Friday, February 02, 2018

MMWR: A Little Bit Of Seoul (Virus)

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#13,116


Just over a year ago, in CDC HAN Advisory: Seoul Virus Outbreak Associated with Home-based, Rat-breeding Facilities in Wisconsin and Illinois, we looked at the first known outbreak of the Seoul hantavirus in North America, among pet rats (and a number people exposed to them) in the upper Midwest.
Like the many emerging infectious diseases, hantavirus is a zoonotic disease; one that can be transmitted between (or are shared by) animals and humans. Luckily, the Seoul virus is one of the milder forms of hantavirus.
The clinical symptoms of hantavirus were first recognized by western medicine back in the early 1950s during the Korean war, when 3,000 UN troops stationed there were infected with a mysterious viral illness. The mortality rate was 10%-15%, with patients experiencing fever, hypotension, renal failure, and internal bleeding (disseminated intravascular coagulation).
Originally called Korean Hemorrhagic Fever, this condition is now known as Hemorrhagic Fever with Renal Syndrome (HFRS). Although it was suspected that rodents were the main epidemiological vector, the pathogen responsible wasn’t isolated until the 1970s.
Scientists have since identified dozens of viruses within the genus Hantavirus (named after the Hantaan River of Korea) from all around the world, with mortality that varies from 1%-2% for some varieties (i.e. Seoul Virus, Puumala Virus) to more than 30% for the North American Sin Nombre and South American Andes Virus.

Outbreaks of zoonotic diseases carried by pets, while rarely reported, are more common than many people believe.  A few notable examples from the past include:
All of which brings us to a CDC MMWR update on last year's Seoul virus investigation, which found the spread of this virus more widespread than previously reported.   A few excerpts from a much longer report follow:

CDC MMWR

Outbreak of Seoul Virus Among Rats and Rat Owners — United States and Canada, 2017

Weekly / February 2, 2018 / 67(4);131–134

Janna L. Kerins, VMD1,2; Sarah E. Koske, DVM3; James Kazmierczak, DVM3; Connie Austin, DVM4; Karen Gowdy, DVM5; Antonia Dibernardo6; Seoul Virus Working Group; Canadian Seoul Virus Investigation Group (Federal); Canadian Seoul Virus Investigation Group (Provincial) (View author affiliations)
 

In December 2016, the Wisconsin Department of Health Services (WDHS) notified CDC of a patient hospitalized with fever, leukopenia, elevated transaminases, and proteinuria. The patient owned and operated an in-home rattery, or rat-breeding facility, with approximately 100 Norway rats, primarily bred as pets. A family member developed similar symptoms 4 weeks later, but was not hospitalized. Because both patients were known to have rodent contact, they were tested for hantavirus infections.
In January 2017, CDC confirmed recent, acute Seoul virus infection in both patients. An investigation was conducted to identify additional human and rat infections and prevent further transmission. Ultimately, the investigation identified 31 facilities in 11 states with human and/or rat Seoul virus infections; six facilities also reported exchanging rats with Canadian ratteries. Testing of serum samples from 183 persons in the United States and Canada identified 24 (13.1%) with Seoul virus antibodies; three (12.5%) were hospitalized and no deaths occurred. This investigation, including cases described in a previously published report from Tennessee (1), identified the first known transmission of Seoul virus from pet rats to humans in the United States and Canada. Pet rat owners should practice safe rodent handling to prevent Seoul virus infection (2).

Seoul virus is an Old World hantavirus in the Bunyaviridae family. Its natural reservoir is the Norway rat (Rattus norvegicus). Rats infected with Seoul virus are asymptomatic, but can transmit the virus to humans through infectious saliva, urine, droppings, or aerosolization from contaminated bedding. Human signs and symptoms range from mild influenza-like illness to hemorrhagic fever with renal syndrome (HFRS). HFRS causes acute renal failure and can result in death; however, asymptomatic Seoul virus infections also occur. Wild Norway rats in the United States have been known to harbor Seoul virus infection (3), but transmission to humans is rare (4). Seoul virus is not known to spread from person to person. In the United Kingdom, Seoul virus transmission has occurred from pet rats to humans (5), but before this outbreak, infections had not been reported in pet rats in the United States or Canada.
        (Continue . . . .)

Summary

What is already known about this topic?

Seoul virus, a type of hantavirus, is carried by Norway rats. Humans become infected through contact with virus shed in rat urine or droppings, or inhalation of virus particles in dust from contaminated bedding. Infected rats do not develop disease, but humans can experience symptoms ranging from mild influenza-like illness to severe disease with kidney failure and death. Although infections have been previously reported in humans after contact with wild rats, Seoul virus infections had not been reported in pet rats in the United States or Canada.

What is added by this report?

This report describes the first known outbreak of Seoul virus infections in humans from contact with pet rats in the United States and Canada. This investigation identified 31 U.S. facilities with human and/or rat Seoul virus infections in 11 states, including six that exchanged rats with Canadian ratteries. Seventeen persons had recent infection with Seoul virus, eight became ill, and three were hospitalized and recovered.

What are the implications for public health practice?

Human hantavirus infections are reportable to state or local health departments in the United States. Clinicians should consider Seoul virus infection in patients with a history of rat contact and compatible symptoms. Pet rat owners and breeders should also be aware of Seoul virus and should practice good hand hygiene and safe rodent handling to prevent infection.
For more on hantaviruses, you may wish to revisit:

Washington State Reports 5th Hantavirus Case Of 2017

Upcoming COCA Call: Identification and Care of Patients with Hantavirus Disease


Hantaviruses: Of Mice And Men


MMWR: Yosemite Hantavirus

 

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