8- Health, safety and you Flashcards
What are the transmission routes
- Soil – worms/some bacteria - eg Ascaris lumbricoides; Cl. tetani
- Animals/insects – e.g. Pneumocystis jirovecii; rabies virus; Plasmodium spp. (malaria)
- Food/water – e.g. Enterobacteria; hepatitis A virus; vCJD
- Faecal-oral – e.g. Enterobacteria; hepatitis A; noroviruses
- Aerosol – e.g. B.pertussis (whooping cough); measles & influenza viruses
- Direct contact – e.g. sexual; e.g. HIV infection; some herpesviruses
- Transplacental – e.g. rubella virus; Zika virus
- Iatrogenic – e.g. blood; hepatitis B and C; HIV
What is the parenteral route
Entry into the body by injection is known as the parenteral route of inoculation, and distinguishes this route of entry from all other routes e.g. oral or via a wound
What non human sources cause transmission
Animals – Rabies dogs
‘Rabies is a vaccine-preventable viral disease which occurs in more than 150 countries and territories
Dogs are the main source of human rabies deaths, contributing up to 99% of all rabies transmissions to humans. Infection causes tens of thousands of deaths every year, mainly in Asia and Africa
* Rabies elimination is feasible through vaccination of dogs and prevention of dog bites.
Who gets rabies
- 40% of people bitten by suspect rabid animals are children under 15 years of age
Immediate treatment of rabies
- Immediate, thorough wound washing with soap and water after contact with a suspect rabid animal is crucial and can save lives’.
How is rabies transmission between humans
Transmission of micro-organisms in a healthcare setting can be:
1. Through cross-infection (patient to patient), either directly or indirectly
2. from patient to healthcare worker
3. from healthcare worker to patient
Further types of transmission
PERCUTANEOUS – injuries through needles and other sharps, human bites and human scratches.
MUCOCUTANEOUS – exposures to the mucous membranes of the eyes and mouth.
Which contaminated sources cause transmission
- Mucosal secretions and saliva
- Fluids from vesicles or other open lesions
- Faeces, vomit and urine
- Fomites
- Pus
- Blood
Fomites are objects or things e.g. a cup or the surface of a table or a bedsheet.
Nosocomial infections are infections occurring in hospitals.
What are the preventative measures against rabies
Handwashing and good general hygienic procedures
2. Use of appropriate protective clothing
3. Appropriate and effective sterilisation of instruments and disposal
4. Education and awareness – Infection control measures, Patient isolation
5. Immunisation, where available
What is HIV- the virus
A microorganism in a healthcare setting
How does HIV spread
……or….. ……. have to broken for it to infect
Spread from contaminated needles, blood or blood-products, the main problem for hospitals
Virus has been isolated from human blood, semen, vaginal secretions, saliva, tears and breast milk. Commonest routes of transmission are via blood, semen and vaginal secretions
Contact with saliva is not a route of infection, and there is no evidence for transmission by an airborne route or via food, water, fomites or insects
Skin or mucous membranes must be broken for HIV-1 to infect
What are the risks of HIV transmission
- Blood transfusions – 3-5% of all infections
- Intravenous drug abuse – 5-10% of all infections
- Sexual intercourse – 80% of all infections
(Risk of transmission is higher to the passive {receptive} partner) - Perinatal infection – 10% of all infections (From mother to baby)
(via transplacental, intrapartum, blood, genital secretions, breast milk)
Stages of HIV replication
- Attachment to host cell receptor. Viral core with single stranded RNA and reverse transcriptase (RT) enzyme released into the host cell cytoplasm.
- RT enzyme converts viral ssRNA into viral double stranded DNA, which enters host cell nucleus and incorporated into the host cell genome with help of enzyme called integrase.
- Integrated viral dsDNA (termed ‘provirus’) remains latent in host cell genome until cell is activated by a foreign protein.
- Following activation of the cell, dsDNA of provirus is transcribed into viral ssRNA. This migrates into host cell cytoplasm.
- Viral ssRNA replicates itself to form progeny ssRNA and also acts as a viral protein template.
- Progeny viral ssRNA and viral core proteins assemble to form progeny viral cores.
- Progeny viral envelope protein is inserted into host cell membrane.
- Newly formed viral particles released to exterior of cell by budding.
What is the natural history of HIV
- HIV is a chronic infection with ongoing viral replication
- Progressive decline in T-lymphocyte count. Below 200 cells/ml, the individual is defined as having Acquired Immunodeficiency Syndrome (AIDS), and is at risk of opportunistic infections
- On average it takes 10 years to progress to AIDS in an untreated person but there is wide individual variation
- The major determinant of the rate of progression to AIDS is the amount of HIV virus particles in the bloodstream
What is pathogenesis
- Acute infection with spread to lymphoid tissue
- Virus present in helper T lymphocytes and macrophages in both a latent (hidden) and a replicative form
- Control of the infection by the immune defences, particularly via cytotoxic T lymphocytes.
