Simulating Viral Infections (Year 8)




  • People use science understanding and skills in their occupations and these have influenced the development of practices in areas of human activity (ACSHE136)
  • Recognising the role of knowledge of cells and cell divisions in the area of disease treatment and control 


A virus can be spread through a diversity of ways; such as contaminated water, body fluids or animal bites. Viruses frequently pass from one host to another in highly populated environments where the exchange of bodily fluids is possible. Viruses are a frequent occurrence in schools and hospitals. For example, sneezing is capable of spreading viruses across surprisingly long distances. Think of your local sports team. A player who gets a cut and is bleeding has to come off the field for their safety, and that of the other players.

The aim of this practical is to simulate viral transmission through the use of test tubes. A ‘basic’ solution is placed in one test tube while the remainder of the test tubes containing deionized or distilled water. Students will be asked to exchange their solution with three other students; mimicking viral transference in a population. Phenolphthalein indicator solution will reveal which students have become ‘infected’ with the simulated virus.


  1. Provide each student with a numbered test tube and graduated pipette. 
  2. Choose one test tube to be the “carrier” and record the tube number. 
  3. Fill all tubes with 5ml of deionized water; minus the “carrier” tube. 
  4. Fill the “carrier” tube with 5 mL 0.2 M sodium hydroxide.
  5. Place each numbered graduated pipette into its respective test tube.


Spreading the Viral Infection

  1. Select a test tube with a pipette and an index card.
  2. Write down the number of your test tube on the index card.
  3. Using the pipette, draw up roughly half of the solution and transfer it to your partner’s test tube. 
  4. Record your name and test tube number on the index card.
  5. Using the graduated pipette, mix the contents of the test tube by carefully stirring with the pipette.
  6. Repeats these steps two more times while moving throughout the classroom. Be sure not exchange fluids with the same person twice.
  7. After three transfers, place two drops of phenolphthalein indicator solution into your test tube and stir the solution with your own graduated pipet.
  8.  If the solution remains clear or turns yellow, the solution is negative for the
  9. “virus.” 
  10. If the solution turns red or pink, the solution is positive for the “virus.”

Identifying the Initial Carriers

  1. All ‘negative’ students write the numbers of their culture tubes on the board.  If this applies to you, write your number on the board. 
  2. Cross out the numbers of the ‘negative’ students on your index cards, as they cannot possibly be the original ‘carrier.’
  3. List the remaining “positive” possible carriers on the board.
  4. Negative students who exchanged solution with a positive student will be asked to identify themselves. If this applies to you, raise your hand.
  5. Cross out the numbers of these positive students from the possible list and add their numbers to the negative list on your index card. 
  6. This should reveal one to two remaining students as the original carrier. 
  7. When two are remaining; one is the original carrier and the other is the first infected student.


Following this process, students should be able to identify one to two remaining students as the original carrier. When two are remaining; one is the original carrier and the other is the first infected student.


  • Being able to identify the original carrier is a critical skill for epidemiologists in their work. When faced with epidemic viral infections, an epidemiologist will work backwards to identify the viral source. Ask students to consider how finding the ‘original carrier’ in your class ‘population compares to real cases of global epidemics. 
  • Discuss whether it would it be possible to identify who the original carrier was without the addition of phenolphthalein.
  • Explore other possible applications for this practical. Discuss whether this exercise could be used to identify an infected person with a cold or hepatitis.
  • Ask students to imagine that more exchanges occurred after the addition of phenolphthalein. Ask them if they would have exchanged with an individual who carried a potentially fatal virus, such as; HIV or HPV?
  • Challenge students to consider why bed rest is such a common recommendation for people ill with a bad cold or the flu.
  • Ask students to imagine the simulation involved the entire school population. Then, ask students whether tracing back to the original carrier would be more or less difficult.


  • Ask students to consider the implications of how international flights impact the spread of viruses around the globe.
  • Task student with researching a case of bacterial borne pathogens. A good example is; Typhoid Mary. 


icn-timer.pngTime Requirements
  1. 60 mins  


icn-material.pngMaterial List
  1. Phenolphthalein Indicator Solution, 0.5%, 5 mL
  2. Index cards, 30
  3. Sodium hydroxide solution, 0.2 M, 5 mL
  4. Marker Pen
  5. Water, distilled or deionized
  6. Paper towels
  7. Test tubes
  8. Test tube racks to hold two test tubes.
  9. Graduated Pipette, 3mL
icn-security.png Safety Requirements
  1. Wear appropriate personal protective equipment (PPE). 
  2. Ensure that students know and follow all regulatory guidelines for the disposal of laboratory wastes. 
  3. Thoroughly clean all culture tubes to remove traces of sodium hydroxide and phenolphthalein, as these materials may interfere with future results if the experiment is repeated. 
  4. Wash hands thoroughly before and after the experiment.  

icn-link.pngHelpful Links

||Biology||Classroom Practicals||General Science||Year 8||