Public health priority: High.
PHU response time: Respond to confirmed cases on the day of notification. Enter confirmed cases on NCIMS within 1 working day.
Case management: Determine if case is a food handler or cares for patients, children, elderly or the debilitated and exclude from work until two consecutive stool specimens - collected at least 48 hours apart and the first specimen collected not sooner than 48 hours post cessation of antibiotics - are culture negative. A public health order may be taken out against a case who refuses to comply. Identify the suspected food source if possible, and assess and control any on-going risk.
Contact management: Household contacts who are food handlers or who care for children, elderly or the debilitated should be excluded from work until 2 negative stool specimens taken at least 24 hours apart are obtained. Others at risk of infection should be encouraged to seek medical attention early if symptoms develop.
High
Public health investigations involve two separate scenarios:
Generally, cases are travellers recently returned from endemic areas. If there is no history of international travel, the likely source of infection should be identified as soon as possible. If the case is a food handler, a child in pre-school, kindergarten or childcare (below the age of primary school entry), or directly cares for patients, children, the debilitated or elderly, refer to Section 9. Case management for details of exclusion and screening arrangements.
Management of contacts depends on the likely source of the case’s infection and whether the contact is at higher risk for transmitting the infection. Refer to Section 11. Contact management for details of exclusion and screening arrangements for the different types of contacts.
These guidelines cover both typhoid fever, caused by Salmonella enterica, serovar Typhi (S. Typhi) and paratyphoid fever caused by Salmonella enterica, serovars Paratyphi A, B, and C. These guidelines, however, do not cover S. Paratyphi B biovar Java as this causes gastroenteritis rather than paratyphoid fever and as such is grouped with other salmonella) (1,2).
The nomenclature and classification of the Salmonella genus have changed over the years. The current classification of the causative bacterium of typhoid is Salmonella enterica subspecies enterica serovar Typhi (commonly referred to as S. Typhi) (3). A number of strains are recognised and phage typing and pulse field gel electrophoresis (PFGE) are currently used to characterise S. Typhi isolates for epidemiological purposes and in outbreak settings. Paratyphoid is caused by S. enterica, subspecies enterica serovars Paratyphi A, B, and C with the exception of S. Paratyphi B biovar Java (also called biovar L(+) tartrate(+)/biovar dT+) which does not cause a typhoid-like enteric illness (4). Globally, S. Paratyphi A is the most frequently described of the three serovars (1, 5). Little is known about serovars Paratyphi B and Paratyphi C (1).
S. Typhi – Humans are the only reservoir.
S. Paratyphi A – Humans are the only reservoir.
S. Paratyphi B and C - Humans are the principal reservoir (6). Domestic animals may also carry these serovars. Paratyphi B infections have occasionally been associated with cattle (7).
Both S. Typhi and S. Paratyphi can survive in the environment (Section 10. Environmental evaluation).
Transmission is via the faecal-oral route. Overwhelmingly, transmission is indirect by the ingestion of water and food contaminated with faeces and/or urine. Transmission by direct person-to-person contact can occur but is rare (8). Chronic carriers transmit typhoid by contaminating food as a consequence of unsatisfactory hygiene practices (12). Little is known about chronic paratyphoid carriage.
Food was identified as the source of paratyphoid A infection following an outbreak among travellers returning from Nepal (5, 8, 9). To explain the higher incidence of paratyphoid in returned travellers, authors of a Swedish study of enteric fever (typhoid fever or paratyphoid fever) surmised that travellers are more likely to be exposed to food from street vendors infected by S. Paratyphi than to persons carrying S. Typhi (10). Imported foods have also been associated with outbreaks of typhoid (11).
Typhoid - Ranges from three days to more than 60 days (depending on infective dose and host factors), but is typically 8-14 days.
Paratyphoid - The incubation period for S. Paratyphi is thought to be shorter than for typhoid, usually 1-10 days (6). However, surveillance data suggests that the incubation period for paratyphoid can be just as long as for typhoid (50).
