Communicable Disease Control. Soili Larkin & Joshna Mavji

Transcription

1 Communicable Disease Control Soili Larkin & Joshna Mavji

2 Aim To understand key principles for communicable disease control 2 Communicable Disease Control

3 Objectives Define communicable diseases Describe modes of transmission of communicable diseases Describes measures of infection prevention List key notifiable diseases Outline the role of PHE Health Protection Teams in communicable disease control Describe the process of responding to a case of communicable disease Demonstrate awareness of key communicable diseases (Meningococcal disease, E. coli, Tuberculosis, Ebola) 3 Communicable Disease Control

4 What are Communicable Diseases? Communicable diseases spread from one person to another or from an animal to a person. The spread often happens via airborne viruses or bacteria, but also through blood or other bodily fluid. The terms infectious and contagious are also used to describe communicable disease. 4 Communicable Disease Control

5 Communicable Disease Control: Modes of Transmission Contact Direct Direct physical contact (body surface to body surface) between infected individual and susceptible host. Examples: Influenza virus; Infectious mononucleosis; chlamydia. Precautions: Hand hygiene; masks; condoms. Indirect Droplet Infectious agent deposited onto an object or surface and survives long enough to transfer to another person who subsequently touches the object. Examples: RSV; norovirus; rhinovirus. Precautions: Sterilising instruments; disinfecting surfaces and toys in school. Via coughing or sneezing, or (in health care) during suctioning. Droplets are relatively large (>5 µm) and can be projected up to about one metre. Examples: Meningococcus; pertussis; scarlet fever Precautions: Masks; isolating case. 5 Communicable Disease Control

6 Communicable Disease Control: Modes of Transmission Airborne Transmission via aerosols (airborne particles <5µm) that contain organisms in droplet nuclei or in dusts. Examples: TB; measles; chickenpox; Precautions: Masks; negative pressure rooms in hospitals. Vehicle Noncontact Vectorborne A single contaminated source spreads the infection (or poison). This can be a common source or a point source. Examples a) Point source: Food-borne outbreak from infected batch of food; b) Common source: A Listeriosis outbreak in Canada was linked to a meat production facility. It caused 20 cases across nationally. Cases may be widely dispersed due to transport and distribution of the vehicle. Precautions: Normal safety and disinfection standards. Transmission by insect or animal vectors. Example: Mosquitoes malaria vector, ticks Lyme disease vector. Precautions: Protective barriers (window screens, bed nets); insect sprays; culling animals. 6 Communicable Disease Control

7 Standard Infection Prevention Precautions Hand Hygiene Single most important part of infection control Hand washing before any contact with patients, after any activity that contaminates the hands, after removing protective clothing, after using the toilet and before handling food Use of personal protective equipment (PPE): gloves, aprons, eye protection, face masks etc. Handling and disposing of sharps safely Disposing of contaminated waste safely Managing blood and body fluids: spillages and transport of specimens Decontaminating equipment: cleaning, disinfection and sterilization Preventing occupational exposure to infection Managing sharps injuries and blood splash incidents appropriately Isolation / Quarantine Correct disposal of excretions & soiled material Disinfection, especially important in nurseries, schools & residential institutions Education Routine and selective immunisation Screening 7 Communicable Disease Control

8 Notifiable Diseases (NOIDs) Acute encephalitis Acute infectious hepatitis Acute meningitis Acute poliomyelitis Anthrax Botulism Brucellosis Cholera Diphtheria Enteric fever (typhoid or paratyphoid fever) Food poisoning Haemolytic Uraemic Syndrome Infectious bloody diarrhoea Invasive group A streptococcal disease Legionnaires disease Leprosy Malaria Measles Meningococcal septicaemia Mumps Plague Rabies Rubella Severe Acute Respiratory Syndrome (SARS) Scarlet fever Smallpox Tetanus Tuberculosis Typhus Viral haemorrhagic fever (VHF) Whooping cough Yellow fever Other significant disease (diseases that may present significant risk to human health) 8 Communicable Disease Control

9 Communicable Disease Control: Role of PHE Health Protection Teams Protect the population from infection and environmental hazards through a range of core functions including: Surveillance and analysis of trends in communicable disease Operational support and advice to those involved in the prevention, investigation and control of infectious diseases and environmental hazards Education & training e.g. outbreak exercises Research 9 Communicable Disease Control

10 Communicable Disease Control: Responding to a Case What investigations (microbiological / environmental / epidemiological) are needed to identify the agent, the cause of the incident? What is the source of infection? Is it a continuing source that may need to be controlled? If so, what generic control measures can be applied to limit morbidity whilst awaiting confirmation e.g. enhanced hand washing, environmental cleaning etc. Are there others exposed who may need advice / treatment? What is the likelihood of transmission? Advice / prophylaxis to close contacts e.g. hepatitis B immunisation Occupational transmission e.g. exclusion of food handlers with gastrointestinal infection Is public health action necessary? How infectious is the source? - Is the index case at risk of a poor outcome? Is the index case likely to pass the infection to others? - How close is the contact? Do contacts and others exposed to the same source need to be traced? How susceptible are those exposed? Is there likely to be an ongoing source that needs controlling? 10 Communicable Disease Control