- Loss of immune control with time, virus escape by genetic variability
- Loss of greater numbers of helper T lymphocytes through virus and host cell destruction
- Development of AIDS and the appearance of opportunist infections
What are the opportunistic infections in AID
- Bacterial skin infections
Folliculitis (both caused by Staphylococcus pyogenes) - Fungal skin infections
Candidiasis - Viral skin infections
Zoster/Shingles
Herpes simplex virus
Warts
What are the procedures following accidental exposure
- The nature and extent of the exposure is assessed immediately by an informed clinician
- Treatment with appropriate anti-HIV drugs should be commenced immediately
- Usually a combination of drugs is used, including reverse transcriptase inhibitors and protease inhibitors
What causes liver inflammation
- HAV – Primarily through faecal-oral (Usually resolves on its own)
- HBV – Blood and bodily fluids (Lead to chronic hepatitis, liver cirrhosis and cancer Lead to HDV a defective virus that needs HBV to replicate)
- HCV – The same as HBV
What is hepatitis B (HBV) and classification
Long incubation period and there is some antigenic variation, carrier state DNA
Classification- hepadnavirus
What is hepatitis C (HCV) and classification
Long incubation period, much antigenic variation, carrier state, RNA
Hepatitis A (HAV) and classification
Short incubation period, little antigenic variation, no carrier state, RNA
Classification- enterovirus
Who are the risk groups for hep B and C
- Drug addicts (declining due to available vaccine for Hep B)
- Individuals with lympho-proliferative disorders
- Individuals on immune suppressive therapy
- Users of blood or blood products on a regular basis
- Individuals in ‘at risk’ occupations
Symptoms of hepatitis B and C (blood borne)
- Nausea
- Jaundice
- Enlarged liver (hepatomegaly) + fibrotic (Due to continuous inflammation)
- Enlarged spleen (splenomegaly)
- Slightly raised temperature
- Pale stools
- Blood in urine (hematuria)
What is the pathogenesis of HBV
- Transmission
- Acute infection – can range in severity (HBV surface antigen in the blood)
- Chronic infection – When virus persists for more than 6 months (HBsAG and HBV core antigen)
Carrier state – Some people with chronic HBV may enter a carrier state, with no symptoms.
What is HCV (Hep C virus)
- There are 6 HCV genotypes and about 80 subtypes within the six genotypes
Acute HCV infection is often asymptomatic Chronic infection (Causing no symptoms/ liver issues) - HCV persists in 70-80% of infections
- Diagnosis and screening is by an ELISA test for viral antibody, but HCV infection is difficult to recognise in its early stages
What controls hepatitis B
Screening of blood and blood products
Hygienic measures (contaminated needles, tattoos, sexual contact)
Vaccination against HBV – the subunit HBsAg preparation
What controls hepatitis C
Screening of blood and blood products
Hygienic measures (contaminated needles, tattoos, sexual contact)
No vaccine against HCV yet available! Antiviral medication given
What controls hepatitis A
Hygienic measures (faecal-oral spread)
Common vehicle outbreaks (contaminated water/food)
Inactivated, whole virus vaccine
What is a notrovirus
from infected faeces or vomit
What is ebola virus
(from all infected body fluids)
* Ebola is a severe haemorrhagic disease caused by negative sense ssRNA viruses
* Infection of humans is probably via fruit bats. In some ‘at risk’ countries the sale of fruit bats for culinary purposes is now banned
* All bodily fluids are infectious; full body protective clothing must be worn by medical and ancillary staff dealing with patients and samples
Symptoms of ebola
fever, diarrhoea, vomiting; later, there is renal failure, shock and terminal haemorrhagic fever. The case fatality rate in the recent outbreak was 61%
What are the bacterial infections
-Clostridioides difficile
-Klebsiella sp.
-Bordetella pertussis (Whooping cough)
What does clostridiodes difficile cause and when does it happen
- Causes diarrhea and colitis (Test stool sample, Elisa test)
- Most infections happen after a course of antibiotics
What are the symptoms of C diff
severe diarrhoea including loose, water stools, frequent bowel movements for several days/fever/stomach tenderness or pain/nausea
What is klebsiella sp and what does it cause
-Gram-negative bacteria
pneumonia, bloodstream infections, wound or surgical site infections, and meningitis
Where is klebsiella sp found and whos at risk
- Normally found in the human intestines (not causing disease)/faeces
- Patients at risk – on ventilators or catheters/on long course of antibiotics
- Healthy individuals are usually not at risk
What is bordetella pertissis (whooping cough)
- Pertussis is a highly contagious disease of the respiratory tract
- Many children who contract pertussis have coughing spells that last four to eight weeks
- The disease is most dangerous in infants and spreads easily from person to person, mainly through droplets produced by coughing or sneezing.
When do symptoms of whooping cough appear
7–10 days after infection, and include mild fever, runny nose, and cough, which in typical cases gradually develops into a paroxysmal cough followed by whooping (hence the common name of whooping cough). - In the youngest infants, the paroxysms may be followed by periods of apnoea
Pneumonia is a common complication but what occurs more rarely
seizures and encephalopathy occur more rarely
Are untreated patienst still contagious and for how long- bordetella pertussis
Untreated patients may be contagious for three weeks or more following onset of the cough. Pertussis can be prevented by immunization.
What are prions
Prions are infectious agents that consist solely of misfolded proteins
Do prions contain genetic material like RNA and DNA
NO
What are prions associated with
can cause cellular death, missfolded proteins
several rare and fatal neurodegenerative diseases, including Creutzfeldt-Jakob disease (CJD) in humans.
What is the mechanism of prions
The exact mechanism of prion transmission is not fully understood, but it is believed to involve the transfer of prion proteins from one organism to another.
- contaminated medical equipment, such as surgical instruments, that have not been properly sterilized.
- consumption of contaminated meat or other animal products
- Blood transfusions and organ transplants (Extremely rare)
What happens when a prion enters the body
it can induce normal, healthy proteins to misfold into the abnormal, disease-causing form. This process can lead to the accumulation of prion protein aggregates in the brain
What irreversible damage can prions cause
to nerve cells and lead to the characteristic symptoms of prion diseases, such as dementia, muscle stiffness, and loss of coordination
What is the treatment of prions
There is currently no known cure for prion diseases, and treatments are limited to managing symptoms and providing supportive care.
How is prion transmission prevented
strict adherence to infection control measures, including proper sterilization of medical equipment and safe disposal of contaminated animal products
