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Yellow Fever

Queensland Health Guidelines for Public Health Units

Yellow fever is quarantinable under the Commonwealth Quarantine Act (1908)

Revision History

VersionDateChanges
1.0June 2013Full revision of guidelines

Infectious agent

The infectious agent is a single-stranded RNA virus within the genus Flavivirus and family Flaviviridae.

Notification criteria

Note: While clinical evidence is required for classification/reporting/response purposes, yellow fever is not clinically notifiable under the Public Health Act.
The national case definition requires confirmation of laboratory results by a second arbovirus reference laboratory in the absence of travel history to areas with known endemic or epidemic activity. Public health management should however not be delayed in such situations.

Clinical EvidenceA clinically compatible illness.

Laboratory Definitive Evidence

  1. Isolation of yellow fever virus

    OR

  2. Detection of yellow fever virus by nucleic acid testing

    OR

  3. Detection of yellow fever virus antigen in tissues by immunohistochemistry

    OR

  4. Seroconversion or a four-fold or greater rise in yellow fever virus-specific serum IgM or IgG levels between acute and convalescent serum samples in the absence of vaccination in the preceding 3 weeks.

Laboratory Suggestive Evidence

Yellow fever virus-specific IgM detected in the absence of IgM to other relevant flaviviruses, in the absence of vaccination in the preceding 3 months.

Epidemiological Evidence

History of travel to a yellow fever endemic country in the week preceding onset of illness.

Community Outbreak Criteria

One or more confirmed cases of locally acquired yellow fever.

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Notification Procedure

Pathology Laboratories

To notify relevant public health unit (i) on receipt of request for examination by telephone or facsimile, and (ii) on confirmation of diagnosis by telephone.

Attending Medical Practitioners/Medical Superintendents (or Delegates)

Not clinically notifiable.

The Public Health Unit should immediately notify the Chief Quarantine Officer on (07) 3328 9723.

Reporting to NOCS

Report only confirmed cases.

Confirmed case: A confirmed case requires either:

  1. Laboratory definitive evidence and clinical evidence
    OR
  2. Laboratory suggestive evidence and clinical evidence and epidemiological evidence.

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Objectives of Surveillance

To identify cases so that appropriate public health action can be taken to prevent further transmission, particularly in north Queensland and other known highly receptive areas.

Public Health Significance and Occurence

Yellow fever currently occurs only in tropical parts of Africa and Central and South America. The country specific epidemiology of yellow fever changes over time so for the most up to date information of transmission risk the WHO and other reputable sources should be consulted. The presentation of infection ranges from asymptomatic (common in endemic areas) to severe and fatal disease (up to 60% of non-immune people).

There are an estimated 200 000 cases of yellow fever, causing 30 000 deaths, worldwide each year. The number of yellow fever cases has increased over the past two decades due to declining population immunity to infection, deforestation, urbanisation, population movements and climate change.

While there is no yellow fever in Australia, the principal urban vector of the virus, Aedes aegypti, is widely distributed in central, south west and north Queensland. Other mosquitoes found in Australia have been shown to be competent vectors in laboratory settings, including Aedes albopictus (established in the Torres Strait but not currently found in mainland Australia) and Aedes notoscriptus (widespread throughout Queensland and Australia). However, the potential role of these mosquito species in field settings remains unknown. The objective of Australian quarantine precautions is to prevent the introduction of yellow fever virus into Australian mosquitoes.

Clinical features

An acute viral illness of short duration and varying severity, ranging from asymptomatic infection to severe illness resulting in death. Onset is typically sudden with high fever of 39-40C, vomiting, headache, backache, generalised myalgia and prostration. Early tachycardia may evolve into a relative bradycardia (lower than expected pulse rate for the given temperature). Following remission of fever, 15% of cases progress to a second illness phase characterised by jaundice, haemorrhagic symptoms and organ failure. The case-fatality rate is about 5% in indigenous populations in endemic areas, whereas in non-indigenous individuals or during epidemics, it may be as high as 60%.

Reservoir

In urban areas: humans and Aedes aegypti mosquitoes.

In forest areas: vertebrates other than humans (especially monkeys) and forest mosquitoes.

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Mode of Transmission

There are three types of transmission cycle: sylvatic (jungle), intermediate and urban. All three cycles exist in Africa, but in South America only sylvatic and urban yellow fever occur.

The sylvatic cycle involves forest canopy mosquitoes and wild primates. The intermediate cycle occurs in humid savannahs of Africa and involves semi-domestic mosquitoes, monkeys and humans. The urban cycle involves domestic mosquitoes which carry the virus from person to person. The main urban vector is Aedes aegypti which occurs widely in Queensland.

Incubation Period

From 3 - 6 days.

Period of Communicability

There is no evidence of person to person transmission. During viraemia, bloodborne transmission theoretically can occur via transfusion or needlestick injuries. The blood of humans is infective for mosquitoes shortly before the onset of fever and for 3 to 5 days after, although yellow fever virus has been identified in blood up to 17 days after illness onset.  Mosquitoes require 9 to 12 days after a blood meal to become infectious and remain so for life.

Susceptibility and Resistence

Recovery from yellow fever is followed by lasting immunity. Second attacks are unknown. Mild, sub-clinical infections are common in endemic areas.

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Management

Cases

  • InvestigationIn consultation with the attending medical practitioner determine the vaccination status of the potential case. Determine the likely location of exposure (i.e. where the infection was presumably acquired) and locations where the case lived/worked/visited while viraemic (for public health purposes this is assumed to be 1 day before onset of fever until 5 days after onset of fever) .

