Google MDR tuberculosis and XDR tuberculosis.

Also, please remember that:
1. People are food to disease. Disease feeds on us. The larger the human population, the more disease will seek to eat us, the larger the disease population.
2. The more closely packed together humans are, all other things being equal, the easier it is for disease to spread.
3. Disease, our only remaining natural predators, are fought off preventively through hygiene with soap, pumped water, heated water, cooking, extermination of disease vectors (rats, mosquitos) and reactively with antibiotics, healthcare, and waste disposal. All are accomplished with cheap energy to meet the needs of 6.7 billion people.

When it becomes harder to treat or prevent infection, it won't just be a breakout of XDR TB, it will include typhoid, cholera, meningitis, flu, various hemorrhagic fevers, dysentery, hepatitis, and even plague, all of which are still being ineffectively kept in check.

How effectively will we fight disease as cheap energy declines? And how will unfolding disease outbreaks affect our ability to harness more energy?

Indeed, I think disease will have a far far bigger role to play in any sort of population reduction as the result of declining oil supplies than starvation from declining food production. Especially as third world countries become increasing urbanised, living densely in horribly unhygenic slums, it will take nothing short of a miracle to keep disease rates from skyrocketing in the coming decades. It may well be enough to keep the maximum global population as low as 8 billion (as opposed to the currently projected 9-10 billion from various organisations). While this might be better for the planet, it will be nothing short of devastating for those living in such conditions.

simply put, we wont, the couple you name (typhoid, cholera) will be the worst. dehydration is the biggest killer. Remember to bring water to a boil and then let it cool to destroy pathogens.