Archive for the ‘Hantavirus pulmonary syndrome’ Category

Hantavirus syndromes part 2: the Four Corners and beyond

Wednesday, May 30th, 2012

I'm normally happy to see this sign, even in the Four Corners area

It's rare to have a "coup" in medicine, but one of mine happened just over 15 years ago. In mid-May of 1993 I was making rounds with my two staff Nephrologists and their Internal Medicine residents when I heard about a disease that had just been discovered in New Mexico. I was the "old man," the Commander of the Keesler Air Force Base medical center near Biloxi, not as current in my medical reading as my junior docs, so when I ventured a guess this would turn out to be a different Hantavirus syndrome and mentioned I have saved articles on the illness in my "War File," nobody paid much attention.

Several days later the CDC announced an unknown virus, presumed to be a Hantavirus, was causing a highly lethal pulmonary syndrome. There was an immediate scramble to borrow my War File.

El Nino had brought more rain than usual to the Four Corners area in the Fall of 1992 with a resultant growth of nuts, seeds and berries. Some of the local wild animals, including the deer mice, had markedly increased their population numbers.

The initial known victim was a young, physically fit Navajo man who had abrupt onset of breathing difficulties, was taken to a hospital and died soon afterwards.

Then it was found that his fiancé had also died, only a few days prior, with nearly identical symptoms. Another victim from the same locale and then a cluster of five others, reported independently, led to a massive effort to discover the cause. More cases turned up and 80% died.

this is how your chest x-ray should look; their's were diffusely white

Each had started with nondescript symptoms...fever, chills and muscle aches, but then they swiftly developed shortness of breath, low blood pressure and abnormal chest x-rays typical of Acute Respiratory Distress Syndrome (ARDS). That could be caused by any major injury to the lungs...trauma, severe infections, chemicals.

The short list of possible causes included Hantavirus and some of the blood samples from patients showed antibodies to several subspecies of those. No known member of the group could be be grown initially, and the causative agent was titled, Sin Nombre, "Nameless."  The new disease was named Hantavirus Pulmonary Syndrome, HPS. A laboratory test was developed to allow identification of the infecting virus from autopsy tissues and the deer mouse through its urine and droppings was thought to be the vector for the spread of the disease.

By the end of 2011, 587 cases have been reported in 34 states, with New Mexico, Colorado and Arizona leading the pack. Only 3 a year are seen in western Canada. Individuals with HPS and some outbreaks have been noted in a number of South American countries as well as Panama. Stored lung tissues from people who had died years back were examined and a Utah man who had ARDS in 1959 was found to test positive for the new virus which had eventually been grown by the Army's research lab.

Other viruses with other vector species have been reported to cause HPS. Some involve features overlapping with HFRS. An associate professor at Johns Hopkins has used satellite images to develop "risk maps" for outbreaks.

With current death rates at 35- 40%, presumably due to better handling of fluids given patients as well as discovery of milder cases, HPS is still a horrific disease.

But at least there has been no known instance of person-to-person spread.

Hantavirus syndromes part 1: The rest of the world

Saturday, May 26th, 2012

dialysis for acute kidney failure

It's been a long time since I've written about Hantavirus, but I recently saw mouse droppings in our basement storage area and that brought me back to the topic. My first knowledge of this organism came from an episode of "MASH" where Hawkeye encountered a patient with a low platelet count and acute kidney failure and had to send the man to a dialysis unit in Tokyo.  I got interested in the disease that soldier contracted and, since I was on Active Duty at the time, put it in my "War File." Years later I found articles showing exposure to the virus of longshoremen in a number of US ports and then in 1993, five young, previously healthy victims who lived in the Four Corners region, where Arizona, New Mexico, Utah and Colorado meet, died of a new manifestation of this virus.

There's a thorough paper on Hantavirus available online from the Center for Food Security & Public Health at Iowa State's College of Veterinary Medicine. The disease comes in two forms: the kind I first became aware of is hemorrhagic fever with renal syndrome (HFRS) and the newer variety is hantavirus pulmonary syndrome (HPS). There are huge differences between the two types.

Let's start with HFRS. The CDC's description of this "syndrome" (the term syndrome is normally used to describe a cluster of symptoms that together are characteristic of a disease) calls it a group of clinically similar illnesses. A number of different rodents and shrews (small, insect-eating, pointy-nosed mammals) carry the virus and four of the twenty hantavirsus subtypes identified are most frequently associated with HFRS in various countries/regions.

HFRS starts abruptly with fever, chills, headache, backache and exhaustion as the most common manifestations. After a few days to a week, severe cases develop hemorrhagic (bleeding) complications and kidney involvement with some going on to shock, kidney failure and death. Intensive nursing care, dialysis and an anti-viral medication called ribavirin are used to support the patients who have this dire form of HFRS.

The fatality rate varies considerably depending on which virus subtype is involved. For one particular hantavirus, found mostly in Europe, less than 1% of those affected may die; for the form I was first familiar with, caused by the Hantaan virus, 5 to 15% of patents will die.

Worldwide, up to 200,000 people are hospitalized with HFRS every year. Most of those cases occur in Asia (with much smaller numbers in Europe); up to 8% of the population there have antibodies indicating past infection with some form of the Hantavirus.

Other animals, including cats, dogs, pigs, horses and even moose may have antibodies to the virus, but don't appear to get sick from it.

Some mice are smarter than others.

Better than treating the disease, of course, is preventing it. Making your home or other buildings mouse-proof isn't easy, but storing food in secure containers and using traps and rodent poisons may go a long ways toward avoiding the disease. The CDC website has detailed instructions on safe ways to clean up rodent droppings and urine. CDC warns you should never start by sweeping or vacuuming!

Now I need to clean up the mouse debris in our furnace room.