Period of communicability There is no person-to-person transmission. The virus is generally not detectable in human blood after onset of symptoms. Mosquitoes remain infective for life. Notification procedure Attending medical practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification should not await confirmation. Management of case Investigation Confirm date of and symptoms of illness. Confirm results of relevant pathology tests or recommend test to be done (advise attending medical practitioner to take convalescent sera to confirm diagnosis). Obtain a history of travel, mosquito or insect bite and protective measures taken against insect bites. Restriction Nil. Treatment Supportive and symptomatic. Counselling Advise the case and their caregivers of the nature of the disease and its mode of transmission. Explain that having this condition may predispose a case to dengue haemorrhagic fever, which requires them to take increased precautions against mosquito bites when travelling in regions where dengue infections occur. Management of contacts Advise those exposed to the same risk factors as the index case to protect against mosquitoes for at least 2 weeks after leaving the risk area. Advise also regarding the incubation period and common symptoms of arboviral infections and encourage contacts to seek early medical attention if symptoms develop.
Management of contacts Definitions Contact Any person who has been in a confined space with the case during the period of communicability. Confined settings may include an early childhood service, classroom, household, transportation, indoor occupational or social setting. Some judgement may be required by the local medical officer of health, but noting that measles is highly infectious and this should be taken into account when determining contacts and public health action. Any person who has been in a waiting or consultation room with an infectious case, or has spent time in that room up to and including 2 hours after it has been vacated by the case must be treated as a contact. Susceptible contact Anyone born from 1 January 1969 who has not had measles infection or has not been fully vaccinated for their age. Anyone born between 1969 and 1981 who only received a single dose of measles vaccine between the ages of 10 and 15 months (because of possible interference from the mother’s antibodies). Acceptable presumptive evidence of immunity Date of before 1 January 1969 (they are presumed to be immune following exposure to the wild virus). Documentation of immunity or previous infection. Documentation of two doses of measles vaccine. If in doubt, vaccinate as there are no undue effects from vaccinating an individual who is immune. Prophylaxis For susceptible contacts, consider the use of MMR vaccine, human normal immunoglobulin (HNIG) or intravenous immunoglobulin (IVIG) as described in the Immunisation Handbook 2011. There is some evidence that a single dose of (MMR) vaccine, when given to an unvaccinated person within 72 hours of first contact with an infectious person, may reduce the risk of developing disease. HNIG is available from the New Zealand Service and can be obtained by contacting the local hospital blood bank.
Spread of infection Incubation period Gastrointestinal symptoms may appear 1–2 days after ingestion of infected meat; systemic symptoms usually appear 8–15 days (range 5–45 days) after ingestion of infected meat. Mode of transmission Humans become infected by eating raw or insufficiently cooked domestic or meat containing viable, encysted Trichinella larvae. Stomach acids degrade cysts encapsulating ingested larvae, resulting in maturation of adult worms in the small intestinal mucosa. Fertilised female worms produce hundreds of larvae over a period of 2–3 weeks and are then expelled in faeces. Newborn larvae migrate via the bloodstream to skeletal muscles, where they may remain viable for several years. The animal reservoir is perpetuated in carnivorous wild animals and in domestic animals (especially pigs) that are fed uncooked meat (for example, swill), eat infected rodent carcasses or cannibalise infected carcasses. Horses and pigs may also become infected through ingestion of larvae passed in rat faeces that contaminate feed. Period of communicability Not transmitted from person to person. Animals may remain infected for several Meat requires cooking, freezing or irradiation to kill the larvae. Freezing kills T. spiralis but not some other Trichinella spp. Notification procedure Attending medical practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification should not await confirmation. Management of case Investigation Ascertain if there is a history of travel and ingestion of inadequately cooked domestic or wild meat and the source of such meat. A definitive diagnosis is important given the potential implications for livestock and export markets. Liaise with an infectious diseases physician or microbiologist to ensure laboratory confirmation by serology has been attempted; antibodies may not become detectable until 3 weeks after infection. When a muscle biopsy is necessary (uncommon), it should be taken from a tender, swollen area of muscle. If infection is present, the uncalcified parasitic cyst will be demonstrated.
Table 2: Incubation period, mode of transmission and period of communicability of VHFs Disease Incubation Mode of transmission Period of communicability Crimean-Congo haemorrhagic fever Usually 1–3 days (1–12 days) Tick bite or crushing tick. Health care workers frequently infected by exposure to blood and secretions from cases. At least for duration of illness. Haemorrhagic fever with renal syndrome 2–4 weeks (few days to 2 months) Aerosol from infected rodent excreta (urine, respiratory secretions, saliva, faeces). Not well defined: transmission is rare. Hantavirus pulmonary syndrome 2 weeks (few days to 6 weeks) Aerosol from infected rodent excreta (urine, respiratory secretions, saliva, faeces). Not well defined: transmission is rare. Lassa fever 6–21 days Aerosol or direct contact with excreta of infected rats (commonly eaten). injury. Contact with case’s pharyngeal secretions or urine. Sexual contact. Virus present in throat during acute febrile phase, in urine for 3–9 weeks and in semen for 3 months after infection. Marburg, Ebola 2–21 days handling dead animals in the rainforest or the blood and tissues of infected monkeys. Person-to-person spread through infected blood, secretions, organs, semen and contaminated needles. Low risk in incubation period. Highest in late stages of illness. Cadaver can be infectious. May be passed through up to 7 weeks after illness. Management of case Investigation Obtain a history of travel, contact with animals, insect bites, possible contacts with infected cases, needle-stick accidents, occupation, recreational activities and any other at-risk activities. Ensure laboratory confirmation has been attempted. Restriction In health care facilities, the following isolation precautions are indicated: Crimea-Congo haemorrhagic fever: contact isolation haemorrhagic fever with renal syndrome: standard precautions hantavirus pulmonary syndrome: standard precautions Lassa fever: droplet and contact isolation Marburg, Ebola: contact isolation.
Yersiniosis Epidemiology in New Zealand The vast majority of of yersiniosis in New Zealand are caused by Yersinia enterocolitica biotype 4 (commonly found in pigs in New Zealand). Y. enterocolitica biotype 3 (commonly found in cattle in New Zealand) and Y. pseudotuberculosis account for most of the remaining cases. More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website at www.surv.esr.cri.nz. Further information on foodborne illness is available at and . Case definition Clinical description In children under 5 years old, Y. enterocolitica infection typically causes diarrhoea, vomiting, fever and occasionally abdominal pain. In contrast, older children and adults are more likely to experience abdominal pain as the prominent symptom. Bacteraemia and sepsis may occur in immunocompromised individuals. Y. pseudotuberculosis is more likely to cause mesenteric adenitis and septicaemia than Y. enterocolitica. Laboratory test for diagnosis Laboratory confirmation requires at least one of the following: isolation of Yersinia enterocolitica or Y. pseudotuberculosis from or faeces detection of circulating antigen by ELISA or agglutination test. All isolates should be sent to the Enteric Reference Laboratory at ESR for further characterisation. Case classification investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed. Probable: A clinically compatible illness that is epidemiologically linked to a confirmed case or has had contact with the same common source – that is, is part of a common-source outbreak. Confirmed: A clinically compatible illness that is laboratory confirmed. Not a case: A case that has been investigated and subsequently found not to meet the case definition.