Information for People Handling Historical Specimens (Artifacts, Human Remains, or Zoological Specimens)

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People handling certain historical materials should consider the possibility of residual contamination with viruses and bacteria that could potentially still be viable. This includes orthopoxviruses such as Variola virus, the cause of smallpox, a serious but eradicated disease. Historical materials include, but not limited to, biological specimens (particularly human and zoological), artifacts, and library archives.

What are orthopoxviruses?

Orthopoxvirus is a genus of viruses (e.g., Camelpox virus, Cowpox virus, Monkeypox virus, and Variola virus) that generally cause skin lesions in humans and other vertebrates, most notably cats, rodents, and ungulates (e.g., camels, cows, sheep).

The most concerning Orthopoxvirus species is Variola virus, which causes smallpox. A serious disease that only affects humans, smallpox was eradicated worldwide in 1980 using vaccination with live Vaccinia virus, another Orthopoxvirus.

What are the symptoms of Orthopoxvirus infections?

Symptoms of smallpox include skin lesions such as vesicles and scabs. Vaccination with Vaccinia virus produces a localized lesion at the vaccination site. Infections with other orthopoxviruses in humans can produce similar skin lesions to smallpox but with milder symptoms.

How could orthopoxviruses be transmitted from historical specimens?

Transmission of Variola virus, Vaccinia virus, and other orthopoxviruses can occur through direct contact with skin lesions (vesicles or scabs), or through objects contaminated by them.

The viability of orthopoxviruses in well-preserved human samples (skin lesions and scabs) has not been fully determined. Environmental conditions are likely to influence the longevity of the virus. For example, lesion materials stored in dry, dark, and cool conditions can remain infectious for years. Under experimental conditions, viable Variola virus was isolated from human skin scabs stored in envelopes at room temperature for at least 13 years (researchers did not examine longer durations). Conversely, high humidity and direct sunlight will rapidly inactivate Variola virus.

Have live orthopoxviruses ever been recovered from historical specimens?

There are no published reports of residual live orthopoxviruses in historical specimens, or of human cases acquired from handling such specimens. In the United States, the CDC Poxvirus Laboratory has tested several cadavers and human skin scabs associated with smallpox infection and vaccinia vaccines. None of these yielded live Orthopoxvirus capable of infecting people.

The risk of human infection from historical specimens is low. However, the scarcity of data makes the risk difficult to assess and the possibility of live orthopoxviruses in well-preserved tissues or other materials cannot be excluded.

What historical specimens might carry orthopoxviruses?

Historical specimens include exhumed cadavers (particularly when preserved in crypts or permafrost) and artifacts contaminated by skin lesions. These might include scabs contained within envelopes, clothing, blankets, medical memorabilia (e.g., vaccination kits), or zoological specimens (e.g., hides and mounted animals).

Natural history museums or other mammalogical research collections may contain specimens that were collected from areas afflicted with Orthopoxvirus enzootics. Rodent specimens are of particular concern as certain species are putative reservoirs of members of the genus Orthopoxvirus.

When evaluating risk, collections authorities may recognize the presence of lesions consistent with orthopoxviruses or vaccine use in human or animal tissue. However, not all human or animal tissues with Orthopoxvirus infection will necessarily display visible lesions.

Managers should also consider whether specimens or artifacts originated from historical periods and areas with known Orthopoxvirus epidemics (mpox and smallpox).

Historical records indicate that smallpox outbreaks might have occurred since 1122 BCE. The last known outbreak in the United States was in 1949, and in 1980 the World Health Organization declared the disease eradicated worldwide.

What should you do if you suspect artifacts or human remains contain Orthopoxvirus?

Although smallpox has been eradicated, the possibility that it could re-emerge remains. This would have severe public health implications as routine vaccination is no longer practiced and therefore most people do not have immunity against it. If you suspect an Orthopoxvirus risk in historical materials, immediately contact your local or state public health department. State/local public health departments should call CDC at 770-488-7100 for consultation.

Because each historical object and associated account is unique and the circumstances of preservation differ, it is difficult to assess whether a material poses a risk just by looking at it. Suspicious items should be tested at state or federal public health laboratories for viable Variola virus or other orthopoxviruses before any additional work is done with the specimens.

How can you mitigate the risk of unearthing live orthopoxviruses from historical materials?

People who work with potentially contaminated historical materials, such as archeologists, museum curators, collections managers, archivists, and construction workers, should be aware of the risk of Orthopoxvirus infection and wear gloves, gown, eye protection, and a fitted respirator when handling suspect material.

Routine smallpox vaccination is no longer practiced in the United States and is reserved for military personnel and select laboratory and healthcare personnel.

References

Bits of materail thought to be smallpox scabs

This 2011 image depicts a number of what were suspected smallpox scab fragments, from the archives of the Virginia Historical Society (VHS). These fragments were uncovered when the Museum was in the process of putting together an exhibit entitled, “Bizarre Bits”, chronicling its collection dating back as far as 1831. The scabs came to the attention of Centers for Disease Control and Prevention (CDC) officials, who retrieved the items from the VHS, bringing them back to the CDC’s Atlanta headquarters for testing. The tests determined that the scab did contain virus from the smallpox vaccine, but did not contain smallpox disease, Variola virus.

pox lession crust material and chuncks of wood

Lesion crust material from a jar on display in a museum, Arkansas, USA. Photograph provided by Erin Goldman.

3 vials containing smallpox scabs

This historic 1966 image depicts three screw-top vials, each containing crusts, or scabs, collected from smallpox patients.

Variolator container from Ethiopia containing smallpox scabs

This 1976 photograph depicts what was a variolator container from Ethiopia, which had contained variolation material of a powdery consistency that was used to vaccinate people against smallpox. The powdery substance was produced through the process of grinding up dried smallpox scabs taken from a smallpox patient, which would then be used to inoculate an uninfected person, thereby, producing a less severe, milder form of the disease in the newly infected individual.

envelope that had poxvirus crust lesions in it

Lesion crust material from an envelope contained within a book, New Mexico, USA, nineteenth century. Photograph by Russell L. Regnery.