The inoculum size and the type of vehicle in which the organisms are ingested, greatly influence both the incubation period and the attack rate (12). The infective dose for paratyphoid is higher than for typhoid (13).
Typhoid - The infectious period lasts as long as the bacteria are present in excreta, usually from the first week of illness and throughout convalescence. Left untreated, about 10% of typhoid fever patients will discharge S. Typhi for three months after the onset of symptoms (6), and 3-5% become chronic carriers (6, 14, 15). Chronic carriage may occur with or without the case ever having an acute illness. This chronic carrier state, defined as shedding the organism for more than one year, may last for many years and is more common in females, the elderly and in patients with gallstones (16, 17). Some cases have been shown to be infectious in an asymptomatic period prior to developing acute illness. Concurrent schistosomiasis and kidney stones are associated with chronic urinary carriage (6, 15).
Paratyphoid - There is less published literature on the excretion of S. Paratyphi but it appears that excretion is similar to most other salmonellae: most people will excrete it for 5-6 weeks while a small minority may continue excreting for months or even years. Prolonged biliary excretion applies in some cases, as in typhoid (7).
Typhoid – The clinical picture of typhoid can vary from asymptomatic to mild illness with low-grade fever to severe systemic disease. Age, strain virulence, infectious dose, delay before treatment, host factors (e.g. HLA type, AIDS or other immunosuppression), medication which diminishes gastric acid secretion or other causes of gastric achlorhydria, and previous vaccination, all influence the severity of disease expression (12, 18).
Presenting symptoms are typically insidious in onset and include: fever, marked headache, and malaise (6, 19). Other symptoms and signs that present in some patients include: anorexia, abdominal pain, splenomegaly, constipation, diarrhoea, relative bradycardia, non-productive cough and rose spots (clusters of pink macules on the trunk) (20).
Without antibiotic therapy, the illness may last for 3-4 weeks. After beginning antibiotics, symptoms typically abate within four days to a week. However, relapses with milder symptoms occur 2-3 weeks after the initial fever resolves in 5 to 20% of patients, depending on the antimicrobial agent used (6). The case-fatality rate is estimated to be less than 1% with prompt antibiotic treatment (21).
Incomplete immunity follows recovery from clinical disease, inapparent infection and active immunisation (6), however, infection-derived immunity has been shown to be significantly less protective than that induced by effective vaccination (22).
Chronic carriers form a crucial reservoir for the further spread of the disease through bacterial shedding in faeces and urine. Chronic S. Typhi infections can persist for decades, and although infected individuals are contagious, they are typically asymptomatic, making the identification of carriers difficult (16, 23). Approximately 25% of carriers experience no clinical manifestations during the acute phase of the disease (17). Approximately 90% of chronically-infected carriers have gallstones (16).
Depending on the clinical setting and the quality of available medical care, up to 10% of typhoid patients may develop atypical signs and serious complications (12), typically in the third week of disease. These include: intestinal perforation, hepatitis, renal failure, osteomyelitis, myocarditis, psychosis, cholecystitis, meningitis, encephalomyelitis, cranial or peripheral neuritis, Guillain-Barré syndrome, haemorrhages (causing rapid death in some patients), isolated arthralgias, severe jaundice, disseminated intravascular coagulation, thrombocytopenia, gallbladder and hepatobiliary carcinoma, and haemolytic uraemic syndrome and pneumonia (12, 14, 20, 24, 25).
Paratyphoid - Paratyphoid is clinically similar to typhoid but tends to have a more benign course(26). Relapses may occur in anywhere between 3 to 9% of cases (6, 15). The case fatality rate is estimated at approximately 0.5% (26).
Complications typically arise in the third week (15) and have been reported in 10% to 15% of cases in the United States. Meningitis, endocarditis, hepatic abscess, osteomyelitis and psoas abscess, gallbladder cancer and pancytopenia have been associated with infection (1).
