Chapter 19. Microbiology and infection
Routes of infection
Infection can be spread by a number of different routes, these include:
• Droplet spread – the common route of infection for respiratory disease
• Direct contact – hand to wound, mouth to mouth, biting, injection
• Faecal–oral – transmission on the hands from the lower GI tract to the mouth
• Indirect contact – contaminated material or equipment is brought into contact with another casualty.
Terminology
Bacteria
Small, unicellular organisms that have evolved to live in very specialised environments.
Viruses
Much smaller organisms that cannot be seen with a normal light microscope.
Carrier
Someone harbouring a microorganism but not showing evidence of disease.
Source
Area in which a microorganism grows.
Reservoir
The vehicle of transport of infection (e.g. the hands in a faecal–oral transmitted infection).
Incubation period
The time during which the microorganism is multiplying in body tissue before the signs and symptoms of illness have developed.
Infectious period
The time during which the infection may be transmitted to other people.
Important infectious diseases in the UK
Bacterial Infections
Tuberculosis
Organism
• Bacteria of the mycobacterium species.
Symptoms and signs
• Shortness of breath
• Cough
• Discharging skin sinuses in lymph node involvement (rare).
Mode of spread
• Droplet
• Direct spread.
Incubation period
• 4–8 weeks.
Infectious period
• Until treated.
Prehospital precautions
If a patient with active tuberculosis has been transported, the ambulance must be thoroughly aired, linen laundered and contaminated respiratory equipment such as face masks and tubing destroyed. Concerns about staff contracting the disease should be discussed with occupational health.
Notes
The incidence has recently risen in the UK, possibly owing to the increasing number of immigrants, a decrease in the uptake of vaccination and poor living standards in inner cities.
Patients continue to be infectious until their illness has been treated. All paramedic staff should ensure that they are fully immunised against tuberculosis and have a Heaf test (intradermal tuberculin) every 3 years to check their immunity.
Meningitis
Meningitis is an infection of the membranes that surround the brain. When the infection is bacterial and organisms spread to the blood stream, septicaemia is present.
Organism
Bacteria or viruses. The most common bacteria are Haemophilus influenzae, Neisseria meningitidis and Streptococcus pneumoniae.
Symptoms and signs
• Headache
• Photophobia (light hurting the eyes)
• Neck stiffness
• Non-specific flu-like illness
• Bruising rash (non blanching) in associated septicaemia – especially N. meningitidis.
Mode of spread
Droplet.
Incubation period
Incubates for 2–3 days in meningococcal meningitis (due to the bacteria N. meningitides).
Infectious period
Infectious until treated.
Prehospital precautions
When transporting such a patient, a face mask should be worn and the ambulance and all equipment thoroughly cleaned afterwards. Hand washing is essential. If the final diagnosis is proved to be meningococcal meningitis, the occupational health department will consider giving a course of antibiotics to reduce any possible risk of acquiring the infection, although prophylactic antibiotics are not usually given to paramedic or medical staff unless they have been ‘kissing’ contacts (mouth-to-mouth ventilation).
Notes
The child with meningococcal disease may deteriorate very rapidly and must be administered benzyl penicillin and transported to hospital as soon as possible.
Whooping cough
Organism
Bordetella pertussis (bacterium).
Symptoms and signs
• Severe cough, with characteristic inspiratory whooping sound between bouts
• Vomiting
• Weight loss
• Pneumonia.
Mode of spread
Droplet.
Incubation period
Incubates for 7–10 days.
Infectious period
From 7 days after exposure until 21 days after first symptoms.
Prehospital precautions
Whooping cough does not represent a great risk to paramedic staff, but an ambulance should be thoroughly cleaned and aired if a child with the illness has been transported.
Notes
Whooping cough mainly affects children and is most severe in those under 6 months of age. The disease often lasts several months.
Viral infections
Hepatitis A – infectious hepatitis
Organism
Hepatitis A virus.
Symptoms and signs
• General malaise
• Jaundice
• Nausea and vomiting.
Mode of spread
Faecal–oral.
Incubation period
Incubates for 15–40 days.
Prehospital precautions
Universal precautions. Care when handling sharps. Report personal contamination immediately.
Notes
Common in conditions of poor sanitation and tends to occur in outbreaks, for instance in prisons or mental health institutions. The disease tends to run a benign course and usually resolves over a period of 1–2 months.
Hepatitis B – serum hepatitis
Organism
Hepatitis B virus.
Symptoms and signs
• General malaise
• Jaundice
• Nausea and vomiting
• Liver failure.
Mode of spread
• Intravenous (including dirty needles)
• Sexual contact.
Incubation period
Incubates for 40–160 days.
Infectious period
Variable – beware chronic carriers.
Prehospital precautions
Universal precautions. Care when using sharp instruments or needles. Significant contamination with infected or potentially infected blood or body fluids (e.g. needlestick injury) must be reported immediately. The name of the index patient should be recorded for subsequent serological blood testing subject to the patient’s consent. Expert advice should be sought at the earliest opportunity.