11 Communicable Disease Control: Responding to a Case Does public health action need to be done immediately? Determined by: Seriousness of disease Transmissibility of infection Length of incubation period Vulnerability of people exposed Public/ media / political reaction Evidence based practice Possible interventions Treatment of case Prophylaxis Isolation Hygiene advice Exclusion Closure of premises associated with incident Communication Cases / contacts / clinicians Internal - specialist advice within PHE / microbiology External - local authorities, press e.g. outbreak of meningococcal disease in a school 11 Communicable Disease Control

12 Examples of Key Infections Meningococcal disease Causal agent Meningococcal meningitis and meningococcal septicaemia are systemic infections caused by the bacteria Neisseria meningitidis. Clinical features The infection may present as meningitis, septicaemia or a combination of both 1. Sudden onset of fever, malaise, increasing headache, nausea, vomiting, photophobia, neck stiffness, non-blanching rash 12 Communicable Disease Control

13 Examples of Key Infections Meningococcal disease Reservoir Humans Mode of transmission Person to person, transmitted by droplet aerosol or secretions from the nasopharynx of colonised individuals Transmission requires either frequent or prolonged close contract Incubation period 2-10 days Period of communicability While live meningococci are present in discharges from nose and mouth. Meningococci usually disappear from the nasopharynx within 24 hours of appropriate antibiotic treatment. 13 Communicable Disease Control

14 Examples of Key Infections Meningococcal disease Epidemiology The majority of meningococcal infections occur in children under 5 years, with a peak incidence at 6 months of age. There is a smaller, secondary peak in incidence among young adults aged between years of age. Marked seasonal variation with the highest incidence occurring in winter Most cases of meningococcal disease occur sporadically, with <5% of cases occurring in clusters. Outbreaks are more common among teenagers and young adults in schools and university Since the introduction of Men C vaccine into the UK routine immunisation programme the number of laboratory confirmed group C cases have fallen by over 90% among all age groups immunised. Cases among other age groups have fallen as a result of reduced carriage rates. In the UK, serogroup B is now responsible for >85% of laboratory confirmed cases 14 Communicable Disease Control

15 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Number of Cases Seasonal Trends in Meningococcal Disease Year of Onset Confirmed Cases Three Week Rolling Average 15 Communicable Disease Control

16 Examples of Key Infections Meningococcal disease Public health management Indicated for confirmed or suspected cases Trace close contacts: close household contacts (those with an overnight stay and/or +8hrs of continuous contact), intimate contacts Antibiotic prophylaxis for close contacts - to eradicate nose and throat carriage (thus limiting further spread) and to eradicate carriage from those who may have recently acquired an invasive strain Casual contacts such as those in a same school, nursery, party etc. are not usually offered prophylaxis If the strain is found to vaccine-preventable, contacts are offered vaccination within 4 weeks of the case occurring 16 Communicable Disease Control

17 Examples of Key Infections E. coli Causal agent Many different strains of Escherichia coli can cause diarrhoeal illness The most serious is verocytotoxic E.coli (VTEC) which can cause haemolytic uraemic syndrome (HUS) which can lead to renal failure and death. Clinical features Diarrhoea (often bloody) Abdominal cramps / pain HUS is characterised by acute renal failure, haemolytic anaemia and thrombocytopaenia (lowered platelets). 17 Communicable Disease Control

18 Examples of Key Infections E. coli Epidemiology Highest incidence rates in the UK occur in children < 5 years Summer peak Reservoir Gastrointestinal tract of animals mainly cattle Mode of transmission Consumption of contaminated, undercooked or raw foods, mainly beef Consumption of unpasteurised milk Cross contamination during food preparation Person to person via faeco-oral route Direct contact with animals e.g. school visits to farms Waterborne transmission occurs through swimming in or consuming contaminated water. 18 Communicable Disease Control

19 Examples of Key Infections E. coli Incubation period 2-10 days, median 3-4 days Period of communicability Up to 1 week in adults, while excreting the pathogen Up to 3 weeks in children, while excreting the pathogen Public health management Minimisation of contamination at slaughter Good kitchen hygiene and food preparation practices Pasteurisation Effective hand hygiene Infection prevention precautions during farm visits Protection of drinking water supplies Good hygiene practices for swimming 19 Communicable Disease Control

20 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Number of Confirmed Cases Confirmed VTEC O157 Cases by Month in the West Midlands, Communicable Disease Control

21 Examples of Key Infections Tuberculosis (TB) Causal agent Mycobacterium tuberculosis Clinical features Persistent cough lasting 3 weeks or more that may produce discoloured or bloody sputum. Pain with breathing or coughing (pleurisy) Weight loss Symptoms of TB disease in other parts of the body depend on the area affected. 21 Communicable Disease Control

