29 August 2012
Hantavirus Pulmonary Syndrome: park visitors California, USA
On 16 August, 2012 the California Department of Public Health reported two confirmed cases of hantavirus pulmonary syndrome (HPS) in Californian tourists who stayed in Yosemite National Park on separate occasions. Both stayed in tent cabins at Curry Village in mid-June and became ill two to four weeks later. One of the tourists died [1-2]. As of 27 August, the Yosemite National Park Service reported one additional confirmed case, who died, and one suspected case. Both these cases also visited the Yosemite National Park in June 2012 . This cluster of cases are the first reports of HPS presumed to be contracted in Yosemite National Park, since a report of HPS in a visitor to Tuolumne Meadows in 2010 .
Since 1993 and as of 3 July 2012, 602 cases have been reported from 34 states of the US (50 cases from California) and 27 cases reported where the state of exposure was not known . The highest number of cases reported between 1993 and July 2012 have been in Arizona (65), Colorado (79) and New Mexico (90). 
Visitors who stayed in specific tent cabins at Curry Village from mid June to the end of August are being traced and advised to report symptoms of the infection . Yosemite National Park has also increased routine measures to reduce the risk of hantavirus exposure to park visitors. Control measures include regular inspections, cleaning of rooms and cabins, exclusion of deer mice and other rodents from buildings, maintaining good housekeeping and sanitation levels to discourage rodent infestations, and public education [1-2].
Hantaviruses are a group of viruses, with different geographical distributions and specific rodent hosts, belonging to the family Bunyaviridae.
Humans can become infected when they inhale virus particles from rodent excreta (urine, faeces or saliva). Rodent infestation in and around the home remains the primary risk for hantavirus exposure, however risk factors for rodent exposure may be linked to occupational or leisure activities.
Hantavirus Pulmonary Syndrome (HPS) is a severe, sometimes fatal, respiratory disease in humans caused by infection with a hantavirus.
Hantaviruses found only in the Americas cause HPS, and the Sin Nombre virus is the most common cause of HPS in the USA. The incubation period is typically one to two weeks and symptoms include fever, myalgia and gastrointestinal symptoms. In severe cases there can be progressive respiratory and cardiac involvement, with a case fatality rate (CFR) of 40-50% [6-7].
Advice for travellers
The risk of hantavirus in most travellers is generally considered to be low . However, those who may be in close proximity with rodents, such as travellers undertaking activities in rural areas, e.g. camping or hiking should take the following precautions:
Wash hands thoroughly before eating.
Avoid direct contact with rodents or their excreta.
Inside areas frequented by rodents should be moistened and cleaned with disinfectant and then vacuumed whilst wearing a mask and gloves.
Take measures to avoid attracting rodents, such as keeping food covered and not storing firewood inside.
Yosemite National Park has produced information on recommended precautionary measures for visitors to the park.
There is no vaccine to protect against hantavirus infection.
Information on other specific health risks for travellers can be found on the NaTHNaC Country Information Pages.
1. California Department of Public Health. Hantavirus Pulmonary Syndrome Found in Two California Residents 16 August 2012 [Accessed 29 August 2012]. Available at: http://www.cdph.ca.gov/Pages/NR12-040.aspx
2. Yosemite National Park. Hantavirus Pulmonary Syndrome. [Accessed 29 August, 2012] Available at: http://www.nps.gov/yose/planyourvisit/upload/hantavirus.pdf
3. Yosemite National Park. Hantavirus Pulmonary Syndrome Response Continues at Yosemite National Park. 27 August 2012. [Accessed 29 August, 2012] Available at: http://www.nps.gov/yose/parknews/hanta_8-27-12.htm
4. National Park Service, Office of Public Health/California Department of Public Health. Preventing Vector-Borne Diseases in National Parks in California; Summary Report 2007-2010 [Accessed 29 August, 2012]. Available at: http://www.cdph.ca.gov/programs/vbds/Documents/Preventing
5. Centers for Disease Control and Prevention. U.S. HPS Cases by State of Exposure. 3 July 2012. [Accessed 29 August 2012]. Available at: http://www.cdc.gov/hantavirus/surveillance/state-of-exposure.html
6. Health Protection Agency. Hantaviruses. [Accessed 29 August, 2012]. Available at:http://www.hpa.org.uk/Topics/InfectiousDiseases/Infections
7. Field VF, Ford L, Hill DR eds. Hantavirus. In: Health Information for Overseas Travel, National Travel Health Network and Centre, London, UK, 2010.