Health risks in the Sierra Nevada?

@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.

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 16^th August. The BBC and other UK media began reporting the news from 28^th 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.

Syndromes caused by hantaviruses differ across geographical regions. Typically old world hantaviruses affect predominantly the skin and kidneys, causing a ‘haemorrhagic renal syndrome’. New World viruses typified by the ‘Sin Nombre Virus’ first described in 1993 usually cause a serious pulmonary syndrome, with around 1-6 weeks incubation period.

Advances in treating acute lung syndromes

@HealthMed Although only described as recently as 1967, a range of important contributory factors have been defined for acute respiratory distress syndrome (ARDS), which is now recognized to be at the severe end of a spectrum of acute lung injury, which imposes high risk for patients and which confers a major burden on health services. Outcome of treating the syndrome has been much improved by developments in devices to treat lung and other organ failure, supported by advances in expertise in intensive care. However, other than treatments for underlying causes, there is still important unmet need with regard to effective specific pharmacological treatments.

A timely review of ARDS by Dushianthan and colleagues is the Editor’s choice article in the September issue of the Postgraduate Medical Journal.  These experts from Southampton provide an update on knowledge of risk factors, including genetic biomarkers, for development of ARDS and other acute lung injury variants, and an up-to-date commentary on general and specific treatment options.

The authors note that ‘sepsis, pneumonia, and trauma with multiple transfusions’ account for most episodes. They highlight the importance for recovery of ‘general supportive measures such as appropriate antimicrobial therapy, early enteral nutrition, prophylaxis against venous thrombo-embolism and gastrointestinal ulceration’.

They discuss encouraging experimental evidence from trials of corticosteroids, nitric oxide, prostacyclins, exogenous surfactants, ketoconazole and antioxidants, however note that these findings have not as yet being translated into benefits for patients. They note as further treatment targets of interest, new approaches to modulating inflammation, and use of mesenchymal stem cells.

See the free full article for further details.