HC26: Prevention and control

Preventive measures

There are many ways a source can infect a host, which means there also are many preventive measures:

• Reservoir
  • Elimination: everything that can be done to eliminate a microorganism
    • Cleaning
    • Disinfection
    • Sterilization
    • Pasteurization
    • Water purification
    • Sewage treatment
    • Adequate heating of food
    • Screening of blood products
    • Social development
• Source
  • Elimination
    • Cleaning
    • Disinfection
    • Sterilization
    • Pasteurization
    • Water purification
    • Sewage treatment
    • Adequate heating of food
    • Screening of blood products
    • Social development
  • Source isolation
• Transmission
  • Interruption of transmission
    • Hand hygiene
    • Vector control
    • Asepsis
    • Use of gloves, gowns and face masks
    • Protection against insect bites
    • Safe handling of sharps
    • Safe sex
• Host
  • Protective isolation
  • Protection of the host
    • Vaccination
    • Passive immunization
    • Antimicrobial prophylaxis
    • Social development

Outbreaks

Whether something is called an outbreak depends on how often a certain disease normally occurs. If a disease usually rarely occurs, but suddenly the prevalence rises, there is an outbreak.

Q-fever

Clinical presentation:

A while ago there was an outbreak of Q-fever. Q-fever is caused by coxiella burnetti, an intracellular bacterium which lacks a cell wall. The clinical presentation of Q-fever is:

• Fever, headache
• Sometimes:
  • Coughing
  • Pleural pain
• Rarely:
  • Granulomatous hepatitis
  • Chronic Q-fever: endocarditis, infections of vascular prostheses of prosthetic valves

Q-fever is mainly diagnosed based on antibodies in the serum → aren't visible with microscopy.

Infection chain:

The infection chain of Q-fever consists of:

• Reservoir: very complex → zoonosis mainly started by ticks
• Source: animal products or animal abortions
  • Especially from goats and sheep
  • Abortion products form spores that can survive for years
• Transmission: inhalation
  • Transmission from host to source is very unlikely → humans are final stadium hosts
• Host: humans

The only way to fight Q-fever is to destroy the reservoir → all involved animals have to be killed. Subsequently, all sheep and goats need to be vaccinated.

Hospitals

Hospitals take many measures to prevent and control infections. There is a high risk of nosocomial infections such as:

• Postoperative wound infection
• Catheter-related bloodstream infections
• Urinary tract infection
• Hospital acquired pneumonia

Prevention and control of these infections mainly consists of hand hygiene and isolation.

Hand hygiene:

Ignaz Semmelweis (1815-1865) worked in 2 different wards of the General Hospital of Vienna in the 1840's:

• Ward 1: doctors and medical students
• Ward 2: midwives

In ward 1, there was much more maternal mortality caused by fever than in ward 2. Semmelweis noticed that the doctors and students didn't wash their hands with chlorine solution, while the midwives did. In ward 1, microorganisms from corpses were transmitted to the next mothers causing them to die.

The hands can transmit resident and transient microorganisms. Resident microorganisms reside in cracks in the skin and transient microorganisms on the surface → after handwashing, only the transient microorganisms disappear. After using soap, the resident microorganisms come out of the cracks but don't disappear → it seems as if there suddenly are more microorganisms.

The WHO campaigns for 5 moments of hand hygiene:

1. Before patient contact
2. Before aseptic task
3. After body fluid exposure risk
4. After patient contact
5. After contact with patient surroundings

Dress code:

In the hospitals, watches and jewelry like rings and bracelets aren't allowed. It is allowed to wear rings on a necklace and small earrings. Long hair has to be tied, the doctor’s jacket has to be closed, nails cannot be polished and long sleeves are forbidden.

Isolation measures:

There are 2 types of isolation measures, which depend on how the transmission goes from the source to the host:

• Source isolation
  • Contact isolation
    • The patient is in a room with open doors
    • Gloves need to be worn while treating the patient
    • Alcoholic hand gel needs to be used after removing the gloves
    • Microorganisms that can only be transmitted by contact
      • For instance in cases of giardia lamblia
  • Droplet isolation
    • The patient is in a room with open doors
      • Droplets cannot travel further than 1 meter
    • A mask is used
    • Often used during virus infections
      • For instance in cases of influenza A virus

• In this case contact isolation is also necessary
  • Aerogenic isolation
    • The patient is in an isolation room
      • There are locks which refresh the air between the room and the corridor
    • An FFP2-mask is used
    • For instance in cases of mycobacterium tuberculosis and varicella zoster
  • Strict isolation
    • Contact + aerogenic isolation
    • Everything is necessary
      • Gown + surgeon mask
    • For instance in cases of:
      • MRSA
      • Influenza pneumonia
      • Chickenpox and measles
      • Tuberculosis
      • Viral hemorrhagic fever
      • SARS
• Protective isolation
  • Alcoholic hand gel
  • Face mask
  • Protection jacket

In case of severe infectious diseases, like viral hemorrhagic fever, extensive measures need to be taken. Special protective equipment needs to be used, which cannot be worn for longer than 1 hour.

Antibiotic prophylaxis

Antibiotic prophylaxis is a form of primary prevention. It can be used when a patient has a defined increased risk of infection → prevention is better than timely diagnosis and treatment. It is an antimicrobial agent aimed at microorganisms likely to cause infection. It should only be used as short as exposure is likely. Indications to use antibiotic prophylaxis are:

• Asplenia
• Granulocytopenia
• Hypogammaglobulinemia
• Complement deficiency