Susceptibility is general, but cases in endemic areas occur mainly in pre-school children and those aged from 5-19 years. Infection risk is also increased in individuals who travel to endemic areas and those with gastric achlorhydria (6).
Travellers who return to their countries of origin, where enteric fever is endemic, to visit friends and relatives, are an identified risk group for contracting typhoid and paratyphoid (27, 28). A six-month review of typhoid and paratyphoid cases in New South Wales, showed that 85% were travellers returning from overseas after visiting friends and relatives. None of these travellers were vaccinated prior to travel (28). Similarly, in the United States of America (USA) and United Kingdom (UK), travellers returning from visiting friends and relatives accounted for the majority of enteric fever cases (29, 30).
Enteric fever remains an important public-health problem, particularly in endemic regions (including Asia, the Middle East, Africa, Latin America and the Pacific Islands). In these regions, morbidity and mortality are increasing with the emergence and worldwide spread of S. Typhi and S. Paratyphi strains that are resistant to most previously-useful antibiotics (31). The real impact is difficult to estimate because the clinical picture is often confused with that of other febrile infections. Additionally, incidence of the disease is underestimated because there are no bacteriology laboratories in most areas of developing countries (12).
In 2010, typhoid fever incidence rates ranged from <0.1 cases per 100,000 population in Central and Eastern Europe and Central Asia, to 724.6 cases per 100,000 population in Sub-Saharan Africa. In the same year, paratyphoid incidence rates ranged from 0.8 cases per 100,000 population in North Africa/Middle East to 77.4 cases per 100,000 population in Sub-Saharan Africa and South Asia (26). In 2010, enteric fever was responsible for an estimated 190,000 deaths and more than 12.2 million disability-adjusted life years (32, 33).
Locally-acquired cases of typhoid and paratyphoid in Australia are uncommon, with the vast majority of cases sporadic, and associated with international travel to endemic countries (34, 35). Outbreaks or clusters of cases in Australia are rare. In 2014, 92% of notified cases were known to have been acquired overseas (35).
There were 116 cases of typhoid fever notified in Australia in 2015 (0.5 cases per 100,000 population). The five- year mean from 2011 to 2015 was 129 cases, compared to the five- year mean for the previous five years of 96.8 cases. Typhoid fever was most frequently notified amongst younger adults (57 cases in those aged 20 to 34 years) in 2015 (35, 36).
There were 55 cases of paratyphoid fever notified in Australia in 2015 (0.2 cases per 100,000 population). Paratyphoid fever was most frequently notified amongst younger adults (29 cases in those aged 20 to 34 years).
S. Typhi is believed to be the dominant cause of enteric fever in most endemic countries, but the proportion of infections attributed to S. Paratyphi A has been increasing in Asia, especially India and China (37, 38). A greater number of cases of enteric fever in travellers returning to the UK and Sweden were reported to be caused by S. Paratyphi, compared to S. Typhi (10, 20, 27). However, this trend has not been reported in Australia (28).
A vaccine is only available for typhoid fever. Typhoid vaccination is not routinely recommended in non-endemic countries such as Australia. Vaccination is recommended for:
* Oral live attenuated vaccine is not recommended for use in children aged <6 years.
Travellers visiting friends and relatives in countries where typhoid is endemic should be encouraged to be vaccinated prior to travel and doctors providing travel advice to such travellers should be reminded to promote vaccination for this group. A list of endemic countries is available from the International Association for Medical Assistance to Travellers web site
For further information on vaccination, see the current edition of The Australian Immunisation Handbook
To reduce the transmission of enteric fever within Australia by allowing:
To monitor the epidemiology of the disease in order to better inform prevention strategies.
To evaluate the effectiveness of public-health programs and other interventions to reduce infection.
Laboratory definitive evidence of a new case of typhoid or paratyphoid infection should be notified to the local public health unit (PHU) [and entered onto the NSW Notifiable Conditions Information Management System (NCIMS)] within one working day. Notifications are made by doctors and laboratories to [NSW PHUs] under the provisions of the [NSW Public health Act 2010].
