vergleiche auch
Siehe auch: Selektionsdruck

A high exciter number, thus a high infection pressure, more probably makes the occurrence of an infection, since per time unit of more exciters can ...
http://www.economy-point.org/i/infection-pres... -

We thus investigated associations between acute infections, infection pressure (i.e. number of daily child contacts) and atopy in one of the largest ...
http://www.ncbi.nlm.nih.gov/pubmed/16650049

I'd only change severe to serious

"pressure" is Quatsch. Eine Krankheit übt keinen Druck aus. "threat" passt bestens!