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Do rigors indicate serious bacterial infection?


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We often see children with pyrexia and have to decide on whether or not they have a serious underlying bacterial infection.  When the parent describes, or uses the word ‘rigors’ we all get a bit twitchy ourselves.  But is there any evidence to suggest that rigors = serious bacterial infection?


Some more background…

A chill is ‘a sensation of cold occurring in most fevers’.

A rigor is ‘a profound chill with pilo-erection associated with teeth chattering and severe shivering’.

There is general consensus that rigors indicate a rapid rise in temperature, but nobody seems to know whether it indicates bacteraemia.


What were the search terms?

Using PubMed, a search was run using

rigors OR rigor OR shaking


bacteraemia OR bacteremia OR sepsis OR septicaemia OR septicemia


How many studies have been carried out?

Unfortunately there is only one study on this topic – Tal et al (1997)

Lumsden and Potier reviewed this question for Emergency Medicine Journal in 2007 and also found only one result.  There have been no new studies since then.


Ok, well I guess one will have to do.  Who did they look at?

This was a prospective study which included:

100 patients who had a pyrexial illness (>38.5 degrees) along with rigors (febrile seizures were excluded)

334 patient who were matched in age, sex, temperature and clinical state but with NO rigors


What investigations did these patients have?

All patients had bloods (FBC, ESR, blood cultures); urine analysis and culture; and CXR.  Some had lumbar punctures.


What was the outcome measured?

The outcome was presumed or proven bacterial infections.

Proven was from blood, urine or stool culture.

Presumed was from clinical assessment and CXR (the authors acknowledge that some of these may have been viral).


What were the results?

There were significantly greater positive blood cultures in patients with rigors (15%) compared to those without rigors (6%).  This was more significant in those over 1 year old (p<0.015).

The most common pathogen was Strep pneumoniae.

In the presumed bacterial group, more patients had rigors.  This was statistically signifianct (p<0.005)


How do we know what a rigor is?

Well, the short answer is….we don’t.

This study relied on parental reporting (60%)  or health professional witnessing (40%).

There is nothing that clarifies the difference between a shiver and rigor so it does make selection a bit tricky.


Will/should this study change my practice?

It’s difficult to know what to take from this.

The recruitment of group is questionable as we really don’t know how accurate the assessment of having a rigor was (although that’s the same in actual practice).

That the outcomes include ‘presumed bacterial infection’ means that we don’t actually know whether or not there was a true bacterial infection in the ‘presumed bacterial group’.  So the result that more patients in the presumed bacterial group had rigors is self-fulfilling and therefore not helpful to our practice.

Therefore, the useful outcome is that there was a significant different in positive blood cultures between the rigors and non-rigors group.

It is a small study and the definitions are sketchy, but it is something to go on.


I’m still confused – what’s the conclusion?

There has only been one study looking into whether rigors indicate an underlying bacterial infection.  This study does show that more patients with rigors have a positive blood culture.

But the study was small, with definitional problems that have a huge impact on its usefulness.

Not one to hang your hat on, but bear it in mind when you see a patient with rigors.



Isselbacher KJ. Harrison’s principles of internal medicine, 13th ed. McGraw-Hill Inc. 1994, p83.

Lumsden D, Potier, K. Rigors in febrile children may be associated with a higher incidence of serious bacterial infection. Emerg. Med. J. 2007;24(9): 663.

Tal Y, Even L, Kugelman A, Hardo€ D, Srugo I, Ja€e M. The clinical significance of rigors in febrile children. Eur. J. Pediatr.. 1997;156:457-459.

About the authors

  • Tessa Davis is a Consultant in Paediatric Emergency Medicine at the Royal London Hospital and a Senior Lecturer at Queen Mary University of London.


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14 thoughts on “Do rigors indicate serious bacterial infection?”

  1. I had 2 episodes of rigors, about 15-20 minutes each. The first was at the onset of sepsis, I had a pulse rate of about 145, blood pressure of about 90/50 and shortly after the first rigors my temperature went to 101F. The second episode was the following morning while I was in the ER after being placed on broad spectrum antibiotics as a precautionary measure the previous night. The second episode convinced the ER that I had something more than prostatitus. Later, the infectious disease doctor said the rigors was the result of a bacterial shower, and the sepsis was an ESBL e-coli.

  2. I have had seen this twice with two different men at different times. First man was subsequently diagnosed with.blocked bile duct and second with acute appendicitis just recently. In both cases emergency surgery followed.
    I called an ambulance on both occasions and was glad I did.

  3. Hi

    I can’t believe there is someone else with exactly the same symptoms as me. I have never had any success with any doctors, tests, etc but anti biopics work! If you have a rigors, take anti biopics for 2 weeks, they will stop after a few days. They may return months later but it really takes the pressure off for a while.

  4. Hello all.  I too experience these rigors and have for many years now. I’ve spoken with multiple doctors and none of them have offered any reason or solution. I’ve researched this on my own (which has proven to be very difficult, as I can’t seem to find much information).

    I did read about something called “cold urticaria” that matches my symptoms. From what I gather, it is an allergy to cold essentially. I’m not sure if that’s what this but it’s the closest I’ve seen so far.

