Over the past couple of weeks, I’ve been doing a unit on infectious diseases with our little co-op. I get the impression that some folks have co-ops that do quite formal learning and provide whole sections of the curriculum for the kids. Ours is more informal. We get together in someone’s house once a week for a couple of hours. Our kids range from 8 to 12 years old. The idea is that there is a learning activity for about an hour and then the kids get to play together. That learning activity can be anything including board games and crafts. This year we organized it in blocks of 3 weeks so that we could do more substantial things but those things vary considerably. I picked the topic out of the air.
These notes are mostly for the kids in case they want to do any more work on these issues or review anything we talked about.
Infectious diseases are those diseases that can pass from one person to another. Examples include the common cold, flu, and chickenpox. It is the fact that you can pass them on that makes them “infectious”.
Keywords for week 1:
- pathogen – from the Greek “pathos” (disease, suffering) and “genos” (origin), the collective term for the things that cause disease, these can include bacteria, viruses, fungi, parasites.
- Bacteria – single celled organisms, some cause diseases (for example, strep throat is caused by bacteria)
- Virus – a protein that can get other cells to reproduce it, some cause disease (for example, colds and flu are caused by viruses)
- immune system – the various ways that your body fights off pathogens including the barriers to their entry into your body and the white blood cells that kill pathogens
- antibodies – proteins produced by your bodies to mark pathogens so your white blood cells know to kill them
- vaccine – a weakened form of an infectious disease introduced to encourage your body to produce antibodies so that if you ever come in contact with the real disease, your body can fight it off before you get sick
BrainPop has movies about bacteria (check out the FYI link on the bottom of the page for more detailed information), viruses, and the Immune System. Unfortunately, you need a subscription though there is a 5 day trial. We have a subscription so if there is something on there you really want to watch, let me know.
National Geographic has some cool information and quizes about bacteria.
There are good diagrams and explanations of all your body systems at the Sick Kids site. If you go to respiratory system, there is a tab for “defense” that explains the first line of defense against infections.
Keywords for Week 2:
- vector – word used to describe transmission of disease via another organism (for example, malaria is transmitted between humans by mosquitos)
- incubation period – the period of time between exposure to a pathogen and the pathogen reproducing itself enough to make you sick
- contagious period – the period of time in which you can pass on the pathogen to someone else
- antibiotic resistance – mutations of bacteria that are not killed by (certain) anti-biotics, such bacteria are sometimes called “super bugs”
- mutation – a mistake in the copying of the DNA during reproduction; mutations might make an organism weaker and it dies before reproducing again, have no discernable effect, or give it advantages that makes it last longer and reproduce more than other strains of the organism;
There is good general information about infectious diseases and the ways they can be passed on here.
The table of incubation periods and contagious periods that I showed you was based on information found here. The important thing about this is that for many infectious diseases, you are contagious before you even know you are sick. And those who have caught the disease won’t know that they have caught it until the end of the incubation period, which might be several weeks.
The main modes of transmission are:
- air (for example, colds can be transmitted through the air when you sneeze)
- direct contact (depending on the disease this may be getting pathogens on your hands from touching someone else or from touching something that has pathogens on it, like a door knob; some diseases, like HIV/AIDS, are much harder to catch and require very intimate forms of direct contact)
- water (for example, polio and cholera)
- vector (for example, malaria, bubonic plague, West Nile virus)
To prevent disease it is important to think about the mode of transmission. So for airborne transmission, we want to prevent pathogens from remaining in the air. We can cover our mouths when we cough or sneeze, or even wear a mask over our mouth and nose.
For direct contact, we need to keep surfaces clean and wash our hands regularly. Because the skin on our hands is very good at preventing pathogens from entering our bodies, they are often not an immediate danger to us, but we should keep them away from our faces, where there are more ways for the pathogens to get in. It is also important to keep cuts clean as they are breaks in that skin defense. Barriers like gloves are used by medical staff for this purpose.
Water borne transmission is prevented by major public works like sewage systems and water treatment systems. When you are camping, you might prevent water borne diseases by boiling water for 20 minutes and letting it cool before you drink it. Many pathogens are killed at high temperatures though it may take several minutes for them to die.
Vector transmission can be prevented by keeping the carriers of disease separate from human populations. Clearing up sources of food (as in the case of rats and the plague) or the conditions in which they reproduce (as we do when we try to eliminate stagnant water to prevent West Nile disease and malaria) work well. As do barriers to human contact with the vectors like mosquito nets and insect repellent.
The level of precaution necessary depends on the level of risk. Your immune system is very good at repelling pathogens and at killing them before you get sick. But there are circumstances when your immune system will be weaker: when you are already ill, when you are very young (babies), when you are older, or if you have a condition that weakens your immune system. Your immune defenses will also be weaker if you are very tired or you are not eating properly. If ever you are visiting someone who might have weaker immunity to disease you should take extra precautions to prevent passing disease to them.
Remember, most of the bacteria, viruses and fungi that you come in contact with in daily life are not harmful and may be beneficial. I hope everyone enjoyed themselves. Remember we are meeting at the library next week.