This week’s big story - on the multi-state outbreak of fungal meningitis – is a not-so-gentle reminder that while bacteria and viruses may get the bulk of our infectious disease attention, pathogenic fungi produce their fair share of human morbidity, mortality, and misery as well.
So today, a look at three endemic (and one emerging) fungal foes that pose health risks across North America.
NOTE: While all four of these fungal diseases are capable of causing rare but serious illness - they are only contacted from the environment - they do not transmit from person-to-person.
I’d never heard of our first entry until I first arrived in Phoenix in early 1975, and was given a brief `welcome to Arizona EMS’ indoctrination. My shift supervisor took a couple of hours and briefed me on threats I’d never run across in Florida.
Among them: scorpion stings, Gila Monster bites, bubonic plague, sand storms, and `Valley Fever’ . . . aka Coccidioidomycosis.
Coccidioidomycosisis is a lung infection caused by the inhalation of spores from one of two soil borne fungi - Coccidioides immitis or C. posadasii - both commonly found in the American Southwest.
Their spores can remain dormant in the desert soil for years, only to become airborne when the earth is disturbed by farming, earthquakes, construction, or windstorms.
Most of the people who live in regions where these fungi are endemic are eventually exposed and either develop brief asymptomatic infections or mild flu-like symptoms.
Severe disease – although rare – can sometimes occur. Which is why last week the CDC published a feature on Valley Fever, where they call it:
Most cases of valley fever in the US occur in people who live in or have traveled to the southwestern United States, especially Arizona and California. The map below, “Areas where valley fever is endemic,” was generated from studies in the 1950s, and shows the areas where the fungus that causes valley fever is thought to be endemic, or native and common in the environment. The full extent of the current endemic areas is unknown and is a subject for further study.
In 2011, more than 20,000 cases of valley fever were reported in the United States, but many more cases likely went undiagnosed. Researchers estimate that each year the fungus infects more than 150,000 people, many of whom are sick without knowing the cause or have cases so mild they aren’t detected.
The annual number of cases has been increasing in recent years, and this could be because of higher numbers of people exposed to the fungus or because of changes in the way cases are being detected and reported.
It Only Takes One Breath
Areas Where Valley Fever is Endemic
Anyone can get valley fever, including children. However, it is most common among older adults, particularly those 60 and older. People who have recently moved to an area where the disease naturally occurs are at higher risk for infection.
Several groups of people are at higher risk for developing the severe forms of valley fever, including:
Women in their 3rd trimester of pregnancy
People with weak immune systems, including those with an organ transplant or who have HIV/AIDS
The October edition of the EID Journal also contains a CME Activity article that examines a recent 18-year period where Valley Fever was identified as the cause of 3,089 deaths across the United States.
Jennifer Y. Huang, Benjamin Bristow, Shira Shafir, and Frank Sorvillo
Those at highest risk for death were men, persons >65 years, Hispanics, Native Americans, and residents of California or Arizona. Common concurrent conditions were HIV and other immunosuppressive conditions. The number of deaths from coccidioidomycosis might be greater than currently appreciated.
Moving on . . . another mycotic disease with a wide range in the United States is Histoplasmosis. It can be found in the Ohio River Valley and along the lower Mississippi river.
In the case of Histoplasmosis, the causative agent is Histoplasma capsulatum, a fungus which is found in bird and bat droppings. Its spores can become airborne when these droppings dry out and are picked up by the wind.
From the CDC:
Many people who are infected with the fungus do not show any symptoms. In areas of the world where the fungus is very common in the environment, many people may have been infected with Histoplasma capsulatum without having any symptoms. If symptoms occur, they usually start within 3 to 17 days after being exposed to the fungus.
In people who develop disease, the most common symptoms are similar to those of pneumonia, and include: fever, chest pains, and a dry or nonproductive cough. Some people may also experience joint pain. If the disease is not treated, it can disseminate (spread) from the lungs to other organs.
Number three on our fungal hit parade is Blastomycosis (aka Gilchrist's disease), which is caused by Blastomyces dermatitidis, which is found in decaying leaves and grass.
