dirty organisms and patients in the hospital are generally in a weakened condition and in positions where they are susceptible to many common infections.
it happens in all health care situations in all countries:
In the United States, it has been estimated that as many as one hospital patient in ten acquires a nosocomial infection, or 2 million patients a year. Estimates of the annual cost range from $4.5 billion to $11 billion and up. Nosocomial infections contributed to 88,000 deaths in the U.S. in 1995. One third of nosocomial infections are considered preventable. Ms. magazine reports that as many as 92 percent of deaths from hospital infections could be prevented.<3> The most common nosocomial infections are of the urinary tract, surgical site and various pneumonias.<4>
In France, prevalence in a sample of hospital patients was 6.7% in 1990, and the rate of nosocomial infections was 7.4% (patients may have several infections).<5> At national level, prevalence among patients in health care facilities was 6.7% in 1996<6>, 5.9% in 2001<7> and 5.0% in 2006.<8>. The rates for nosocomial infections were 7.6% in 1996, 6.4% in 2001 and 5.4% in 2006.
In 2006, the most common infection sites were urinary tract infections (30,3 %), pneumopathy (14,7 %), infections of surgery site (14,2 %). infections of the skin and mucous membrane (10,2 %), other respiratory infections (6,8%) and bacterial infections / blood poisoning (6,4 %).<9>
The rates among adult patients in intensive care were 13,5% in 2004, 14,6% in 2005, 14,1% in 2006 and 14.4% in 2007.<10>
It has been estimated that nosocomial infections make patients stay in the hospital 4-5 additional days. Around 2004-2005, about 9,000 people died each year with a nosocomial infection, of which about 4,200 would have survived without this infection.<11>
In Italy, in the 2000s, about 6.7 % of hospitalized patients were infected, i.e. between 450,000 and 700,000 patients, which caused between 4,500 and 7,000 deaths.<12> A survey in Lombardy gave a rate of 4.9% of patients in 2000.<13>
In UK, they have been estimated as 1/10 in-patients. <14>
In Switzerland, extrapolations assume about 70,000 hospitalised patients are affected by nosocomial infections (between 2 and 14% of hospitalized patients).<15> A national survey gave a rate of 7.2% of patients in 2004.<16>
The rate of nosocomial infections was estimated at 8.5% of patients in Finland in 2005<17>, and 8.2% in England in 2006.<18>
http://en.wikipedia.org/wiki/Nosocomial_infection#Epidemiology