    My symptoms range in severity and I don’t know why or what makes them worse. This evening I was asleep and woke up to get a glass of water from fridge. The minute I touched the cold glass I felt freezing, started shivering uncontrollably, and then a flush of heat radiates through my body. I now have been through this enough and know that I need to cover up all exposed skin and try to bundle up asap to stop symptoms from getting worse.

    My most servere episode was in public last year. I was leaving a store and it was cold outside. The minute I stepped outside it started (I literally ran to my car to turn on heat bc I knew what was happening) …freezing cold feeling, uncontrollable shivering, teeth chattering, muscles locking up, red welts on my skin, then flush of heat through entire body, itchy skin, hard to swallow and the weirdest symptom when it gets really bad – metallic taste in my mouth! I also notice that when I have an episode, the following 48 hours seem to make me very susceptible to having more episodes and I have to be very careful to not get chilled again. Could it be my body releasing histamine to fight an allergy (cold) and these are the symptoms?? 

    Sorry for the long post. Hoping someone will see this and can shed some light on what’s going on. 

    1. You have a twin in Utah who experiences the SAME thing! I thought I was just a wimpy girl who couldn’t tolerate a chill. You explain it quite eloquently!

  5. I had rigors with pnemonia, pneumonia bacterium and sepsis. I would describe them as severe chills and shaking that can be seen and creates a sense of immediate need for medical intervention by others. I was in the hospital and at the beginning of IV treatment for sepsis. My hospital treatment was excellent and I was home in four days.

  6. I have lived with rigors my entire life. I am a 36 year old male and lead a very active and healthy lifestyle. I can only describe these episodes as an extremely painful, full body muscle contraction, accompanied by chills and chattering teeth.
    I never know when they are going to happen, and I experience them at least every month or so. There is no obvious cause for them. But I can tell they are about to come on and it is when I experience a change in temperature from warm to cool. It can be something as simple as getting out of my chair to go to the restroom. Also, sudden movements after a temperature change activate them. For me, they always happen after sundown. I have never experienced them during the day.
    I’ve searched everywhere, with no answers to this problem, which is debilitating when it strikes as I am down for the night. I just wanted to throw in my info.

    1. Nathan, have you found any answers about your condition? The symptoms you describe are exactly what I experience, just a few times per year. What I also would like to add is the dark psychological state I fall into during these rigors . . . similar to a panic attack. I don’t know which is the cause, or effect. They always seem to happen when I wake up in the middle of the night cold, or when getting into a bathtub. My doctor doesn’t seem too concerned, and attributes it to an infection or UTI. But I never have any adverse effects the day before, or the day after, except being tired due to the lack of sleep.

  7. I am aregistered nurse and also have experienced rigors, the latest episode 2 nights ago. I also suffer from GERD wich seems to precipitate the fever and rigors. Following tylenol my rigors stopped but my fever was still about 38.8 degrees . I have one to 2 episodes a week. My physician has not investigated and doesnt subscribe to the notion of aspirational pneumonia from GERD. Rigors are prolonged and uncontrollable shivering for me. My back arches uncontrollably. This is short lived ie back to normal the next day . Food for thought, no pun intended.

  8. Manuel Datiles III, MD

    I personally experienced rigors while being confined for small bowel and urinary obstruction in April 2016. I am an ophthalmologist and researcher (tenured Senior Investigator) at the NIH in Bethesda MD as well as an adjunct associate Professor at the Johns Hopkins University School of Medicine in Baltimore. I was being treated with NPO diet, IV fluids, a naso-gastric tube and a urinary catheter, and was an in-patient at the Shady Grove Adventist Hospital in Rockville, MD.
    In the morning of April 28, 2016, after brushing my teeth (may have dislodged some plaque into my blood stream?) I developed severe chills and shaking accompanied by high fever (41 degrees celsius) and eventually became tired of the severe chills and shaking with heavy breathing after 10 minutes. My daughter and the staff nurse piled blankets and my overcoat on top of me and took my BP which was 180/100, pulse 120, with temp of 41. I asked for oxygen and the head nurse came and started oxygen and said I had rigors! I asked her to call the Hospitalist on call and ask for help. He immediately prescribed acetaminophen IV and a few seconds after getting the IV dose, my rigors symptoms immediately lessened. After 5-6 minutes the rigors were gone and I felt completely well again with no sequelae, except since I happened to be on cardiac monitoring, the cardiologist was freaking out due to atrial fibs, which disappeared after the rigors stopped. Later I underwent a nuclear stress test (chemical) that showed a very small mild demand ischemia in the cardiac apex which disappeared at rest and she also said rule out possible artifact.
    I don’t know where the rigors came from but it also disappeared as quickly as it came!

    1. Thanks. I can only see the abstract in the article you mention, but it looks like it uses rigors in combination with other criteria rather than as an indicator alone.

      I think you’re right it’s more a word some people use to voice their gut feeling.

      But often people get bogged down in the ‘was he just shivering or was it a RIGOR?’ conversation.

      It’s usually the parents describing it in the history, and actually it’s not really a strong indicator of anything.

  9. Hard to interpret this study since we now vaccinate against a number of S.pneumo serotypes.

    If we repeated the study now would we get the same results?? My gut feeling is that we would see no difference, but I have no scientific data to back this up!

    1. Good point. Essentially, even though we speak about rigors meaning something significant with regards to the seriousness of infection, there isn’t actually evidence to back this up.



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