22 Examples of Key Infections Tuberculosis (TB) Reservoir Primarily humans In some areas diseased cattle, badgers, swine and other mammals are infected Mode of transmission Person to person via inhalation of M. tuberculosis bacilli in droplet nuclei from coughing, sneezing and talking (requires close and prolonged contact) Bovine TB is spread primarily through the ingestion of unpasteurised milk or milk products and in some cases through airborne transmission. Incubation period 3-12 weeks (from infection to reaction to tuberculin test). Latent infection may be many decades 22 Communicable Disease Control

23 Examples of Key Infections Tuberculosis (TB) Epidemiology In 1993 the World Health Organization declared TB a 'global emergency'. TB remains one of the world's leading infectious causes of death among adults. 1/3rd of the world's population is infected with the TB bacillus. Leading cause of death among people who are HIV-positive. Risk factors: Family/household contacts of cases diagnosed with TB (identified through contact-tracing), homelessness, history of alcohol/drug misuse, immigrants from high TB prevalence areas, individuals who frequently spend long periods of time in high TB prevalence areas, immunosuppression. In the UK 2/3rds of TB disease is pulmonary which is the infectious form of TB. 10% of those initially infected will eventually develop active TB disease. 90% of untreated infected individuals will never develop active TB (latent TB infection). Bacilli survive in latent form which may reactivate in later life. The risk of reactivation increases with age, chronic disease and immunosuppression. 23 Communicable Disease Control

24 Examples of Key Infections Tuberculosis (TB) Period of communicability Most sputum smear positive cases stop being infectious after 2 weeks following appropriate treatment Public health management Tuberculosis is a statutorily notifiable disease In England and Wales enhanced TB surveillance started in January In September 2005, a targeted BCG vaccination programme came into effect for: All infants living in areas where the incidence of TB is 40/100,000 population All infants with a parent or grandparent who was born in a country where the incidence of TB is >40/100,000 population. TB infection can be cured with appropriate antibiotic treatment. 24 Communicable Disease Control

25 Estimated TB incidence Rates, Communicable Disease Control

26 Tuberculosis in the UK, 2013 Source: TB in the UK: 2014 Report sis-tb-in-the-uk 26 Communicable Disease Control

27 Tuberculosis in West Midlands 27 Communicable Disease Control

28 Examples of Key Infections Ebola Virus Disease One type of viral haemorrhagic fever Causal agent Ebola virus A zoonotic virus Clinical features Initial: Fever, chills, aches and pains, malaise, lack of appetite After 5 days: nausea, vomiting, watery diarrhea, abdominal pain Additional symptoms: headache, conjunctivitis, hiccups, rash, chest pain, shortness of breath, confusion, seizures Other possible infectious causes of symptoms: Malaria, typhoid fever, meningitis and other bacterial infections (e.g pneumonia) all very common in Africa Non-fatal cases typically improve 6 11 days after symptoms onset Fatal disease associated with severe early symptoms. Case fatality rate 50-90% Intensive care, especially early intravenous fluids, may increase the survival rate 28 Communicable Disease Control

29 29 Communicable diseases Disease Control Source: en.wikipedia.org

30 Examples of Key Infections Ebola Virus Disease Epidemiology Ebola was first identified in 1976 in Sudan and the Democratic Republic of Congo following large outbreaks. Reservoir Unknown Primates and bats considered to be most likely reservoir Mode of transmission Spillover event from infected wild animals (e.g., fruit bats, monkey etc.) to humans, followed by human to human transmission Person to person via contact with bodily secretions, organs and blood of infected individuals. The handling of infected primates Direct contact with the body of a deceased person infected with the virus. Nosocomial transmission occurs frequently during outbreaks. Sexual transmission following recovery from infection virus isolated from semen upto three months after initial infection 30 Communicable Disease Control

31 Examples of Key Infections Ebola Virus Disease Incubation period 2-21 days. Period of communicability During acute illness Infectiousness of body fluids (e.g. viral load) increases as patient becomes more ill Remains from deceased infected persons are highly infectious There is no carrier state. Public health management No effective treatment is available. Severe cases require intensive supportive care. There is no vaccine against ebola haemorrhagic fever. Strict isolation of cases and strict barrier nursing techniques implemented. 31 Communicable Disease Control

32 32 Communicable Disease Control Sourcehttp://

33 Outbreaks of Ebola How do they start? Most outbreaks in remote areas Initially diagnosed as a different febrile illness e.g. Malaria, Typhoid etc. Patient cared for by relatives before they get to hospital or throughout entire illness (if they live in a remote area) so relatives become infected Health care workers become infected because disease not recognised and precautions not implemented Grieving and burial processes of infected individual e.g. holding and washing 33 Communicable Disease Control

34 Outbreaks of Ebola Current Outbreak Began in Guinea in 2013 and spread mainly to Liberia and Sierra Leone Largest outbreak on record First outbreak to affect an urban area Overwhelmed existing over-stretched health services Index case believed to be a child who died in a village in Guinea. Family members developed similar symptoms and subsequently died. As no cases had ever been reported in West Africa, these cases were diagnosed with other diseases more common to the area, therefore it took several months before it was recognised as Ebola. 34 Communicable Disease Control

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