@HealthMed Every year millions of people visit beautiful
Yosemite and Lake Tahoe in the Sierra Nevada of the Western USA. The individual
risk of contracting a serious infection is low, however there are several rare
but important public health risks. These range from minor nuisance from
irritating bites by ‘no-see-ums’ to a range of serious infections.
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Yosemite National Park |
While visiting there in mid-August, there
were reports in the US press of 2 deaths from hantavirus infection, attributed to
contact in the Yosemite National Park area with deer-mice as the carrier. There
are also notices posted at other beauty spots in the Sierra Nevada not to
handle small animals; ground squirrels and other small mammals were reported to
harbour plague; ‘no-see-ums’ to be
vectors for West
Nile virus infection (around half those affected developing an encephalitis
syndrome); and ticks to carry risk of acquiring Lyme disease or the protozoal infection, babesiosis. The Centers for Disease Control in Atlanta report
that these infections are rare, however urgent treatment for infected individuals may be needed, with public health measures important.
In practice, in mid-August, whether or not
due to insect spray provided by a friendly bed and breakfast host, there was little insect activity evident - but that's the nature of 'no-see-ums'. There were plenty of small mammals keen to share visitors’
food – including grey squirrels to golden-manteled ground squirrels and marmots.
And why the lag in international media
coverage until the end of August? The regional California press appear to have
begun to cover the hantavirus
story around 16th August. The BBC and other UK
media began reporting the news from 28th August, in part perhaps
because US public health authorities had begun to alert Yosemite visitors potentially at risk, typically those who had used tents and tent-cabins into which culprit rodents may have entered.
What is hantavirus? It is one of a family of viruses. Hantavirus
infection can affect the skin, lungs, kidneys and other organs. Since the first
recognized major outbreak, affecting several thousand US soldiers in the 1950s
during the Korean War in the Hanta River region of South Korea, the virus has
been detected in many parts of the world, from elsewhere in SE Asia to Scandinavia, mainland
Europe and the USA. The type of small rodent carrier varies with geography. Clinical
illness appears be rare, with however potentially severe illness in those who are affected,
and a high mortality rate, treatment based on supportive measures.