Enter faecal clearance results, where applicable, onto [NCIMS].
For data recording purposes, a case should be counted as a second episode of disease only when a distinctly-different strain of S. Typhi/Paratyphi has been reported in patients who have previously resolved typhoid/paratyphoid. This is to differentiate a new case with a relapse of primary infection in a resolved case who has become reinfected. A new infection can occur following recovery from typhoid/paratyphoid as acquired immunity following clearance of a primary infection with antibiotic treatment is insufficient to prevent reinfection (39).
Pathology laboratories notify the [local PHU] on microbiological confirmation of a case of S. Typhi or S. Paratyphi, by telephone, facsimile, or electronic means. A PHU staff member investigates the case and records case details in [NCIMS]. On completion of the investigation of a confirmed case, the PHU should prepare a report for CDB. The report should include: the patient’s age, sex, date of onset, laboratory status, travel status, possible sources of infection, other people thought to be at risk, and follow-up action taken [CDonCall template].
If the case is a resident of another Australian state or territory, the CDB will refer the case for investigation to the appropriate CDB in that jurisdiction. Similarly, if a contact of a case (Section 11. Contact management) is a resident of another Australian state or territory, the CDB will coordinate contact follow-up with the CDB in that jurisdiction.
Cases of locally-acquired enteric fever infection should be investigated locally and reported to OzFoodNet to assist with detection of a widely-distributed outbreak within Australia.
[Enteric oncall] should be advised immediately if an outbreak (two or more locally-acquired cases not resulting from transmission within a household), is suspected. [Enteric oncall will notify CDB manager, who will inform] CDNA. CDNA and OzFoodNet will coordinate investigations if a multi-jurisdictional outbreak of typhoid or paratyphoid fever is detected. CDB may need to inform a range of other agencies in the event of a potential outbreak of typhoid or paratyphoid, including the: [NSW Food Authority (NSWFA)]; local government health authority; Coroner (if a death occurs as part of an outbreak); and Commonwealth Department of Health through HealthOps.
Only confirmed cases should be notified.
Confirmed case
A confirmed case requires Laboratory definitive evidence only.
Laboratory definitive evidence:
Case definitions can be found on the Department of Health’s website .
Definitive diagnosis of typhoid or paratyphoid fever is by culture of the organism from blood, faeces, bone marrow or urine. The causal organisms can be isolated from blood early in the disease and from urine and faeces after the first week (7). The sensitivity of blood culture ranges from 45-70% for S. Typhi (40). A large volume of blood and early collection of samples from patients improves sensitivity (21). Culture of bone marrow aspirate is more sensitive than blood culture and is of value in patients who have commenced treatment (6), who have a long history of illness and for whom there has been a negative blood culture with the recommended volume of blood, where the diagnosis is still being considered. Sampling of marrow is not often performed because it requires skill and specialised equipment, and it is an invasive procedure (41).
Faecal culture is not usually positive during the early phase of the disease. The sensitivity of faecal culture increases with the duration of the illness. However, bacterial shedding in faeces is irregular and the sensitivity of faecal culture depends on the amount of faeces cultured and number of samples tested. Antigen excretion in urine is intermittent and the sensitivity of urine culture is less than 1% (21).
Antibiotic resistance among S. Typhi and S. Paratyphi isolates is increasing in many endemic countries (7), and multidrug-resistant strains have been isolated, as well as isolates with poor susceptibility to fluoroquinolones. In vitro susceptibility should be determined for all cultured strains, to guide antimicrobial treatment.
Differentiation of S. Paratyphi B from S. Paratyphi B biovar Java requires special laboratory testing. This testing is important because S. Paratyphi B biovar Java causes a typical Salmonella gastroenteritis instead of enteric fever (42) and may not require the same public-health follow-up.
