Although smallpox has been eradicated globally for more than 40 years, and the last natural outbreak of this scourge in the United States occurred in 1949, there remain other poxviruses - often carried by small mammals and arthropods - with at least some zoonotic potential around the world.
Among them are Cowpox, Camelpox, and currently of greatest concern, Monkeypox (see WHO: Modelling Human-to-Human Transmission of Monkeypox) which is endemic in central and western Africa, and has shown signs of increased transmission over the past decade (see EID Journal:Extended H-2-H Transmission during a Monkeypox Outbreak).
- Three years ago, in EID Journal: Novel Poxvirus in Proliferative Lesions of Wild Rodents in East-Central Texas, USA we looked at research into a new poxvirus discovered in east-central Texas.
- In 2017, Italian researchers isolated a new pox virus in a cat (see EID Journal Novel Orthopoxvirus and Lethal Disease in Cat, Italy).
- In 2013 two people were found infected with a novel poxvirus in Eastern Europe (and a 3rd from 2010 identified retrospectively) (see NEJM Human Infection with a Zoonotic Orthopoxvirus in the Country of Georgia).
The first case - identified in 2015 - was in a middle-aged female resident of Fairbanks, Alaska who presented to an urgent care facility with what she thought was a spider bite on her shoulder, along with fever, fatigue and tender lymph nodes (see Clin. Inf. Dis Novel Orthopoxvirus Infection in an Alaska Resident).
While she had contact with a house guest from Azerbaijan, and there were signs of small mammals around her residence, no source of exposure was determined. The virus was determined to be genetically distinct from other known poxviruses, and was likely locally acquired.
Tests for shingles and chickenpox were negative, and subsequent lab tests revealed she had a never-before-seen novel pox virus. The lesion resolved after about 6 months.
In August 2020, a different woman who also lived in the Fairbanks area presented with similar symptoms. A small grey lesion appeared on her left upper arm, followed by erythema approximately 4 days later. She reported tender axillary adenopathy, shoulder pain, fatigue, and subjective fever at night. This patient’s lesion was deroofed and submitted to the US Centers for Disease Control and Prevention (CDC) for orthopoxvirus testing. The specimen tested positive on a generic orthopoxvirus PCR assay and sequencing confirmed that it belonged to the lineage identified in 2015.
(Excerpt)In July and August 2021, two unrelated persons from the Fairbanks area presented with orthopox-like lesions to an urgent care clinic. The first patient was a young child with a lesion on the inside of her left elbow. About 4 days after the lesion first appeared, she had a mild subjective fever and axillary lymphadenopathy. These systemic symptoms lasted approximately 4 days. The lesion was substantially healed approximately 3 weeks after onset.
The second patient was a middle-aged woman with a lesion on her upper right inner thigh. In addition to her lesion, she reported lymphadenopathy and joint pain beginning about 2 days after lesion onset. Approximately 3 weeks after symptom onset, the patient remained symptomatic but was improving. The lesions from both patients were deroofed and both tested positive on a generic PCR assay for orthopoxviruses. Viral genome sequencing yielded sequences very similar to previous Alaskapox viral sequences.MethodsWe interviewed the July patient’s parent and the August patient to identify exposures including travel history, any recent illness or skin lesions in household members, and contact with animals. We focused on the period starting 4 weeks prior to symptom onset; the incubation period for Alaskapox virus infection is unknown, but that of other orthopoxvirus infections is often ≤2 weeks.5ResultsNeither patient traveled outside of the Fairbanks area in the 4 weeks prior to symptom onset and neither had household members or other contacts with skin lesions or compatible symptoms. For both patients, the only close contacts identified were family members.
Dogs and at least one cat were present in both households and the cats in both households hunted small mammals. None of the pets were observed to have had pox lesions or other characteristic symptoms. Neither patient had known direct contact with small mammals or small mammal feces.
While no specific source of infection was identified for either patient, both spent time outdoors in the Fairbanks area during the summer. The August patient spent considerable time performing yard work (e.g., cutting weeds) approximately one week before symptom onset.
CDC maintains as special division – NCEZID (National Center for Emerging and Zoonotic Infectious Diseases) – to deal with them, and more than 25 years ago the CDC established the EID Journal dedicated to research on emerging infectious diseases.
As more Alaskapox virus infections in humans are identified, some patterns are beginning to emerge. The identification of these two cases with no travel history and no epidemiologic links to other known cases provides further evidence that human cases occur following occasional spillover from an animal reservoir. The first two patients and one of the 2021 patients lived within about 10 km of Fairbanks, but one of the 2021 patients lived more than 25 km away.
All four cases occurred in persons living in low-density housing in forested areas; small mammals are widespread in these areas. The 2020 case and both 2021 cases lived with cats. Cats serve as intermediate hosts for another orthopoxvirus, cowpox virus, and can transmit the virus to humans. The potential role of cats or other pets in the epidemiology of Alaskapox virus is unknown.
Small mammal trapping in October 2020 at the residence of the patient identified in August 2020 and other locations in the Fairbanks area yielded evidence of Alaskapox virus infection in small mammals, with the most extensive evidence in voles (data pending publication). The Alaska Section of Epidemiology is continuing to work with the University of Alaska Museum and CDC to investigate the role of small mammals in Alaskapox virus transmission.
Alaskapox virus infection may be more common than initially thought. However, available evidence continues to suggest that the public health impact of Alaskapox virus is limited. No evidence of human-to-human transmission has been documented and all four known infections were detected in the outpatient setting. Increased awareness among clinicians may lead to identification of additional cases and thereby inform a fuller understanding of the geographic distribution, risk factors, and spectrum of illness.
Over the past 16 years this blog has followed dozens of EIDs, including MERS-CoV, H5N1, H7N9, H5N6, EA H1N1 G4, Zika, Chikungunya, Ebola, Lyme Disease, SFTS, Nipah and Hendra, Hantavirus, Monkeypox, The Heartland Virus, the Bourbon Virus, and many others.
While most of these emerging diseases will never pose a serious pandemic threat, the sudden emergence of the COVID-19 pandemic illustrates how quickly we can be blindsided by an obscure or unknown pathogen.
Which is why, whenever a novel virus makes the jump to humans, we take note.