    In liaison with a medical entomologist/environmental health, assess the risk of local transmission (duration of infection, possible exposure to local mosquitoes, known presence or absence of competent vector by setting appropriate mosquito traps).

  • Response management  * Share appropriate case information between local communicable disease, environmental health and medical entomology senior staff.
    * Advise the case and household contacts of preventive and restriction measures required (see below).
    * Conduct urgent house to house mosquito control, including interior residual spray, and surveys to detect other cases, in conjunction with local government (ensure staff conducting wear appropriate clothing and apply personal mosquito repellent).
    * Consider immunising anyone likely to be in contact with mosquitoes in the general vicinity of the case (including relevant response staff), depending on risk assessment.
    * Consider alerts to general practitioners, laboratories, emergency departments and the public, advising that people geographically close to the case who develop compatible symptoms should see their doctor for yellow fever testing.
    * Consider provision of personal repellent and interior residual spray to residents in vicinity of case.
  • RestrictionIsolate on suspicion of diagnosis. Case must be protected from exposure to vector mosquitoes and remain indoors in mosquito-proof surroundings (e.g. air-conditioned, enclosed buildings or in a screened room with an insecticide impregnated mosquito net) for at least 5 days from onset of fever or until fever is in remission, whichever is the later. Personal mosquito repellent and interior residual spray should also be used. As yellow fever is a controlled notifiable condition under the Public Health Act 2005, compliance can be enforced if required.
  • CounsellingThe case should be advised of the nature of the infection and its mode of transmission.

Contacts

  • Contact TracingYes
  • DefinitionAny non-immunised person who has travelled through a Yellow Fever endemic country with the case.
  • InvestigationIdentify all contacts.
  • RestrictionAdvise contacts  not to travel to north Queensland or other highly receptive areas, if possible, in the six-day period following their departure from a yellow fever endemic country. If travel to a highly receptive area is unavoidable during this period notify the relevant PHU and advise the contact to stay in airconditioned or screened accommodation and apply mosquito repellent regularly during the day. Advise contacts that if they develop symptoms during the six-day period following their departure from a yellow fever endemic country, restrictions will need to be extended until yellow fever is excluded.
  • CounsellingExplain the potential public health implications and importance of the restriction measures above. Advise all contacts to seek medical attention if they develop a febrile illness during the six-day period following their departure from a yellow fever endemic country, and to mention the possibility that they might have yellow fever. If travel to a highly receptive area is unavoidable during this six-day period, they should also be advised to contact the relevant public health unit if they develop a febrile illness during this period.

Other Control Measures

  • Border Health ProtectionUnder the Commonwealth Quarantine Act (1908) and the Quarantine Regulations 2000, people who are one year of age or older must hold an international vaccination certificate if, within six days before arriving in Australia, they have stayed overnight or longer in a yellow fever declared place. People who do not have one will be permitted to enter Australia without a vaccination certificate. On arrival in Australia, Department of Agriculture, Fisheries and Forestry Biosecurity officers will reinforce the seriousness of the disease to unvaccinated individuals and provide them with a Yellow Fever Action Card. The card provides instructions on what the unvaccinated person should do if they develop any symptom of yellow fever in the six-day period following their departure from a yellow fever declared place.
    Community Outbreaks / Epidemics

Community outbreaks/epidemics

In an outbreak an incident management team which includes a medical entomologist should be formed. Significant disease surveillance, mosquito control and educational measures will be required. Consider vaccination, depending on risk assessment. As the principal disease vector is the same, refer to the Queensland Dengue Management Plan (DMP) 2010-2015. Control measures will need to be particularly intensive given the high fatality rate from yellow fever in an immunologically naïve population.

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Preventive Measures

  • Vaccination before entering a yellow fever endemic area.
  • A live attenuated virus vaccine, Stamaril®, is available for administration to individuals over 9 months of age. While generally well tolerated, rare serious adverse events including neurotropic and viscerotropic disease occur, with higher risk in those aged > 60 years. Contraindications to vaccination include thymus conditions (due to increased risk of viscerotropic disease) and immuncompromise. Refer to the current edition of The Australian Immunisation Handbook.
  • Advice to unvaccinated travellers returning from a yellow fever endemic area.
  • Mosquito avoidance e.g. repellents, screened / air-conditioned accommodation.
  • Vector control.

Summary

Prepare a report of the investigation for the Communicable Diseases Unit, Department of Health on request.

References

Jentes ES, Poumerol G, Gershman MD, et al. The revised global yellow fever risk map and recommendations for vaccination, 2010: consensus of the Informal WHO Working Group on Geographic Risk for Yellow Fever. Lancet Infect Dis 2011; 11: 622–32.

World Health Organization. International Travel and Health 2012. Geneva, Switzerland: WHO Press; 2012.

Centers for Disease Control and Prevention. CDC Health Information for International Travel 2012. New York: Oxford University Press; 2012.

World Health Organization. Yellow fever Fact sheet N°100 (Internet). January 2011. (accessed 6/9/2012). Available from: http://www.who.int/mediacentre/factsheets/fs100/en/

Heymann D, editor. Control of Communicable Diseases Manual. 19th ed. Washington: American Public Health Association; 2008.

National Health and Medical Research Council. The Australian Immunisation Handbook. 10th ed. Canberra: Australian Government; 2013.

Queensland Government. Queensland Dengue Management Plan 2010-2015. 2011 (accessed 6/9/2012).  Available from: http://www.health.qld.gov.au/dengue/documents/dengue-mgt-plan.pdf

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Last updated: 4 July 2013