Posts Tagged ‘global warming’

Dengue fever and its major Mosquito vector

Saturday, June 21st, 2014

I don't like being bitten by mosquitoes any more than the rest of you do, but worldwide the real reason to avoid them, kill them or alter them is the enormous disease burden they cause. One recent estimate , surprising to me, said "mosquitoes have been responsible for half the deaths in human history." I was aware, having lived as an Air Forced physician in the Philippines and traveled in South America and Africa, that malaria was one enormously dangerous, mosquito-carried disease, but there's a long list of other illnesses that contribute to the threat from these insects.

This one doesn't carry dengue

This one doesn't carry dengue

From 1690 to 1905 major epidemics of yellow fever struck parts of southern and eastern America: Boston, New York, Philadelphia, New Orleans killing over 40,000 people. A 2006 PBS website gives short summaries of nine of the outbreaks and alludes to even larger mortality figures.

And then there's dengue, a disease primarily transmitted by the bite of infected female Aedes Aegypti mosquitoes. They don't make the telltale sound that alerts you to other mosquitoes, they also strike during daytime and may follow their human target, biting repeatedly.

Dengue attacks 400 million people every year world-wide., mostly in the tropics and sub-tropics. Three-fourths of those infected never develop symptoms and of the remaining 100 million, a large majority have a mild to moderate nonspecific acute illness with a fever. But 5% can have severe, even life-threatening disease with terrible joint and muscle pain (It's called break-bone fever), hemorrhages and shock. The World Health Organization estimates 22,000 die from dengue yearly, but other estimates range from 12,000 to 50,000.

The first known case in the United States occurred in Philadelphia in 1780 and was documented by Benjamin Rush, the distinguished physician who was a signer of the Declaration of Independence.

The Center for Disease Control and Prevention (AKA the CDC) has an entire chapter on dengue in its "Infectious Diseases Related to Travel" publication and a shorter version with links for travelers. Their maps of disease distribution focus on warmer areas in Africa, Central and South America, Asia and Oceania.

There has been no vaccine available to prevent the disease and no specific anti-viral treatment for those with severe cases of dengue. Because of known bleeding complications, those who get the dengue are advised to avoid taking aspirin or any of the nonsteroidal anti-inflammatory drugs , AKA NSAIDs, such as ibuprofen.

The continental United States was essentially dengue-free for over fifty years, but marked increases in dengue infection rates have occurred in our hemisphere, mostly in South America and Mexico.

Now Aedes Aegypti is back in Florida, Texas, and Hawaii. The article in The New Yorker mentioned a small 2009 outbreak of dengue in Key West with fewer than 30 cases, but that was the first real brush with the disease there in over seventy years. In 2010 there were twice as many cases. An entomologist (insect specialist) with the Florida Keys Mosquito Control District reminded the reporters that the manner in which the populace lived was crucial; from 1980 to 1999 there were only sixty-four cases on the the Texas side of the Rio Grande and 100 times as many just across the river.

What was the difference? Likely screens on windows, cars with AC running and windows closed and how often people were exposed outdoors. Key West, in a 2013 followup, had seen no further cases, but the World Health Organization called dengue the "fastest-spreading vector-borne viral disease," saying cases had gone up thirty-fold over half a century.

Why has this happened and what can be done about it?

How can we do this?

How can we do this?

Is this another consequence of global warming? After all dengue has appeared in France and Croatia for the first time. But I just watched an online video by Dr. Paul Reiter, a world-famous medical entomologist, who spent much of his professional career at the CDC's Dengue Control branch. It was obvious that he does not believe in man-made global warming (I do) or that any form of global temperature change is responsible for the spread of malaria or dengue.

How about used tires? He thinks they are great incubators for mosquitoes and billions of those tires have been moved around the globe. So Aedes aegypti has adapted to the city, in part because of our habit of having water-containing used tires around the places where we live.

I don't have any old tires in my yard and I change the dog's water bowl and the bird water outside frequently.

A few new ideas are out there: a British company called Oxitec has genetically modified (GM) mosquitoes, making the males able to mate, but also giving them a gene which kills their offspring soon after they hatch. An initial field trial in Brazil was successful in markedly reducing the population of disease-carrying adult females (remember, males don't bite humans for a blood meal; females do).

Further field trials of these GM-mosquities, titled OX513A, have met with considerable opposition and an engineer involved has published a paper examining the ethical issues involved. The lifespan of mosquitoes is short and they don't appear to be a major food source for other creatures; the most significant issue likely is fully informing the people in the test area are who may consider OX513A to be just another threat.

A French pharmaceutical company recently announced an experimental vaccine for dengue was moderately successful in a late-stage, placebo-controlled clinical trial involving 10,000 children in Southeast Asia, reducing dengue incidence by 56%. A similar clinical trial is underway in South America.

