Are bacteria in the blood contagious?
In order to clarify this question, it is first of all important to remember that an infection is the active or passive transmission of a pathogen into another organism, such as the human body. If the pathogen remains in this organism and can then multiply, a so-called infection occurs, which can be followed by the development of the corresponding associated clinical picture. The presence of a risk of infection when dealing with sick fellow human beings is not equally pronounced in every illness and in every stage of the illness, but depends above all on the excretion of active pathogens by the patient.
In principle, every sick person who excretes “viable” pathogens is potentially contagious, regardless of his or her clinical picture. The transmission of infectious pathogens is usually possible through contact with body fluids and the excretions of the sick person. An example of this is the spread of the cold viruses via the secretions of the nasal and pharyngeal mucous membranes that are formed in connection with the cold and are expelled via sneezing and coughing.
The transmission and subsequent infection is possible through direct contact with the sick person, but also through indirect contact with the body secretions of the affected person, for example through door handles. Other examples of diseases in which the patient’s excretions are particularly infectious are most stomach or intestinal diseases associated with vomiting or diarrhoea. Diseases, such as HIV, are particularly associated with the detection of the pathogens in the blood.
In the case of these, contact with the patient’s blood must be regarded as contagious, whereby transmission via uninjured skin is very unlikely. The situation is similar with most pathogens that are detectable mainly in the blood. Accordingly, a person who has a positive result in the detection of active bacteria in the blood is in principle infectious and there is a risk for others to become infected with them.
However, it should be noted that the transmission of these pathogens is normally only possible through contact with body fluids, especially the blood of the person concerned. However, patients in whom the bacteria have indirectly entered the bloodstream via colonisation and infection of tissue and subsequent transfer to the blood usually have a greater risk of infection, as in these patients the infection with the pathogens can originate not only from the blood but also from the primarily colonised tissue. Let us return to the above-mentioned example of pneumonia: in this case, infection with the pathogens of this patient would originate not only from the blood, but also from the bronchial and pharyngeal secretions formed in the course of his lung disease, which he usually expels through a severe cough.
