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Infectious Diseases
Infectious Diseases

Infectious Diseases Questions

Bring on the tough stuff

1) How can you tell if you have been infected by a pathogen?

2) Why are helminth (worm) infections more prevalent in developing countries?

3) How can it be safe to have bacteria living in our gut, but dangerous to have them get into a wound?

4) How does a vaccine work?

5) Purple hair syndrome is caused by a genetic mutation in your gene for hair color. This mutation occurred when your father's sperm was created and as a result you were born with purple hair. Is purple hair syndrome an infectious disease? Why or why not?

6) How can we protect ourselves from infectious diseases?

7) Why is HIV only spread through bodily fluids?

8) Mosquitos are not pathogens. Why would mosquito netting protect somebody from Malaria?
9) Dr. Evil is looking for a new bioweapon. You are his "mad scientist" assistant. He wants to know if he should use Mononucleosis, HIV, or Smallpox. Assuming you are also evil, which disease do you tell him to use and why?

10) Why does the influenza vaccine have to be redesigned every year?

Possible Answers

1) How can you tell if you have been infected by a pathogen?
The only way to know for sure if you have been infected by a pathogen is to have special lab tests done to check for the pathogen. They can look for the pathogen directly in your blood or other body samples. Or they can look or antibodies that are specific for that pathogen. For pathogens that cause very specific symptoms, you can sometimes tell if you have been infected just by looking at the symptoms. Many pathogens have similar symptoms though, so it's best to just get a lab test done.

2) Why are helminth (worm) infections more prevalent in developing countries?

Helminth infections are spread by exposure to human feces. In developing countries many people do not have a separate place to go to the bathroom. Human feces can contaminate the water and people can come into contact with it frequently. In industrialized countries we have plumbing systems so that we never come into contact with human feces (except our own).

3) How can it be safe to have bacteria living in our gut, but dangerous to have them get into a wound?
The things that are in the gut, like bacteria, are kept separate from the rest of the body by some special barriers of cells. Even though the bacteria are "inside" the body, they are not really "in" the regular parts of the body. When bacteria get into a wound they are entering a place in the body that is sterile and bacteria are not allowed (and obviously missed the big KEEP OUT sign). They can go through the wound into the blood and damage the inside parts of the body.

4) How does a vaccine work?
A vaccine works by causing your body to make antibodies that will protect you against a disease. It does this by infecting you with a small piece of pathogen that does not hurt you. It is a safe weakened form of the pathogen, a dead pathogen, or maybe even just a tiny part of the pathogen. This pseudo-pathogen will still cause your immune system to get a little riled up, creating antibodies that will detect both the safe version of the pathogen and the "real" version of the pathogen if it ever shows up.

5) Purple hair syndrome is caused by a genetic mutation in your gene for hair color. This mutation occurred when your father's sperm was created and as a result you were born with purple hair. Is purple hair syndrome an infectious disease? Why or why not?
Purple hair syndrome is NOT an infectious disease. There is no way to "catch" purple hair syndrome and it is not caused by any type of pathogen. Purple hair syndrome is a genetic disease, NOT an infectious disease. Actually, purple hair sounds kinda cool. This doesn't really sound like a disease at all.

6) How can we protect ourselves from infectious diseases?
The following things can help you to protect you from infectious diseases

  • Frequent hand washing

  • Covering coughs and sneezes

  • Washing produce before eating it

  • Adequately cooking and/or refrigerating meats and dairy products

  • Getting vaccinated

  • Using protection during sex

7) Why is HIV only spread through bodily fluids?

HIV can only be spread through bodily fluids because it cannot survive outside of a host. It dies almost immediately upon being exposed to the outside environment. If it is transferred within bodily fluids like blood or semen, then it is not being exposed to the outside environment. HIV finds these bodily fluids warm and cozy like the inside of a body.

8) Mosquitos are not pathogens. Why would mosquito netting protect somebody from Malaria?
Mosquitos do not directly cause Malaria, but Malaria is spread by mosquitos. When an infected mosquito bites a human they can transfer the parasite into them. Since the best way to prevent an infectious disease is to prevent someone from being infected, a mosquito net is a good way to prevent infection with Malaria.

9) Dr. Evil is looking for a new bioweapon. You are his "mad scientist" assistant. He wants to know if he should use Mononucleosis, HIV, or Smallpox. Assuming you are also evil, which disease do you tell him to use and why?

You should tell him to use Smallpox because it is highly contagious, can affect anybody, and can be fatal. Also, most of the current population does not have any antibodies to smallpox since it was eradicated in 1979. It's a total sneak attack. If he uses Mono or HIV then most people will not get the disease since it is only transmitted through bodily fluids. A good bioweapon has to have something that can spread through the air by coughing or sneezing. These other diseases will also not be very fatal right away. While HIV is often fatal, it takes a long time, especially if the person is on a regular treatment plan.

10) Why does the influenza vaccine have to be redesigned every year?
Influenza mutates rapidly. This means that in a population of flu viruses there are many viruses with tiny little changes in the genome. These different viruses replicate and change a little more each time. Sometimes two strains of virus can infect the same person or animal and they can mix together to form a new virus. For these reasons, the circulating influenza strains are continually changing. Since the vaccine must be made for a specific strain of virus they must design a new vaccine each year depending on which strain is the predominantly circulating strain.

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