. The course of the disease is usually 7 to 10 days if it proves fatal. Between 12% and 50% of the victims will survive, depending on the strain of the virus. There is no known cure. In Zaire in 1995, blood from patients who were recovering was transfused into severely ill patients in an attempt to transfer antibodies to neutralize the virus. This technique met with some success, but clinical trials have yet to be conducted. Conventional treatment consists of preventing shock and providing supportive care. Care must be taken to prevent the spread of the illness to health care workers. Convalescence takes five weeks or more.
The first identified outbreaks of Ebola occurred in 1976, one in Zaire and one in Sudan. There were about 550 cases and 430 deaths. Another outbreak occurred in the city of Kitwit, Zaire in 1995 affecting 315 people and killing 242. There have been isolated cases of Ebola in various places in Africa. Ebola spreads when a person becomes infected from an animal reservoir host and then spreads the disease to other humans. The host and natural transmission cycle for the Ebola virus remain unknown.
There are historical precedents for many of the events described in the film. For example, neither smallpox nor the common cold existed in the Americas before the Europeans came. The indigenous population had not developed any genetic resistance to these viruses. Europeans brought these diseases with them, unintentionally causing pandemics which destroyed more than 3/4 of the population of some Native American tribes. It is believed by historians that the reason that the Spanish explorer Cortez, with only three hundred men, could conquer the massive and powerful Aztec empire was the spread of smallpox.
In 1989, a deadly virus from Africa, the Lassa virus, was brought to the U.S. by a man who had traveled to Africa to attend the funerals of his parents, both of whom died from an illness thought to be caused by the Lassa virus. After the man flew home, he became ill, going to a suburban Chicago clinic complaining of fever and a sore throat. The doctors gave him antibiotics and sent him home where he died of Lassa fever. Fortunately, no one else became infected, partially because of improved sanitation precautions at the clinic imposed to restrict the spread of AIDS. There was also an outbreak of a strain of Ebola virus that was fatal to monkeys but fortunately not to humans at a primate quarantine facility in Reston, Virginia in 1989.
Hantaviruses infect vertebrates and are usually transmitted by dried rodent feces blown into the air as dust. Hantaviruses cause two different human diseases: hemorrhagic fever with renal syndrome, in which damage to the kidneys is common, and acute respiratory distress syndrome, in which damage to the lungs is common. Hantaviruses were first identified in the Korean War when thousands of United Nations soldiers became ill with fever, headache, and acute renal failure. Outbreaks in the American Southwest have been the most recent occurrences of Hantavirus infection.
1. Read the Helpful Background section of this Guide.
2. Be familiar with the location of the clips on the DVD, check for accuracy of the minute and second locations of the clips on the DVD, and practice getting quickly from one film clip to the other. Each of the clips starts at the beginning of a chapter of the DVD. This makes it easy to transition to the beginning of each clip. However, the teacher will have to be vigilant as to when to end the clips. An alternative is to simply play the film from Chapter 2 (when the film starts and the Warner Brothers Logo appears on the screen, skip to Chapter 2, minute 3:55) until the end of clip #5, minute 55:35, which will take about 53 minutes. If you select this alternative, you may ignore the remaining instructions in this step. However, be sure to stop the movie at 55:35 as Sam tells General Ford “And if one of them has got it then ten of them have get it. . . .” There’s good dialog for the next few seconds but it’s a little profane.
Clip #1: Chapter 2: Minute 3:55 to 7:05 (3 minutes, 50 seconds). When the film starts and the Warner Brothers Logo appears on the screen, skip to Chapter 2 (minute 3:55) The screen will be all black except for the words “Present day. ” Allow the movie to run for another 3:50 minutes until minute 7:05 which is the end of the chapter. The last scene shows Sam and Robby in the Level 4 facility working. At 7:05, just before the scene shifts to Sam’s house and the audience would hear him talking to his dogs, skip to Chapter 4. Chapter 3 deals with the subplot of the relationship between Sam and Robby.
Clip #2: Chapters 4 – 6: Minute 10:25 to 20:32 (10 minutes, 7 seconds) These chapters show the trip to Zaire to bring back samples of the Motaba virus. Chapter 4 begins when the army unit is shown loading the plane at minute 10:25. Chapter Six ends at minute 20:32 just after the Chinese sailor is feeding the host a banana. At that point skip to Chapter 8. Chapter 7 deals with the relationship subplot.