Serology is of little use for public-health management and is not recommended routinely (7). Serological testing may occasionally be useful in cases in whose cultures are negative (because of delays in diagnosis or treatment). Salmonella O-agglutination (Widal) titres of >200 in unvaccinated individuals, are associated with infection with S. Typhi; however this test has low sensitivity and is no longer widely performed. Newer serologic assays for S. Typhi infection are occasionally used in outbreak situations and are more sensitive and specific than the Widal test, but are not an adequate substitute for blood, stool, urine or bone marrow culture (21). Note that serology results in the absence of positive culture do not meet the case definition of a laboratory-confirmed case.
Food and water samples may also be sent for culture in the event of a suspected outbreak.
Refer to Public Health Laboratory Network (PHLN) laboratory case definitions website for more detailed information on tests.
Begin the follow-up investigation within one working day of notification of a confirmed case.
Public health follow up includes:
Refer to Appendix 1: Case Investigation Check List for a Case Investigation Check List.
The response to a notification will normally be carried out in collaboration with the case’s doctor. Regardless of who does the follow-up, for confirmed cases, PHU staff should ensure that action has been taken to:
[The Typhoid and Paratyphoid investigation form is available to assist in the case interview - see Appendix 2].
Each case should be assessed to decide if their illness is travel-related. As a general rule, cases who develop symptoms within 28 days after their return to Australia from an endemic country can be considered ‘travel-related’ (7). This 28-day timeframe should be used as a guide but should not be seen as prescriptive. Cases outside or at the upper limit of the 28-day period require an assessment of other possible sources and local professional judgement of likely source, based on the individual details of each case. If the case is non-travel–related and not explainable by household transmission, and food or water within Australia is suspected as the source of infection, the initial risk assessment should be conducted [involving the PHU, CBD, the NSWFA and any other relevant parties].
Information regarding history of exposures during the period 60 days before onset of illness (10 days for Paratyphoid) should be sought, including:
Treatment is the responsibility of the treating doctor. Refer to current Therapeutic Guidelines: Antibiotics . An infectious diseases physician should be consulted about treatment for chronic carriers.
All cases should be informed about the nature of the infection and mode of transmission (refer to fact sheet for typhoid and paratyphoid at Appendix 3: [NSW Health Communicable Diseases] fact sheet for typhoid and paratyphoid fevers (enteric fever). If the case is in an occupation with a higher risk of transmitting disease (see “Isolation and restriction” below), a letter can be provided for their workplace confirming exclusion from work or requesting reassignment of duties (see example letter at Appendix 4: Sample letters). A letter of clearance to return to work can also be provided where appropriate (see example letter at Appendix 4: Sample letters).
Appendix 5: Public Health Management of cases of enteric fever flow diagram
Hospital care is often considered to be desirable during acute illness and enteric precautions should be taken while the case is ill (6). Mild cases with a good understanding of hygiene and who are compliant with taking medication, may be able to be treated at home (43).
Though there is limited evidence, the risk of transmission appears low where hygiene practices are good. However, the following groups are considered at higher risk of transmitting the disease because of occupational or personal characteristics:
All cases should be excluded from work, school, child care and swimming pools until 48 hours after resolution of symptoms. All cases should be advised not to aid in feeding or preparing food for others until at least 48 hours after resolution of their symptoms.
Food handlers, carers of patients, carers of children, carers of the elderly, and carers of others who are not able to maintain their own personal hygiene, should further be excluded from working with food or caring for people until two consecutive stool specimens - collected at least 48 hours apart and the first specimen collected not sooner than 48 hours post cessation of antibiotics - are culture negative. This includes cases who are chronic carriers. They may return to work to undertake duties other than handling food or caring for people once they have been free of symptoms for 48 hours and are continent and are able to take adequate hygiene measures.
Children in pre-school, kindergarten or child care (i.e. below primary school age) and any case who is unable to maintain their own hygiene, should be isolated (i.e. stay at home) until two consecutive culture negative stool specimens collected at least 48 hours apart and the first not sooner than 48 hours post cessation of antibiotics are obtained. Children of primary-school age or above, can return to school once they are symptom free for 48 hours, provided they are continent and are able to take adequate hygiene measures.
