Salmonella in eggs that been used in mousses and other desserts in their raw state The following text is from the FDA site:


  What is Salmonella? Salmonella, the name of a group of bacteria, is a
  common cause of food poisoning in the United States. Most people
  infected with Salmonella develop diarrhea, fever, abdominal cramps,
  and vomiting 12 to 72 hours after infection. Symptoms usually last 4
  to 7 days and most people get better without treatment. However, in
  some people, the diarrhea may be so severe that they need to be
  hospitalized. In these patients, the Salmonella infection may spread
  from the intestines to the blood stream, and then to other body sites
  and can cause death unless the person is treated quickly with
  antibiotics. Certain people are at greater risk for severe illness and
  include children, older adults, pregnant women, and people with
  weakened immune systems (such as transplant patients and individuals
  with HIV/AIDS, cancer, and diabetes).


Salmonella do really exists sometimes in raw eggs. And lots of chefs, use raw egg whites to make mousse au chocolat, and some chefs uses raw egg yolks to in the mousse or other pastries, where they just beat it with some sugar and add it.

How chefs re-insure that the eggs are salmonella free ?
One alternative is to use pasteurized eggs.