Can a mild infection give you the shakes?

A rigor, the symptom which you experienced, can indeed be alarming. But be reassured: as your GP explained, it is only a bout of exaggerated shivering that occurs when you have a high temperature and is a marker for what may be a significant infection.

When an infection takes hold, the inflammation causes various chemicals to be released into the bloodstream. These alter the setting of the natural thermostat in the brain, causing you to feel cold.

The body tries to remedy this drop in temperature by shivering — an involuntary muscle reflex that causes a rise in body heat.

When diagnosing the cause of rigors, doctors look for evidence of an infection — for instance, a respiratory infection, which would also cause a sore throat or cough; or a urinary infection, bladder pain or burning when passing water.

Abdominal symptoms, such as pain, vomiting or an upset bowel may also signal an infection in the colon, such as diverticulitis.

If nothing is immediately apparent, as was the case with you, reaching a conclusion about the cause is more difficult.

Here, the patient’s medical history is important and we need to consider a range of factors, such as past surgery or rheumatic heart disease (when the lining of the heart or the heart valves is damaged by a streptococcal throat infection earlier in life and has now become a source of infection).

Foreign travel and even contact with animals, may be other factors linked to infection. However, it is quite common to come across patients in whom there is no definite reason for the rigor — and, in a man of your age, the urinary tract is often to blame, even without any specific bladder symptoms.

One possible explanation is the gradual enlargement of the prostate in older men that occurs naturally with age. The prostate gland wraps around the exit pipe from the bladder and any increase in its size hinders the flow of liquid. As a result, there is usually a greater volume of residual urine remaining in the bladder after visiting the loo.

This residual liquid is not noticed by the individual, but the bacteria it contains can multiply and cause infection. The first clue of this might be a rising temperature and rigors — even without any other symptoms.

For that reason, even if an initial clinical examination of the throat, chest and abdomen does not reveal the source of infection, a dipstick test of the urine is essential to confirm or exclude that type of infection.

If testing of the urine shows a normal result and the temperature and rigors continue, then more exhaustive investigation is called for, such as blood tests and examination of the heart, lungs and abdomen by imaging with ultrasound or CT scanning, which may reveal an infection or abscess somewhere else in the body.

This time, the antibiotics you took were effective, despite the lack of an exact diagnosis. But if there is another episode, you should be investigated in further detail.

Wild, Wild West

The boys are zapped back in time, and Dean (wearing a serape) couldn't be happier because he's obsessed with Clint Eastwood movies. At first he loves the authenticity (like Sam stepping in horse poop), but Dean quickly realizes that everything isn't like he thought. Nobody likes his outfit, the whiskey tastes like gasoline and the saloon girls are covered in cold sores.

They also watch as a man is hanged in the town square, but when that same victim goes around killing people by reducing them to ash, the boys learn that he's the phoenix. I'm kind of upset that the phoenix is just a person, like the dragons. Why can't phoenixes and dragons be awesome, mythical creatures?

Still, Dean fights the phoenix while Sam goes to meet Samuel Colt and get his gun. Colt is a surly old retired hunter who wants nothing to do with the life anymore. However, he's clearly been at this a while, because he has absolutely no problem believing that Sam is from the future. Sam gets the Colt, hurries back and gives it to Dean, who then has the shootout from the start of the episode with the phoenix. And Dean proves that he's the fastest draw in the old west, killing the phoenix and reducing it to ashes.

Castiel's Dirty Little Secret

In the present, Rachel summons Cas to an empty warehouse to talk about how she doesn't approve of his methods to fight the war against Raphael and that she knows his "dirty little secret." She then tries to stab him with an angel dagger, but he fights back and gets the upper hand, killing her. That's right, after two short scenes, the big new angel character Rachel is killed.

But it begs a bigger question: what is the dirty little secret? Was she talking about how he had Balthazar unsink the Titanic to get 50,000 new souls, or is Cas doing worse things to win his war? I'm starting to think that he's been doing some very bad things and, as much as I love Cas, I suspect he might even be the big bad of the season and helped get the Mother of All free to help him fight Raphael. I hope I'm wrong, but Castiel is definitely not behaving like a good angel this season.

Deus Fed-Ex Machina

Injured, Cas can't bring the boys back without powering up, and that involves touching Bobby's soul. I'm starting to think Bobby's soul is the most valuable thing in the world given how much it's come into play in the past year. He does and brings the boys back, right before they got the phoenix ashes. So it was all for nothing.

Or was it? Just like at the end of Back to the Future 2, a delivery man shows up at that exact moment with a package for Sam Winchester they've been holding onto forever without explicit instructions to deliver at that specific moment. Inside Sam finds his old phone he left with Samuel Colt, a note from Colt, and, most importantly, the ashes of a phoenix. It might be a little too convenient, like when Supernatural super fan Becky told them where the Colt was after reading it in the books at the end of "The Real Ghostbusters," but since it's just a rip-off of Back to the Future, I'll allow it.