For establishing clearance, urine samples must be collected (not sooner than 48 hours post cessation of antibiotics and until two consecutive negative samples at least 48 hours apart) in addition to stool samples if the case is considered at higher risk of transmitting the disease (see above) and originally had any of the following:
If there is no history of any international travel, local sources of infection should be investigated.
In this situation, household-type contacts should be asked to provide stool samples even if asymptomatic and not in a group at higher risk of transmitting disease (11. Contact management). If these are negative, investigation should expand to question (and possibly request stool samples from) other contacts in an attempt to identify the source of infection for the case. Other people in contact with the case in the month prior to the onset of illness, their travel history, a history of previous typhoid-like illness and the likelihood of transmitting disease to the case based on the nature of contact, should be taken into account.
Food histories are generally only collected if the case is suspected to have acquired their illness locally and if there is no history of international travel for them and all of their household type and other contacts.
Although S. Typhi and S. Paratyphi A are strictly adapted to humans, both serovars can remain viable in the environment, surviving in water and underlying sediment for days to weeks (44, 45).
Cases in non-endemic countries suspected to be locally acquired usually result from a chronic carrier who has contaminated food, as person-to-person transmission is unlikely. If the case is a food handler and has worked while infectious, the PHU should work with the relevant local government authority or jurisdictional food authority to conduct an environmental evaluation/risk assessment (see 12. Special Situations).
Where a food source is suspected on epidemiological grounds, contact [Enteric oncall] and the [NSWFA] to arrange an environmental evaluation.
The aim of identifying contacts is to:
Contacts may be co-travellers or have had household-type contact with the case.
Co-traveller: someone who travelled with the case who shared accommodation and/or ate at least one meal with the case during the case’s incubation period and is likely to have been exposed to the same source of infection as the case (rather than someone who merely travelled on the same bus/plane as the case). They may not necessarily live with the case.
Household-type: someone who, while the case was infectious:
Vaccination is recommended for household contacts of chronic typhoid carriers but not recommended for other contacts.
Not recommended
PHU staff should manage distribution of information in the form of a letter and/or fact sheet (see Appendices 3 and 4) or direct contacts to a jurisdictional website with this information. This can be done directly or through the treating doctor or other intermediary such as a child-care director.
All identifiable contacts should:
Appendix 6: Public Health Management of contacts of enteric fever flow diagram.
If the case is a food handler and has worked while infectious, the PHU should work with the [NSWFA] and the [Enteric oncall] to conduct an environmental evaluation/risk assessment as part of a site visit to the food premises. Under the NSW Public Health Act 2010, public health directors have legislative powers to issue public health orders to direct non-compliant individuals who have typhoid fever.
Other food handlers at the facility may be at risk of enteric fever if they ate food handled by the case or shared toilets or washing facilities with the case. If other staff are at risk, they should be counselled about the potential for infection and be advised that should they develop symptoms, they should exclude themselves from work and notify the PHU. If they develop symptoms, they should have stool/blood culture specimens collected and remain away from work until results are returned negative and they have been well for 48 hours. If they develop enteric fever, they will need to be managed as a case. Self-monitoring for symptoms in food handlers at risk of infection should continue for an incubation period (pragmatically 14 days) after exposure to the case.
The environmental evaluation/risk assessment should include reports from the food handler and his/her supervisor and co-workers about their duties, hygiene practices (glove use, hand hygiene), type of food preparation/handling undertaken by the case, evidence of hygiene training, and previous assessments of the sanitation practices in the facility.
Follow-up of patrons should be considered if:
Public health actions in this situation should be guided by the risk assessment, but may include:
The following guidelines are designed to assist in deciding whether potentially-exposed patrons should be alerted via the news media. In applying these criteria and judging the risk of spread of infection, the PHU, together with food safety officers should:
High-risk food is defined as food that is handled and not subsequently cooked before consumption (e.g. salad ingredients, sandwiches, sushi, cake filling or icing, and sliced fruit).
