When was the last time you got fever by stopping smoking?
39 degree Celsius = 102.2 degree Fahrenheit (if the website in which I checked didn't give me a wrong answer or unless I made a mistake). Well, that's in the average range for fever but it's nothing that serious for an adult person. 43 c , however is equal to 109.4 (!!!) f. Alright man, I will be absolutely honest with you. Unless I checked through a rubbish website, I made a calculation mistake, or the Fahrenheit and Celsius scales for weather and human body are different, there is a SERIOUS problem with the thermometer that you have used or you are a super human being because as far as my limited knowledge is concerned, the human body temperature cannot go beyond 107/108 F. Are you sure it was 43 C? I doubt it was!
Ya you will feel like collapsing if at all you get a fever like 109.4 F.
By the way, don't measure the fever immediately after smoking. Don't smoke, eat or drink for at least 20 minutes before measuring the fever. The thermometer might give you a wrong reading if you do otherwise. Also, make sure you are in normal room temperature and you have been in rest for sometimes otherwise you might still get a wrong reading.
Hope that helps!