The CDC lists the symptoms of Blastomycosis as:
Only with about half of the people who are infected with blastomycosis will show symptoms. If symptoms occur, they usually appear between 3 and 15 weeks after being exposed to the fungus.
The symptoms of blastomycosis are similar to flu symptoms, and include fever, chills, cough, muscle aches, joint pain, and chest pain. In very serious cases of blastomycosis, the fungus can disseminate (spread) to other parts of the body, such as the skin and bones.
While the fungus that causes Blastomycosis can be found in many parts of the world, in the United States it is commonly found along the Mississippi and Ohio river basins and around the Great Lakes.
Rounding out today’s fungal quartet we’ve Cryptococcus gattii – a tropical fungus common in Australia and New Guinea that showed up unexpectedly on Vancouver Island in 1999. Since then has expanded its range into Washington and Oregon.
This fungus – a yeast really – is found in a number of species of trees (primarily Douglas fir & Western hemlock) and in the soil. It can be spread by the wind, particularly during the warmer summer months.
This fungus has a wide host range, having been found to infect humans, cats, dogs, sheep, ferrets, llamas, elk, alpacas, and even porpoises (Cite).
Unlike its better known cousin C. neoformans – which generally infects people with weakened immune system – C. gattii often infects those with healthy immune systems.
Luckily, C. gattii infection remains rare in the United States, with only about 100 cases diagnosed between 2004 –2011, mostly from Oregon and Washington (cite).
In 2010 the CDC’s Journal of Emerging Infectious Diseases published a research article on spread spread of C. gattii in British Columbia.
Volume 16, Number 2–February 2010
Eleni Galanis and Laura MacDougall
British Columbia, Canada, has the largest reported population of Cryptococcus gattii–infected persons worldwide. To assess the impact of illness, we retrospectively analyzed demographic and clinical features of reported cases, hospitalizations, and deaths during 1999–2007.
A total of 218 cases were reported (average annual incidence 5.8 per million persons). Most persons who sought treatment had respiratory illness (76.6%) or lung cryptococcoma (75.4%). Persons without HIV/AIDS hospitalized with cryptococcosis were more likely than those with HIV/AIDS to be older and admitted for pulmonary cryptococcosis.
The 19 (8.7%) persons who died were more likely to be older and to have central nervous system disease and infection from the VGIIb strain. Although incidence in British Columbia is high, the predominant strain (VGIIa) does not seem to cause greater illness or death than do other strains.
Further studies are needed to explain host and strain characteristics for regional differences in populations affected and disease outcomes.
Additional fungal pathogens of concern include:
Aspergillosis, Candidiasis, Dermatophytes, Exserohilium, Fungal Keratitis, Mucormycosis, Pneumocystis pneumonia, Sporotrichosis and others – all of which fall under the purview of the CDC’s Division of Bacterial and Mycotic Diseases, Mycotic Diseases Branch
Fungal spores are ubiquitous in our environment, and for the most part, there really isn’t very much any of us can do to prevent exposure.
Fortunately - for most of us - exposure only rarely leads to illness.
But as the CDC explains on FUNGAL DISEASE website, while serious illness may be relatively rare, mycotic diseases are a serious and growing public health issue.
Why are fungal diseases a public health issue?
Mycotic (fungal) infections pose an increasing threat to public health for several reasons. The scientific and medical staff of the Mycotic Diseases Branch is involved with prevention and control among three broad categories of fungal infections:
- Opportunistic infections such as cryptococcosis [PDF - 2 pages] and aspergillosis are becoming increasingly problematic as the number of people with weakened immune systems rises – this includes cancer patients, transplant recipients, and people with HIV/AIDS.
- Hospital-associated infections such as candidemia are a leading cause of bloodstream infections in the United States. Advancements and changes in healthcare practices can provide opportunities for new and drug-resistant fungi to emerge in hospital settings.
- Community-acquired infections such as coccidioidomycosis (valley fever), blastomycosis, and histoplasmosis, are caused by fungi that are abundant in the environment. These types of fungi live in the soil, on plants, or in compost heaps, and are endemic (native and common) throughout much of the U.S. Climate change may be affecting these fungi, as even small changes in temperature or moisture can affect their growth.
For earlier blogs on fungal disease, you may wish to revisit: