microorganism - A microorganism (also called a microbe) is a microscopic (or sub-microscopic) organism, such as a bacterium, virus, and others.

mutate - To mutate is to undergo a change. Viruses mutate frequently as they reproduce, SInce their genetic makeup is slightly different all the time, creating flu vaccines is a continual challenge.

respiratory system - The respiratory system is the system in the body that takes in oxygen and gives off carbon dioxide. Our respiratory system consists of the lungs and airways. The flu virus infects the respiratory system.

RNA - RNA (which is short for ribonucleic acid) is genetic material found in cells. RNA contains the codes for protein synthesis (making proteins) in the cell.

strain - A strain is a particular type of related organisms. Different strains of flu viruses have different rate of contagiousness and cause different death rates among people.

symptom - A symptom is an abnormal functioning of the body that indicates that you may have an illness. The symptoms of the flu include high fever (over 100 °F), cough, sore throat, stuffy or runny nose, muscle pain, and weakness.

vaccine - A vaccine is a medical preparation that gives you immunity to a specific disease. There are flu vaccines that help protect people from certain strains of the flu. See your doctor for advice about vaccinations.

virulent - Virulent means being very infectious or having a very harmful effect. Some viruses are more virulent than others and kill more people.

virus - A virus is a simple microorganism that cannot reproduce unless it is in a cell it has invaded. A virus consists of genetic material (RNA or DNA) with a protein coating. Viruses cause colds, chickenpox, measles, mumps, flu, and many other diseases. The flu virus consists of RNA encapsulated with protein.

Related Activities and Worksheets

The Flu Read about the flu (influenza), how it spreads, how to limit its spread, and how to protect yourself.	Influenza Definition: Comprehension Quiz Worksheet A printable worksheet in which the student answers 8 multiple-choice questions on the definition of influenza (the flu). The questions test the student's understanding of the definition of the word, the use of the word in context, the type of word it is (noun, verb, etc.), and where the word would be found in a dictionary. This is a simple lesson in using a dictionary. Or go to the answers.	The Flu: Printable Read-and-Answer Worksheet A printable worksheet on influenza, with a short passage to read including What is the flu, How the flu spreads, How to limit the spread of the flu and protect yourself, and Questions to answer. Or go to the answers. Or go to a pdf file with the worksheet and the answers.	Write a Sentence for Each Flu-Related Word Write a sentence for each flu-related spelling word. Words: influenza, virus, sneeze, contagious, symptom, fever, pain, cough, vaccine, epidemic.
The Flu: Comprehension Quiz Worksheet A printable, 10-question multiple choice quiz about the flu. Or go to the answers.	When I Felt Sick: Draw and Write Draw a picture of yourself when you were sick and write about it. Describe what why you were sick, how you felt, and about what you do did to feel better.	Flu Spelling Word Questions Use the list of spelling words to answer simple questions about flu-related words. Words: cough, virus, fever, influenza, symptom, epidemic, contagious, recover, vaccines, microorganisms. Or go to the answers.	All About the Flu A Printable Book A printable book about the flu for fluent readers. The pages include: What is the Flu?, How the Flu Spreads, The Incubation Period, How to Avoid the Flu, Recovery, Glossary, and Questions.