Note
An effective vaccine is available for immunisation against hepatitis B. All ambulance staff should ensure that they are vaccinated and have their antibody levels checked every 3 years.
Hepatitis C
Organism
Hepatitis C virus.
Symptoms and signs
• General malaise
• Jaundice
• Nausea and vomiting.
Mode of spread
• Intravenous (including dirty needles)
• Sexual contact.
Incubation period
Incubates for 40–160 days.
Infectious period
Variable – beware chronic carriers.
Prehospital precautions
Care when using sharp instruments or needles. Significant contamination with infected or potentially infected blood or body fluids (e.g. needlestick injury) must be reported immediately. The name of the index patient should be recorded for subsequent serological blood testing subject to the patient’s consent. Expert advice should be sought at the earliest opportunity.
HIV infection and AIDS
Organism
Human immunodeficiency virus 1 or 2 (HIV1 or HIV2).
Symptoms and signs
• Usually secondary to increased susceptibility to infection
• Certain characteristic rashes.
Mode of spread
• Sexual contact
• Intravenous (including dirty needles).
The risk of becoming infected from a needlestick injury is 10 times lower for HIV than for hepatitis B virus, taking equivalent inoculating doses of the virus.
Incubation period
Months to years.
Infectious period
Unknown.
Prehospital precautions
Universal precautions will minimise the infection risk. The ambulance should be thoroughly cleaned and disinfected after use and all disposable items placed in labelled double bags and sent for incineration.
Notes
The chances of acquiring HIV while at work are very small, but disease transmission has occurred in medical and nursing staff through needlestick injury and there are occasional instances of contamination through non-intact skin.
If an accident occurs which puts health service personnel at risk of contracting HIV infection, it is essential that medical advice is sought immediately. Post-exposure prophylactic drug therapy (PEP) is effective in reducing the serum conversion rate from HIV and must be started as soon as possible, ideally within 1 hour.
Herpes virus infections
The herpes viruses cause a variety of different blistering eruptions.
Symptoms and signs
• Herpes simplex type I – cold sores on the mouth, ‘whitlows’ on the fingers
• Herpes simplex type 2 – blistering painful lesions on the genitalia
• Chickenpox virus – diffuse blistering rash, common in children.
Mode of spread
• Sexual contact
• Direct contact.
Incubation period
• Usually 2–10 days
• Chickenpox 14–21 days, remains infectious until the vesicles are dry.
Infectious period
From 2 weeks before rash until vesicles are dry.
Prehospital precautions
Spread of the infection can be prevented by wearing gloves when dealing with such patients and regularly washing the hands.
Chickenpox can affect adults more seriously, so it is best to avoid carrying an infected patient if any member of the crew has not had the illness as a child. Even so, repeat infection can occur.
After carrying such a patient, the ambulance should be cleaned thoroughly to avoid the possibility of spreading the infection to other casualties.
Notes
Chickenpox virus remains dormant in nerve endings and may reactivate at a later date, resulting in ‘shingles.’ This is characterised by vesicles erupting in small areas corresponding to the spinal nerves that supply the skin (dermatomes). It commonly occurs in the elderly, precipitated by stress or underlying disease, and can be very painful.
Pregnant women should not be allowed in contact with chickenpox cases.
It is possible in the non-immune to contract chicken pox from active shingles.
Influenza
Organism
Influenza RNA viruses (multiple serotypes).
Symptoms and signs
• Pyrexia
• Aches and pains
• Cough.
Mode of spread
• Air-borne droplet spread
• Contact with contaminated surfaces.
Incubation period
Incubates for 2–4 days.
Infectious period
Infectious for 4–5 days following onset of symptoms.
Prehospital precautions
Simple precautions required: use gloves and masks and wash hands after treating suspected cases. Front-line care workers should receive annual vaccination against seasonal influenza strains.
Notes
Unusual serotypes such as H1N1 ‘swine-flu’ have the potential to cause serious epidemics in non-immune populations.
Other childhood infectious diseases
Measles
Organism
Measles virus.
Symptoms and signs
• Rash
• Fever
• Cough
• Conjunctivitis.
Mode of spread
Droplet.
Incubation period
Incubates for 10 days.
Infectious period
From beginning of symptoms until 4 days after appearance of rash.
Prehospital precautions
Patients with measles do not present any particular risk to paramedic staff, but the ambulance and equipment should be thoroughly cleaned after use to prevent transmission of infection to others.
Notes
Measles is infectious from the beginning of symptoms until 4 days after the appearance of the rash. The illness is not always benign and can result in deafness and brain damage.
German measles (rubella)
Organism
Rubella virus.
Symptoms and signs
• Transient rash
• Lymphadenopathy.
Mode of spread
Droplet.
Incubation period
Incubates for 14–21 days.
Infectious period
From 7 days before until 4 days after the rash.
Prehospital precautions
All female ambulance staff should ensure that they are immunised against the disease and if pregnant, should not transport patients who are suspected of having the disease.
Notes
The most important aspect of rubella infection is the potential fetal damage, which can result when mothers are exposed to the virus in the early months of their pregnancy. For this reason, all British girls are immunised against rubella prior to leaving school.