Clip #3: Portion of Chapter 8: 23:07 to to 26:45 (3 minutes 38 seconds). This clip starts at the beginning of Chapter 8. The first part of this chapter shows the conversation between Sam and Casey about Sam’s divorce. Sam is so distracted that he misses the fact that his suit is ripped, a mistake that could have led to his death when he entered the level 4 facility. It also shows a view of the virus. Stop at 26:45, after Sam says, “Kill it.” The scene then shifts to Major Ford going into the containment facility. The rest of Chapter 8 and Chapter 9 are the introduction to the fact that the Army has been developing a serum with antibodies to the virus with which to protect its own troops if it ever wants to use the virus as a biological weapon. The officer in charge is willing to allow thousands of civilians to die to protect the secrecy of the Army’s research. At 26:45 skip to Chapter 10.
Clip #4: Chapters 10 – 13: Minutes 30:25 – 40:38 (10 minutes 13 seconds) These chapters start with Jimbo taking the host through the Biotest Animal Holding Facility with the help of a bribed guard. They continue with the trip to the pet shop in Cedarville, Jimbo letting the monkey go free in the forest, and various deaths and infectious transmissions, culminating in an airborne transmission in a theater. Chapter 14 is about the effort to keep Sam contained so that the Army’s secret cure for the disease will not be discovered.
Clip #5: Chapters 15 – 17: Minutes 47:22 to 55:35 (8 minutes 13 seconds). This shows how the doctors attempt to trace the infection, how Sam discovers that the virus has become airborne, and the discovery of a second strain. Stop the movie at minute 55:35 as Sam tells General Ford ” And if one of them has got it then ten of them have get it. . . .” The dialog during the next few seconds is a little profane.
1. Before showing the film, write on the board or tell students that, “‘The single biggest threat to man’s continued dominance on the planet is the virus.’ Joshua Lederberg, Ph.D., Nobel Laureate” Tell students that they will be asked to come up with an answer about whether this is a true statement.
2.–– Unless you will be using the single slip of 53 minutes, tell students that the scenes you will be eliminating relate elements of the plot that don’t directly concern the transmission of infectious diseases. Some concern a subplot which tells the story of Sam’s distress at the breakup of the marriage of Sam and Robby and who will have custody of their pet dogs. They used to work together but now they hold similar positions as the leader of a team of scientists charged with protecting the public from infectious diseases. She is at the Centers for Disease Control and he works for the Army Medical Research Institute of Infectious Diseases (USAMRIID).
3. Show the film clips to the class.
4. After showing the clips, remind the class of the question posed before the film was shown and take answers.
“‘The single biggest threat to man’s continued dominance on the planet is the virus.’ Joshua Lederberg, Ph.D., Nobel Laureate”
Suggested Response:
Viruses can be lethal and they frequently mutate, making it difficult to develop ways to fight them.
5. Concluding Assignment Suggestions: Students can be assigned to research and write papers on the following topics: (1) the Centers for Disease Control and its role in preventing the spread of communicable disease (the CDC is generally responsive to requests by students for information); (2) the path of the “Motaba” virus from reservoir host to epidemic as shown in the movie; (3) how the destruction of the rain forest could help to create new strains of disease; (4) whether the government has legal authority to eradicate an entire town for the purpose of preventing the spread of a deadly contagious disease to the entire nation; (5) the history of quarantine as a device for preventing the spread of disease; (6) the role of mutation in the spread of viruses; (6) the different means of diagnosing viral diseases such as Ebola; (7) why it is difficult for a vaccine to be created to stop a virus; and (8) why viruses are thought to be one of the greatest threats to human dominance of the planet.
This Snippet Lesson Plan was written by James Frieden. It was published on March 28, 2012.
Using the Snippet in Class:
See Preparation Step #2.
For a film that contains some information about the transmission of viral diseases and which provides a realistic forecast of the response of the public health agencies and society in the event of an influenza pandemic, see Contagion.
TWM does not recommend showing the entire movie. After clip #5 the film’s science starts to deteriorate. In addition, the movie is rated R for profanity; however, in TWM’s opinion that is an undeserved rating.
The Hot Zone by Richard Preston; Level 4: Virus Hunters of the CDC, by Joseph B. McCormick (former head of the CDC’s special pathogens branch) and Sue Fisher-Hoch; and Ebola, by William Close are excellent books to accompany the study of the transmission of infectious diseases. McCormick, for example, is one of the few physicians who has treated patients with Ebola. He calls Close’s novel “the best researched and thus the most accurate account of all the events that took place … in 1976 [in the African Ebola outbreak].” We have not read any of these books nor have they been recommended to us for children
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