In a follow-up on the multistate Seoul virus outbreak in the United States, the Centers for Disease Control and Prevention (CDC) reports laboratory-confirmed infection in 16 people in nine states as of Feb. 23.

Image/National Park Service
Image/National Park Service

The states with laboratory-confirmed Seoul virus positive results for humans or rats include Colorado, Iowa, Illinois, Minnesota, Pennsylvania, South Carolina, Tennessee, Utah and Wisconsin.

Follow-up investigations by CDC and partnering state and local health departments indicate that potentially infected rodents may have been distributed or received in Colorado, Georgia, Delaware, Illinois, Iowa, Louisiana, Maryland,  Minnesota, Missouri, New Jersey, Pennsylvania, South Carolina, Tennessee, Utah, and Wisconsin.

Earlier this week, the World Health Organization reported the following concerning Canada:

Follow-up investigations by the United States CDC and public health officials in Canada indicate that rats have been exchanged between the United States and Canada. According to the Canada IHR national focal point report of 10 February 2017, the Canadian rat breeding facilities under investigation exported rats to the United States and also imported rats from affected United States facilities. As of 10 February 2017, three positive human cases for the Hemorrhagic Fever Renal Syndrome (HFRS) group of hantaviruses, which includes Seoul, Hantaan, Puumala and Dobrava viruses, have been identified by serology in Canada. No serious illness was reported in these individuals. Two of the cases breed rats, and the third had contact with rats.

Seoul virus is a type of hantavirus that is transmitted from rats to humans after exposure to aerosolized urine, droppings, or saliva of infected rodents, or after exposure to dust from their nests or bedding. Transmission may also occur from rat bites or when contaminated materials are directly introduced into broken skin or onto mucous membranes. For Seoul virus, the natural host is the Norway rat (Rattus norvegicus) and the black rat (Rattus rattus).

This virus has been found in both pet rats and wild rat populations around the world. The incubation period varies from 1 to 8 weeks; however, most individuals develop symptoms within 1 to 2 weeks after exposure. Seoul virus infection symptoms can range from mild to severe. In the severe form of the disease, patients can exhibit bleeding and renal syndromes. Inapparent infections can also occur. Seoul virus infection is not transmissible from human to human. There is no effective treatment available for Seoul virus infection.