Mumps
Organism
Mumps virus.
Symptoms and signs
• Swelling of the parotid glands
• General malaise
• Orchitis (testicular inflammation) and sterility after infection in adulthood.
Mode of spread
Droplet.
Incubation period
• 14–21 days
• The patient is infectious for several days before the parotid gland swells and for the subsequent 5 days.
Infectious period
From 2 days before parotid swelling until 5 days after.
Prehospital precautions
Adult males who have not had mumps should avoid transporting children who are suspected of having the illness.
Notes
Inflammation of the ovaries (oophoritis), thyroid (thyroiditis), brain (encephalitis) and pancreas (pancreatitis) can all result from mumps infection.
Minimising the spread of infectious diseases
The risk of catching an infectious disease is small and can be minimised further by the observation of some simple precautions.
Immunisation
Paramedical staff should ensure that their immunisation schedules are up-to-date.
General hygiene
• Hands should be thoroughly washed after each patient
• Nails must be kept clean and regularly trimmed otherwise they may act as a reservoir for bacteria
• Hair should be kept short or tied back so that it cannot contaminate a wound
• A paramedic with any large wound or open weeping areas should not work until the injury has healed. Small lacerations should be cleaned and dressed with a waterproof dressing to decrease the risk of infection.
Equipment
Whenever possible, disposable equipment should be used and then replaced.
Disposable sharps should be kept in puncture-resistant containers.
Other disposables should be placed in plastic bags and clearly marked before being sent to be destroyed.
The ambulance should be aired regularly and the interior cleaned thoroughly at least once a day.
All non-disposable equipment should be scrubbed with an antiseptic solution after each patient and linen should be changed and sent for cleaning to the laundry.
Immunisation requirements for ambulance service staff
• Tetanus – a booster should be given every 10 years
• Tuberculosis – a Heaf test is necessary every 3 years to check on immunity
• Hepatitis B – a full course of three injections should be given and then antibody levels checked. If levels are low a further booster dose may be necessary. Antibody levels should be checked every 3 years
• Rubella – antibody titres should be checked and immunisation offered to female personnel who are not immune.
Measures to avoid the spread of infectious disease
• Ensuring that one is fully immunised
• Observing good general hygiene
• Using disposable equipment when possible
• Having a regular cleaning schedule for equipment and the ambulance
• Using ‘universal precautions’ (see below)
• Taking extreme care when using sharps.
Universal precautions
• Ensure that protective equipment is always available in the ambulance
• Observe blood and body fluid precautions with ALL casualties
• Wear gloves whenever exposed to blood or other body fluids
• Protect eyes, face and trunk if blood is likely to be splashed
• Wash immediately if blood or body fluid is splashed onto skin.
Sharps Safety
• Extreme care should be taken when using needles, blades and other sharps
• Sharps should be disposed of immediately in a puncture-resistant container
• Needles should never be re-sheathed or broken because of the risk of needlestick injury
• Sharps should not be handed from one person to another
• Beware of sharp items such as broken glass or edges of metal.
High-risk situations
There are several situations in which ambulance staff may be subjected to a higher risk of exposure to an infectious disease. In these situations further precautionary measures may be necessary.
Cardiopulmonary resuscitation
There have been no case reports of HIV or hepatitis B infection caused by transmission of the virus during mouth-to-mouth ventilation. However, both viruses are present in saliva so a small risk may be present. In addition, there have been isolated cases of transmission of herpes virus, tuberculosis and meningitis. For these reasons mouth-to-mouth ventilation should be avoided if at all possible. Instead, ventilation should be performed using a Laerdal pocket mask with a one-way valve or a self-inflating bag with mask.
Transport of high-risk patients
On some occasions an ambulance may be called upon to transport a patient with a known infectious disease. In this case some anticipatory measures can be taken. A crew with known immunity to the disease should be selected where possible (e.g. mumps). Disposable linen should be used in the ambulance, and gowns and masks should be worn by the crew whenever they examine the patient. After the transfer of the patient all disposables should be placed in plastic bags and sent for incineration.
Action to take in case of exposure to infectious disease
Crew members who have been exposed to an infectious disease and are worried that they may have contracted the infection should contact their occupational health department.
Needlestick injury
• After a needlestick injury, immediately wash the area of the injury in running water
• Ask the patient if he is known to have an infectious disease
• If the patient gives consent take a blood sample to assess hepatitis and HIV status ( the patient will need counselling before having these investigations)
• Attend the occupational health unit or local Emergency Department without delay
• Ensure blood is taken for checking hepatitis serology and to ensure immunity.
Any treatment will be based on a risk assessment depending on one’s own (or likely) hepatitis status and that of the patient. The occupational health department may offer HIV counselling.
Infections transmitted from paramedic staff to patient
All paramedic personnel have a duty to ensure that they are healthy and are not harbouring any potentially infectious diseases. Any concerns about illness should be discussed with the occupational health department. Paramedics should not work if they have large open wounds and must ensure that any small cuts or abrasions are covered with waterproof dressings.
For further information, see Ch. 19 in Emergency Care: A Textbook for Paramedics.
