A new strain of hypervirulent, deadly Cryptococcus gattii fungus has been discovered in the United States, a new study says.
The outbreak has already killed six people in Oregon, and it will likely creep into northern California and possibly farther, experts say...
Cryptococcus infections in humans are hardly new. And so far, the public health impact of the outbreak has been very low (understanding, of course, that the personal impact has been dreadful for a few).
Cryptococcus is a genus of fungus, though, and it is rare for people to get serious fungal infections unless they are already ill with something else, or have compromised immunity due to age or some other factor. The peculiar thing about Cryptococcus gattii is that it is causing serious infections in persons who were perfectly healthy.
This poses two problems for the clinician. For one, most clinicians in North America are unfamiliar with it, as it has not caused outbreaks here before. That is, it has not been known to cause outbreaks here before. Two, most clinicians would not suspect a fungal infection as the cause of symptoms in an otherwise healthy person. It can be difficult to diagnose a condition, when the physician is thinking that the true cause is highly unlikely.
Even so, it appears that the diagnosis is not difficult to establish, once the appropriate tests are done:
Clinical presentation, diagnosis and management of Cryptococcus gattii cases: Lessons learned from British Columbia
Can J Infect Dis Med Microbiol. 2009 Spring; 20(1): 23-28.
The environmental fungus Cryptococcus gattii emerged on Vancouver Island, British Columbia (BC), in 1999. By the end of 2006, it led to 176 cases and eight deaths - one of the highest burdens of C gattii disease worldwide. The present paper describes three cases, and the BC experience in the diagnosis and management of this infection. All three cases presented with pulmonary findings, including cryptococcomas and infiltrates. One also presented with brain cryptococcomas. Cases were diagnosed by chest and brain imaging, and laboratory evidence including serum or cerebrospinal fluid cryptococcal antigen detection and culture of respiratory or cerebrospinal fluid specimens. Genotyping of fungal isolates confirmed infection with C gattii VGIIa. Pulmonary cases were treated with fluconazole. One patient with central nervous system disease was treated with amphotericin B followed by fluconazole. Although this infection remains rare, clinicians should be aware of it in patients with a compatible clinical presentation who are either living in or returning from a trip to BC.
But here is the rub: this is a very serious illness; see this brain MRI of a patient, to understand how serious. Moreover, the treatment with systemic antifungal medical can be harsh. (Full treatment guideline here.) Therefore, it would be good to establish the diagnosis as quickly as possible.
There is no need for people to worry about this, in more than a momentary way. While it is true that the C. gatti in the Pacific Northwest is more virulent than it is in other places, it hardly would be considered "hypervirulent," as characterized in the National Geographic article. According to an article in the Washington Post:
More disturbing, the fungus appeared to be more virulent than in Australia. There, it infects about four people per million and is rarely fatal. On Vancouver Island, the rate was 27 per million, and it was more often killing people.
The Washington State Department of Health has prepared a fact sheet about the illness, for those who are curious.
What is more of a concern is the possibility that an outbreak of a tropical disease in Canada and northwestern USA could be linked to climate change. As noted in the WaPo article (linked above):
Similar cases have been found elsewhere in British Columbia and in Washington state and Oregon. Scientists say the fungus may be thriving because of a string of unusually warm summers here. They say it is a sign of things to come.
"As climate change happens, new ecological niches will become available to organisms, and we will see this kind of thing happen again," said Karen Bartlett, a scientist at the University of British Columbia who played a central role in the search for the disease's cause.
How likely is that? Unfortunately, there probably is no way to tell. Just as you cannot attribute any single hurricane, say, to climate change, you cannot attribute one disease outbreak to climate change. Regardless, it is important for clinicians to be aware of the possibility that they will be less able to rely on their intuition when it is time to appraise the likelihood of a particular illness in a particular patient. If outbreaks such as this become more common, diagnostic challenges will become more common.
