11 Special pathogens

Question 1

What is definition of diarrhoea?

Answer 1

3 or more loose/watery bowel motions in 24 hour period

Take up shape of container

Liquid stool more likely to contaminate environment, and higher risk of spreading faecal pathogens

Question 2

What is period of infectivity for hepatitis A?

Answer 2

2 weeks before jaundice, until 1 week after

Question 3

Risk groups for gastroenteritis can depend on risk of spreading infection

What is included in risk groups

A
B
C
D

Answer 3

A - person of doubtful personal hygiene - e.g not washing hands

B - children who attend pre-school or nursery

C - people who are involved in preparing food

D - healthcare staff/ nursing staff in care facilities that have high risk of passing on to susceptible patients

Question 4

Rank these viral incubation period from shortest to longest

Adenovirus F40/41
Astrovirus
Sapovirus
Norovirus
Rotavirus

Answer 4

Rotavirus - 24/48 hours
Norovirus/ Sapovirus - 15-50 hours
Astrovirus - 3-4 days
Adenovirus F40/41 - 5-7 days

Question 5

Norovirus accounts for 90-95% of all gastroenteritis cases

Why is this?

Answer 5

Asymptomatic spread
Shedding after symptom resolution
Short incubation period
Low infective dose
Diarrhoea and projectile vomiting
Survive on surfaces for a long time
No immunity between norovirus genogroup infections - large susceptible reservoir

Question 6

Norovirus outbreak

How many samples should be tested to confirm an outbreak?

Answer 6

6 stool samples

Question 7

Norovirus outbreak

What actions would you take to stop an outbreak?

Answer 7

Isolate patient in side room

Isolate contacts until asymptomatic 72 hours

Consider closing the bay, or closing the ward if multiple bays affected

Visitor restriction

PPE - gloves, aprons, handwashing

Handwashing must be soap/ water as does alcohol not inactivate norovirus or C.diff spores

Clean and decontaminate rooms once patient discharged

Environmental cleaning - increase frequency of routine cleaning

Question 8

Staff member with chronic HBV infection.

e antigen neg, so considered low infectivity

When might this not be true?

Answer 8

Could have a pre-core mutant - so does not produce e antigen

Question 9

HBeAg positive pregnant lady

What is risk of transmission to baby?

Answer 9

The risk of perinatal transmission is up to 90 % in mothers who are HBV e-antigen (HBeAg)
positive and approximately 10 % in women with antibody to e antigen (Anti-HBe).

Question 10

Why is it difficult to disinfect surfaces from prions

Answer 10

The PrP Sc protein is extraordinarily resistant to standard cleaning and inactivation processes. They are highly resistant to low pH, enzymatic digestion, ionizing radiation, and detergents. They are also resistant to physical, chemical, and heat sterilization and disinfection procedures employed in the health care setting.

Question 11

What tissue is considered high risk and medium risk for CJD

Answer 11

High-risk tissue for CJD/vCJD includes brain, spinal cord, cranial nerves, specifically the entire optic nerve and the intracranial components of the other cranial nerves, cranial ganglia, posterior eye, optic nerve, and pituitary gland.

Medium-risk tissue includes spinal ganglia and olfactory epithelium. Body secretions, body fluids including saliva, blood, and cerebrospinal fluid and excreta are all low risk .