Public health priority: Urgent.

PHU response time: Respond to any report of smallpox immediately. Immediately report suspected cases to CDB by telephone.

Data management: Enter probable and confirmed cases on NCIMS within 1 working day. Enter probable and confirmed cases on NCIMS within 1 working day.

Case management: as per the national guidelines

Complete the Smallpox Investigation Form and forward to CDB within 1 working day. Immediately initiate the investigation.

Contact management: as per the national guidelines.

The Commonwealth Guidelines for Smallpox Outbreak, Preparedness, Response and Management (2004) describes the national system of response codes that change with the risk of a smallpox outbreak [1]. The main body of the document provides
operational guidelines for each of the levels. The appendixes provide detailed information on specific topics and are referenced in the relevant areas of the text.

Smallpox is a notifiable infection in NSW under the Public Health Act 2010 and is a listed human disease under the national Biosecurity Act 2015.

Last updated: 16 September 2016
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  1. The disease
  2. Special situations
  3. Surveillance objectives
  4. Data management
  5. Communications
  6. Case definition
  7. Laboratory testing
  8. Case management
  9. Contact management
  10. References

1. The disease

Infectious agent

Variola virus, a species of Orthopoxvirus.

Smallpox was a human disease with no known animal reservoir.

Mode of transmission

Smallpox was spread from one person to another through close face-to-face contact, or direct contact with infected bodily fluid or contaminated objects, such as bedding or clothes. Smallpox can also be spread via infected aerosols, by inhaling the organism.

During the smallpox era, the disease had secondary household or close contact attack rates of up to 80%. Droplets from a symptomatic person’s respiratory tract can infect another individual by contact with their mucous membranes and respiratory tract. Although the virus is present in pustules or scabs, its infectivity from these sources is less than when it is released in respiratory secretions.

Objects around a symptomatic person, such as cutlery they sneeze on or linen on their bed, can harbour the virus and allow the infection to spread to others. Casual contact is much less likely to result in infection, although airborne spread of virus in draughts or air conditioning systems is known to cause infection.

In normal environmental conditions (ambient temperature, ordinary levels of humidity and exposure to sunlight) the virus was unlikely to survive longer than 48 hours outside of the host.

Incubation period

The incubation period ranges from 7-19 days, usually 10- 14 days.

Infectious period

Infectiousness commences with the onset of fever, increases until the onset of the rash and then remains high for the next 7 days. Cases remain infectious until the disappearance of all scabs which is usually around 3 weeks.

Clinical presentation and outcome

The first symptoms of infection include a high fever, malaise, headache, severe backache, and occasionally abdominal pain and vomiting. After 2 to 4 days the fever began to fall and the characteristic rash would gradually develop.

The rash began as macular (flat spots) rash and progresses through vesicular, (spots raised above skin and fluid accumulating inside the spots), pustular (pus-containing skin blister) and crusted (scabs) stages over the following two weeks. The lesions first appeared on the face and extremities, including the palms and soles (the centrifugal distribution) and then to the trunk; the lesions were well circumscribed and tended to all be at the same stage of development (unlike the evolving itchy lesions and centripetal distribution of the Chickenpox rash).

There were two types of smallpox clinically, Variola minor - associated with a case fatality rate of <1% - and Variola major - associated with a case fatality rate of 20-50% in unvaccinated populations. A small proportion of Variola major cases had a fulminant haemorrhagic course which was rapidly fatal.

2. Risk assessment

Smallpox was one of the most severe infectious diseases affecting humans. Before the World Health Organization (WHO) eradication campaign, smallpox was a common disease worldwide and it is estimated to have killed more than 300 million people in the 20th century.

The last community-acquired case of smallpox was in Somalia in October 1977 — almost 40 years after the last case seen in Australia. Since global eradication, the smallpox virus has been retained legally under strict security in two WHO collaborating centres: one in the United State and one in Russia.

3. Surveillance objectives

  • To identify cases and ensure that they are urgently isolated and treated
  • To urgently identify and protect contacts at risk of infection.

4. Data management

Enter probable and confirmed cases on NCIMS within 1 working day of notification.

5. Communications

Suspected and confirmed cases of Smallpox disease must be notified to public health by medical practitioners and hospital CEOs on clinical diagnosis (ideal reporting by telephone immediately), and by laboratories on diagnosis (ideal reporting by telephone immediately)

Immediately report suspected and confirmed cases to the Communicable Diseases Branch (CDONCALL) by telephone with the patient's age, sex, date of onset, laboratory status, other people thought to be at risk and follow up action taken.

CDB will immediately notify suspected, probable and confirmed cases to the National Incident Room. Confirmed cases of smallpox are notified nationally and are also required to be notified under the International Health Regulations (2005) [2].

6. Case definition

Confirmed Case

A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

  • Isolation of variola virus, confirmed at the Victorian Infectious Diseases Reference Laboratory, or
  • detection of variola virus by nucleic acid testing, confirmed at the Victorian Infectious Disease Reference Laboratory.

Probable Case

A probable case requires either: clinical evidence and laboratory suggestive evidence, or clinical evidence and epidemiological evidence.

Laboratory suggestive evidence

  • Detection of a poxvirus resembling variola virus by electron microscopy
  • Isolation of variola virus pending confirmation
  • Detection of variola virus by nucleic acid testing pending confirmation.

Clinical Evidence

Credible clinical smallpox as judged by an expert physician. Epidemiological Evidence An epidemiological link to a confirmed case.

Factors to be considered in case identification

Note that the Commonwealth Guidelines for Smallpox Outbreak, Preparedness, Response and Management includes separate case definitions for smallpox surveillance, both preceding and during an outbreak. [1]

The guidelines define confirmed, probable, suspected and possible cases for the purposes of public health response. These definitions are at slightly different from the national surveillance case definitions for reporting.

7. Laboratory testing

When a patient with suspected smallpox is identified during a response code 1 or code 2 alert, the National High Security Quarantine Laboratory (NHSQL) at the Victorian Infectious Diseases Reference Laboratory (VIDRL) will likely be tasked to carry out testing of specimens following expert review.

See the Commonwealth Guidelines for Smallpox Outbreak, Preparedness, Response and Management. [1]

8. Case management

Investigation

On notification of any possible case, immediately begin follow-up investigation, and notify Communicable Disease Branch of case details by telephone.

Response procedure

The response to a notification will normally be carried out in collaboration with the case's health carers and in consultation with an expert panel. Regardless of who does the follow up, PHU staff should ensure that the action has been taken to:

  • Ensure that the clinical team responsible for the patient is fully compliant with the infection control procedure for smallpox.
  • Confirm the onset date and symptoms of the illness
  • Confirm results of relevant pathology tests, or recommend the tests be done to find out if the case or relevant care-giver has been told what the diagnosis is before interviewing them
  • Ensure that all contacts including health workers are identified and receive appropriate post-exposure prophylaxis
  • Review case management
  • Identify likely source of infection (whether natural or deliberate).

For further advice, including advice on clinical case management, see the Commonwealth Guidelines for Smallpox Outbreak, Preparedness, Response and Management. [1]

9. Contact management

Refer to the Commonwealth Guidelines for Smallpox Outbreak, Preparedness, Response and Management. [1]

10. References

  1. Commonwealth Guidelines for Smallpox Outbreak, Preparedness, Response and Management
  2. World Health Organization. International Health Regulations (2005) .
Page Updated: Friday 16 September 2016