I want to write a little bit about your writing projects.

First: do not worry too much about the grading of the papers. What I will mostly be looking for when I figure your grade will be improvement over the semester. After all, I want you to learn, so I wouldn’t expect everyone to be perfect right off the bat!

Also: The grade of “3” is not a bad grade. I am going to elaborate a bit on grading next…

Grade = 1

This means your paper is not readable and misses the boat.

Grade = 2

We can tell you put some effort into your paper. You might touch on an important idea, but the evolutionary concept is missing or we can’t understand the point you are trying to make.

Grade = 3

This is an ok paper. Your writing is reasonable and logical. At least one major point from the lecture or reading is apparent in your paper.

Grade =  4

At least two major points from lecture are expressed in a well-argued way.

Grade = 5

We couldn’t say it better ourselves!

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Here is what I want you to take away from the Dengue Fever lecture and writing project:

The dengue virus benefits from making its victims immobile. Immobility is usually associated with high virulence. Immobility is also a trait that benefits vector-borne diseases. As many of you mentioned, an immobile victim cannot effectively swat a blood-sucking insect. Some of you also mentioned that caretakers might also be at risk from vectors because they have to stay in close quarters with the victim.

The virus that causes the common cold generally is transmitted better when its victims are not immobile. This is because it is transmitted by direct contact, not vectors. Pathogens that are transmitted by direct contact are generally less virulent than those that are vector-borne. If the cold virus made its victims unable to move and leave the house, then it would be less likely to spread like wildfire through offices and schools and universities!

Three main modes of transmission of pathogens include, direct, vectors, and environmental.

1) Direct contact diseases (like colds) are transmitted best when the victim is active. These are generally the least virulent.

2) Vector-borne diseases usually require the victim to be alive but are better transmitted if the victim is not moving. These are usually more virulent.

3) Environmentally transmitted diseases can be the most virulent. These do not require the victim to be active. Some are like vector borne diseases (cholera), in which the attendants who wash the soiled bedclothes in the river promote transmission of the bacteria. Some do just fine even after they kill the victim (anthrax), when the corpse releases infectious spores! In general, environmentally transmitted diseases might have very high virulence.

Hospital-acquired infections are like vector borne diseases. Doctors and nurses act like mosquitos. This is not because we are always drawing blood (although we are), but because our stethoscopes and hands are in contact with an immobile victim and then we often touch another patient.  Pathogens that are quite virulent and serious may attract even more attention from doctors and nurses (buzzing around the sicker patients like mosquitos!). So for the hospital acquired pneumonia, there is no downside to becoming more virulent and making the patient more immobile. Transmission of the hospital acquired pathogen depends on interaction with vectors: hospital workers who do not always wash their hands! This is in contrast to the community acquired pneumonia. Community acquired pneumonia might require direct contact (like the cold virus) for its transmission between patients. For this reason, a hospital acquired pneumonia is generally much more serious than a community acquired pneumonia.

Got it!

If you guys have any questions about a writing project, do not hesitate to email me or Chris or talk to us after class or in Chris’s office hours.

I will put the readings for next weeks lecture on eReserve now.

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Joe Alcock

Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine