On this page
- Key messages
- Notification requirement for smallpox (variola)
- Infectious agent of smallpox (variola)
- Identification of smallpox (variola)
- Incubation period of variola virus
- Public health significance and occurrence of smallpox (variola)
- Reservoir of variola virus
- Mode of transmission of variola virus
- Period of communicability of smallpox (variola)
- Susceptibility and resistance to smallpox (variola)
- Control measures for smallpox (variola)
- Outbreak measures for smallpox (variola)
- Smallpox is an ‘urgent’ notifiable condition that must be notified immediately to the department by medical practitioners and pathology services. It is also subject to Australian quarantine.
- Smallpox is a severe, prostrating illness characterised by fever and a rash.
- It is unclear how long the smallpox vaccine provides effective immunity, but it is probably less than 10 years. Therefore, nearly everyone in Victoria and Australia are considered to be susceptible to smallpox.
- Ring vaccination will be used to control any smallpox outbreak.
Notification requirement for smallpox (variola)
Smallpox is an ‘urgent’ notifiable condition and must be notified by medical practitioners and pathology services immediately by telephone upon initial diagnosis (presumptive or confirmed). Pathology services must follow up with written notification within 5 days.
This is a Victorian statutory requirement.
Smallpox is included on the Commonwealth Quarantine List, and all cases will need to be notified immediately to the Victorian Chief Human Quarantine Officer.
Smallpox is subject to Australian quarantine.
Infectious agent of smallpox (variola)
Variola virus is a DNA virus of the genus Orthopoxvirus.
The virus used in the live smallpox vaccine is known as vaccinia virus, which is also a member of the genus Orthopoxvirus.
Identification of smallpox (variola)
Smallpox is a severe, prostrating illness characterised by fever, and a macular, papular, vesicular and pustular rash. It has a historically observed mortality rate of 30 per cent. There are three major forms. The most common form, described below, occurs in 90 per cent of cases. The remaining two are known as haemorrhagic and malignant (flat) variants. These both have significantly higher mortality (more than 95 per cent) and seem to be related to alterations in immune status.
Common smallpox begins with symptoms of fever (100 per cent), headache (90 per cent), backache (90 per cent), chills (60 per cent), vomiting (50 per cent), malaise, prostration and cough. Less commonly, pharyngitis and severe abdominal pain are observed. In pale-skinned patients, an erythematous rash sometimes accompanies the prodromal phase. This occurs rarely as a petechial rash. This may be misdiagnosed as meningococcal disease, erythema multiforme or measles.
By the 2nd or 3rd day, fever begins to descend from its peak (40.5–38.5 °C), and the eruptive phase begins, with the development of rash lesions. These lesions first appear on the buccal and pharyngeal mucosa, and then emerge on the face, forearms and hands. The rash spreads down, and within a day the trunk and lower limbs are involved.
Smallpox produces a single crop of lesions, which are distributed in a centrifugal pattern: most profuse on the face, more abundant on the forearms and lower legs than the upper arms and thighs, and often involving palms and soles. This is in contrast to chickenpox, which typically has more lesions located on the trunk and fewer on the limbs, with very few, if any, on palms and soles.
Prominent surfaces and areas most exposed to irritation are more heavily affected by the rash. Protected surfaces such as flexures and depressions (e.g. axilla) are usually spared.
The eruptive lesions appear as flat, discoloured macules that progress to firm papules on the 2nd day of the rash. These are typically described as ‘shotty’. They become clearly identifiable as vesicles on the 4th or 5th day of the rash, and progress to pustules on day 7.
Day 10 commonly sees the pustules at maximal size, and the lesions then begin to flatten. Approximately 14 days after rash onset, the pustules begin to dry up and crust. Most pustules begin to scab and separate at day 19. Lesions on the palms and soles separate last and typically leave pitted scars.
A patient is no longer infectious once all the scabs have separated from the skin, which is usually 3–4 weeks after the onset of the rash. Recovery results in complete clearing of the virus from the body and prolonged immunity.
The major differential diagnoses are chickenpox and disseminated herpes simplex infections. Other poxviruses may also present with similar lesions to smallpox.
Smallpox may be complicated by secondary bacterial skin infection, corneal scarring, keratitis, arthritis, osteomyelitis, bronchitis, pneumonitis, pulmonary oedema and encephalitis.
The diagnosis of smallpox will be made on the basis of a consistent clinical presentation, combined with the results of electron microscopy and polymerase chain reaction (PCR) testing, which will be performed at the National High Security Quarantine Laboratory at the Victorian Infectious Diseases Reference Laboratory, Peter Doherty Institute, in Melbourne.
Incubation period of variola virus
The incubation period is regarded to be 7–17 days, with a median of 12 days.
Public health significance and occurrence of smallpox (variola)
In 1980, the World Health Organization (WHO) declared smallpox the first communicable disease ever to be globally eradicated. This was a direct consequence of the Global Smallpox Eradication Program and was achieved by a population-based smallpox vaccination strategy.
The virus has been retained legally under strict security in two WHO collaborating centres in the United States and the Russian Federation.
The virus is believed to have been part of the bioweapons research of certain countries, and there have been recent concerns that nonstate actors may obtain access to the virus for deliberate release.
A single confirmed case of smallpox would prompt a global public health alert from WHO and would raise the spectre of an intentional release.
Historically, smallpox has a significant mortality, and it would be reasonable to expect a greater impact on today’s unimmunised and older populations. It is clear that an outbreak would be of extreme public concern, requiring action at the highest level of government and involving the mobilisation of significant resources.
Reservoir of variola virus
Smallpox is a disease only of humans, and there are no nonhuman hosts.
Mode of transmission of variola virus
Variola virus is most frequently transmitted from an infectious person via direct deposition of large, infective airborne droplets of saliva onto the nasal, oral or pharyngeal mucosal membranes, during close, face-to-face contact with a susceptible individual.
The generation of infectious fine-particle aerosols provides a possible, although less common, means of smallpox transmission. This may result in the infection of people involved in non–face-to-face contact with the case, with the virus carried in aerosols spread by drafts and air-conditioning systems. Such spread is most likely in instances where the case has a significant cough.
Cases may contaminate objects in their environment, including their clothing and linen, with the large droplets or aerosols during sneezing or coughing, and these fomites may serve as a further route of transmission.
Physical contact with a smallpox pustule or crusted scab may also transmit the virus. The virus has been found to survive in scabs for many years; however, encased in this form, it is not considered to represent a significant infectious risk.
Body fluids are also infectious, and care is needed in the disposal of clinical waste.
Variola virus is thought to be unlikely to survive on its own for more than 48 hours when exposed to normal environmental conditions (ambient temperature, usual humidity and sunlight).
During the smallpox era, the disease had secondary-household or close-contact attack rates of up to 80 per cent.
Period of communicability of smallpox (variola)
Patients are not infectious during the asymptomatic incubation period. They become increasingly infectious after onset of fever, and this usually results from the release of virus from oropharyngeal lesions.
For the purpose of contact tracing, cases are regarded as infectious 24 hours before the recognition of fever. Any contacts identified from this time on need suitable management.
Susceptibility and resistance to smallpox (variola)
Resolved infection confers lifetime immunity.
Pregnant women and people who are immunocompromised are more susceptible to variant forms of smallpox.
It is unclear how long the smallpox vaccine provides effective immunity, but it is unlikely to be more than 10 years. As a result, essentially all people in Victoria and Australia will now be regarded as susceptible to smallpox.
Control measures for smallpox (variola)
The Australian Government Department of Health has stockpiled a certain amount of smallpox vaccine, which will be accessed under appropriate situations.
In the event of an outbreak, there will be a stepwise process to vaccinate people who will be required to assist in containment of the outbreak, such as doctors, nurses and ambulance personnel.
All others will be offered vaccination only if they have had contact with a case or form part of a ‘ring vaccination’ control strategy.
Control of case
Any patient that raises a concern of smallpox must be notified to the Communicable Diseases Section of the department as soon as possible. A mobile smallpox care team will be dispatched to provide a swift and expert provisional diagnosis, and to implement suitable patient care and public health management.
All such patients (and their possessions) should be placed in the best available form of isolation as soon as possible. They should have limited contact with any people other than those directly involved in their care, who must wear personal protective equipment (PPE). Any air-conditioning should be turned off immediately.
All people in contact with the case or sharing the same air space (for example, hospital or practice staff, other patients) should be requested to remain in a safe area until the smallpox care team arrives and makes an assessment. They may need to be given access to smallpox immunisation in the short term. Their details, including contact numbers, must be collected. This should be commenced as soon as practicable. The smallpox care team will advise about infection control matters, including disinfection, and provide information to those present.
Cases will be categorised as possible, suspected, probable or confirmed, depending on the epidemiology, clinical presentation, and results of electron microscopy and PCR testing of vesicular fluid.
All confirmed and probable cases will be managed in the treatment ward of the smallpox care centre, where they will receive optimal healthcare by staff who have been successfully immunised, while maintaining appropriate isolation precautions for the community.
Those who meet the possible or suspected criteria will be placed in the observation ward of the smallpox care centre.
Control of contacts
The strategy of ring vaccination will be used in the control of any smallpox outbreak. This means that all contacts of a case (see ‘Category A – primary contacts’ and ‘Category B – primary contacts’) will be immunised. As an extra precaution, people with ongoing household contact with category A contacts, during the formal monitoring period, will also be offered access to the vaccine.
Category A – primary contacts
These are people who are likely to be exposed to the virus through large droplets or contaminated fomites. They include:
- household contacts – all usual residents, and any visitors who spent more than 1 hour at the address during the infectious period
- face-to-face contacts (within 2 metres) during the infectious period – this will include work and social settings, as well as unvaccinated healthcare and emergency services personnel
- fomite contacts – all people with direct contact with clothing or articles that have been used by infectious cases of smallpox.
Actions required:Urgent vaccination, preferably before day 3 but up to day 7.
- Active surveillance for 17 days after the last exposure, involving
- daily reporting of the contact by phone to the department; if there is failure to contact, the department will actively follow up cases by phone or in person
- details of oral temperature and presence of constitutional symptoms.
• Restriction of movement from 7 days after first exposure until 17 days after last exposure. During this time, the contact must
o avoid contact with unvaccinated people
o stay away from school and work
o remain within local area, as defined by the department.
- If symptomatic, category A cases need to stay at home and immediately contact the department.
- A category A contact who develops fever will be regarded as a possible case and transferred immediately to the observation ward of the smallpox care centre.
- A category A contact who develops fever and rash will be regarded as a probable case and transferred immediately to the treatment ward of the smallpox care centre.
- Outside the restricted period, category A contacts will need to stay within the local area until their vaccination site is completely healed and their formal monitoring period is over.
Category B – primary contacts
These contacts are less likely to have been exposed to the virus than category A contacts. They include all people who have shared a room or other enclosed spaces with the case while infective and not meeting the criteria of category A contacts.
They may include those who have visited the same premises, travelled on the same public transport (trains, planes or buses), or shared the same floors of buildings or the same air-conditioning space as an infectious case.
- Vaccinate unless contraindicated.
- Commence passive surveillance.
- Details will be taken by the department, and information provided about the nature of smallpox and actions to be taken if symptoms (fever, rash or constitutional symptoms) develop.
- If symptoms develop, they must immediately contact the department and remain at home, avoiding contact with all unvaccinated people.
- Surveillance will continue until 17 days after the last exposure to the virus.
• Restrict movement.
o Category B contacts will not be allowed to travel abroad until their vaccination site is completely healed and their formal surveillance period is over.
o No other restrictions of activity are required unless the case is unwell.
- If symptomatic, they will be admitted to the smallpox care centre.
- Category B contacts who develop fever will be classified as possible cases and transferred to the observation ward of the smallpox care centre.
- Category B contacts who develop fever and vesicular rash will be classified as probable cases and transferred to the treatment ward of the smallpox care centre.
These are people who will have ongoing household contact with category A contacts during the formal monitoring period. As such, they are at risk of exposure to the virus if the primary contact becomes symptomatic. Secondary contacts would be expected to include usual household residents of category A contacts, together with any visitors to the household who expect to spend extended periods there during the formal monitoring period.
- Vaccinate unless contraindicated.
- If vaccination is contraindicated, the secondary contact will need to avoid contact with the primary contact until the vaccination site is completely healed.
- • Passive surveillance and no restriction of movement. o No monitoring or restriction requirements are necessary unless the primary contact becomes symptomatic. If they become confirmed with smallpox, the secondary contact will be reclassified as a category A contact and will need to be managed accordingly.
Unimmunised primary contacts
These are primary contacts (both category A and B) who fail to respond to the vaccine after 3 days, who are vaccinated later than 3 days after first exposure to the virus, or who refuse to be vaccinated.
- • Limited options are available for the pharmacological management of people vaccinated late. The smallpox response team’s infectious diseases specialist may suggest the use of vaccinia immunoglobulin or cidofovir in very limited circumstances.
- • Category A primary contacts who are categorised as unimmunised will be required to remain in isolation accommodation until the incubation period has elapsed.
- Category B primary contacts will be managed as if they were a category A contact (active surveillance, restricted movement from day 7 after first exposure to day 17 after last exposure; see above).
Control of environment
All people in contact with a case of smallpox must wear the appropriate PPE. To limit any further spread, this will then be removed, and the person will be required to shower on leaving the infected area. PPE includes gloves, theatre cottons with head cover, disposable apron, eye protection, footwear such as overshoes, and a P2 respiratory mask.
Until the smallpox care team arrives, the possibly infected area should be cordoned off, and access limited to those already present and those required for urgent medical care. The case of concern should be isolated as best as possible, and all others should remain within a safe distance of the cordoned-off area. Information and care should be afforded to all people involved, with particular attention on advising that the earliest possible access to the vaccine will provide the best possible outcome if the case proves to be smallpox.
The smallpox care team will advise on suitable decontamination processes and disposal of possibly infectious materials. This will be in accordance with the Guidelines for smallpox outbreak, preparedness, response and management.
Because the virus is transmitted through infectious respiratory droplets and body fluids, or contaminated clothing, dressings, linen, towels or clinical waste, every effort must be made by relevant staff to limit spread through these routes. Air-conditioning must be isolated or turned off, and the time documented. Any object that enters the infected area must remain there until disinfected or disposed of appropriately. This includes all linen, dressings, disposable eating utensils and medical notes.
Outbreak measures for smallpox (variola)
Smallpox management will be framed in one of the five Australia response codes for smallpox:
- response code 0: smallpox remains eradicated – no credible threat of a release
- response code 1: imminent threat or a case overseas
- response code 2: one case or a cluster of related cases in Australia
- response code 3: unrelated cases or unrelated clusters in Australia
- response code 4: outbreak controlled – no further cases occurring.
Emergency plans would be activated in sequence with these codes, as outlined in the Australian Government’s Guidelines for smallpox outbreak, preparedness, response and management. This would include alerts to the community and health providers, roll-out of the smallpox vaccination strategy, mobilisation and augmentation of the smallpox care teams, and commissioning of the smallpox care centre.
General hospital wards and their emergency departments (EDs) may be at increased risk of attending to smallpox cases. To limit this, all community concerns regarding smallpox need to be notified to the department immediately. The department will dispatch a smallpox care team to make an urgent assessment. In this way, cases will be diverted to smallpox care centres without disrupting the working of any hospitals.
However, if a case does present to an ED, activation of the ED infection control procedures should be instituted, such that appropriate action is taken to limit any spread into the broader hospital.
If there are smallpox cases overseas, the Australian Government may divert all aircraft from that country to a limited number of airports, where screening, immunisation, and the appropriate isolation and quarantine measures will be applied as required.
Reviewed 08 October 2015