1. They desinfected luggage, clothes etc. with Zyclon B (this was the state of the art measure at that time)
2. They desinfected barracks and mortuaries
3. They built the "Sauna" for the inmates with showers
4. The hair of incoming people was cut off
5. They built crematories because of hygienic reasons. The groundwater level was to high for mass graves.
6. Later they used a microwave desinfection plant for desinfection of luggage and clothes. This was the first plant of this type developed for the concentration camp (the army still used Zyclon B)
The second best way to prevent Typhus are hospitals. And there was a hospital. Not four, but one big hospital (which produces the same result).
Lets go back to the beginning:
"Crematorium IV , by contrast with crematorium II, was designed after Himmler's second visit to Auschwitz in July 1942. Birkenau had become a site for mass murder. All pretense of civility and civilian rules had been shed. The heimat style of Auschwitz I was replaced by the functional vernacular of Birkenau. The architects no longer bothered to draw in autopsy rooms. The space was used for gas chambers." (Dwork & Van Pelt, between 320-21)
You find the answer to this paragraph here: http://vho.org/VffG/2003/3/Mattogno357-365.html
Carlo Mattogno: Die Leichenkeller der Krematorien von Birkenau
im Lichte der Dokumente
This is in German but will be published in English soon (The Revisionist).
Maybe the crema was designed after Himmlers visit. Himmler cared for the hygienic situation (see Mattogno). The alledged mass murder van Pelt is writing about is not proven - and there is a lot of counter evidence. The rest is assumption. Auschwitz I was built in 'heimat style' by the Austrians before the first world war. It was a kuk-barrack. Birkenau never was a barrack. The space was not used for gas chambers as Mattogno proves!