Generally, infectious food-handler situations fall into one of three categories:
If the food handler has handled high-risk foods, but the facility manager can document receipt of approved training and implementation of an approved hazard-control system, public notification is usually not indicated, if all of the following conditions are met:
In this situation, notification of potentially-exposed patrons through the news media should be considered, especially if one or more of the following criteria are met:
Consult with CDB and departmental media units before going public. An expert panel may need to be convened to advise in difficult cases.
Other staff and clientele at the facility may be at risk of enteric fever, depending on the activities of the case whilst infectious. Thus the PHU should undertake a risk assessment considering:
If staff or clientele ate food handled by the case or shared toilets or washing facilities with the case, they may be at risk and should be counselled about the potential for infection. If at risk, clientele may be given a letter and factsheet (see Appendices 3 and 4).
The staff at risk should be advised to exclude themselves from work and notify the PHU should they develop symptoms. If they develop symptoms, they should have stool/blood culture specimens collected, and remain away from work until results are returned negative and they have been well for 48 hours. If they develop enteric fever, they will need to be managed as a case. Monitoring of symptoms should continue for an incubation period (pragmatically 14 days) after exposure to the case.
An outbreak is defined as two or more geographically, temporally or epidemiologically-linked cases (that are not the result of intra-household transmission).
PHUs should immediately inform the Communicable Diseases Branch [via enteric oncall] if a typhoid or paratyphoid outbreak is suspected. Investigation of clusters or outbreaks of enteric infection that cross [State] jurisdictional borders, should include OzFoodNet and local food authorities. It is important that investigators recognise that an infection acquired in Australia may relate to a case being investigated by another PHU or state or territory, and if so, will require a coordinated response by OzFoodNet with oversight from the Communicable Diseases Network Australia.
Investigation of clusters of typhoid and paratyphoid cases usually involves an intensive search for other related cases and identification of the infection source including food, water, or a chronic carrier. Identifying sources of infection relies on microbiological testing of suspected carriers of infection, epidemiological studies, and trace back of possible food sources. Where an internationally-distributed food source is identified causing an outbreak, the Australian Department of Health may need to inform other countries through the International Health Regulations (2005) and other international food-regulatory networks.
Typhoid fever outbreaks caused by asymptomatic carriers are usually small, prolonged, and therefore difficult to detect by routine surveillance. In the USA between 1999 and 2010, 16 of 28 outbreaks were linked to a confirmed or suspected carrier; two were linked to contaminated food, and five occurred in household contacts with an unknown source (46).
Typhoid and paratyphoid clusters and outbreaks in Australia are uncommon. The last major typhoid outbreak occurred in Victoria in 1977 with 37 cases, associated with a food handler who was a chronic carrier (47). More recently: a multi-jurisdictional outbreak of 12 cases of typhoid was investigated in 1999 relating to people travelling on a cruise ship and visiting the Kokoda Track (48); four locally-acquired cases residing in the same geographic area of Melbourne were identified in 2009 but no source was identified; and a family-associated cluster occurred in Sydney in 2013 (49).
An asymptomatic person who sheds S. Typhi or S. Paratyphi for more than 12 months.
The patient should be referred to an infectious disease physician.
Manage chronic carriers the same as others with a positive specimen (Section 9. Case management).
All household and household-type contacts of chronic carriers should be:
Household contacts of chronic carriers who are considered at higher risk for transmitting infection to others should also:
Appendix 1: Case Investigation Check List
Appendix 2: Typhoid and Paratyphoid Investigation form Typhoid and Paratyphoid Investigation form
Appendix 3: NSW Health Fact sheet for typhoid and paratyphoid fevers (enteric fever)
Appendix 4: Sample letters
Appendix 6: Public Health Management of contacts of enteric fever flow diagram