It's a bad disease, coming back at us, but perhaps there's some good news on the horizon.




The ongoing war: superbugs versus humanity

Tuesday, June 4th, 2013

I saw an article that gave me some hope for our current bacterial and viral dilemmas; it involved a new strategy to prevent infections, rather than treating them after they've struck. I'm all for preventive medicine, both in the infectious disease arena and in medicine in general. I think we "play catch-up" all too often.

How this ICU staffer chooses to protect you from MRSA is crucial.

How this ICU staffer chooses to protect you from MRSA is crucial.

The piece was in The Wall Street Journal on May 30, 21013 with its headline,  "New Tack in Preventing Hospital Infections: Germ-Killing Soap-Ointment Treatment for all ICU Patients Shown to be More Effective than Isolating Some After Screening" The original article  was printed online in the New England Journal of Medicine on May 29, 2013 and its title was  "Targeted versus Universal Decolonization to Prevent ICU Infection."

We're mostly talking about MRSA (Methicillin-resistant Staphylococcus aureus), that strain of the familiar Staph bacteria that's been plaguing us for the last few decades, in large part as a result of unnecessary antibiotic use.

Even if antibiotics are used only for significant bacterial infections, a small proportion of the "bugs" may survive. The population of those germs who cannot be killed by the particular antibiotic can multiply and be spread to others. When antimicrobial drugs are used inappropriately used to "treat" viral infections (e.g., "flu" or the common cold) or given wholesale to food animals (beef, chicken, pigs) to promote growth), we're also likely to be find ourselves with bacteria that are resistant to those antibiotics we've previously been able to use successfully.

About 30% of us carry staph of our skin or in our nostrils (without being ill) and somewhere between 1% and 2.5% carry MRSA. Otherwise healthy people can develop infection with it as a painful skin boil, especially in rugby or football players and high school wrestlers, but also in those who are child care workers or live in crowded settings.

Since moving here in 1999 I'm personally aware of two people who started with what seemed to be very minor skin infections, but later were diagnosed with extremely serious progression of their initial disease. One died from what was eventually diagnosed as fleshing-eating Strep; the other survived, but spend a long time in intensive care with a Staph infection that spread from a bump on his arm up to his chest.

Hospitals often screen patients for MRSA and nine states now mandate such screening. But the study mentioned above attempted to see if there was a better way to avert serious infections in the intensive care setting where patients are the sickest.

MRSA growing on a culture plate.

MRSA growing on a culture plate.

Forty-three hospitals with 74 ICUs and nearly 75,000 patents were randomly assigned to one of three infection prevention strategies: the first group screened patents for MRSA and isolated those who tested positive; the second group added "decolonization," removing the bacteria by washing MRSA-positive patents with an antimicrobial (bacteria-killing) soap plus giving them a nasal antibiotic; the third group of hospitals did not screen patents, but treated every ICU patient as though they had MRSA, i.e., with the soap and the nasal antibiotic.

Universal decolonization cut the rate of positive blood cultures, a way to look at the most serious infections, by 44%. That included not only Staph, but other bacteria as well. Only seven of the research subjects had any form of adverse reaction and those were mild rashes of itching; all resolved after stopping the washing.

The Mayo Clinic webpage on MRSA discusses risk factors for hospital-associated MRSA infections (HA-MRSA) and for those that are community-associated (CA-MRSA). Just being hospitalized increases your risk as does having an invasive medical device (urinary catheter or IV line) and residing in a long-term care facility. Remember, carriers of MRSA can spread the germ, even if they are not sick from it. For CA-MRSA the risk factors include contact sport, living in crowded or unsanitary conditions and men who have homosexual relations.

The World Health Organization (WHO) has an online fact sheet on Antimicrobial resistance. Infections that fail to respond to conventional therapy result in higher medical care costs, greater length of illnesses and a higher risk of a fatal outcome.

MRSA is by no means the only germ that has developed drug resistance. WHO estimates over 630,000 cases of multi-drug resistant tuberculosis (MDR) requiring longer therapy with more drugs. Malaria, caused by one of five species of a parasite that are carried by mosquitos, has become increasingly difficult to treat because of this issue. Malaria cases in the United States have been relatively rare, about 1,200 per year while annually there are 300 million cases and one million deaths from the disease elsewhere in the world.

Most US cases have occurred in those who travel to sub-Saharan Africa, India, or Southeast Asia; That is likely to change as the expected average temperature increase of 0.4 degrees Celcius over the next eight years will likely increase our mosquito population by up to 30%, including the one mosquito species that carries the Plasmodium falciparum, the most deadly type that I've only seen when I was serving at the Air Force Regional Medical Center located on Clark AFB in the Philippines.

A recent online copy of The New York Times has an article titled, "Pressure Grows to Created Drugs for Superbugs." Health and Human Services (HHS) is going to pay $40 million to a pharmaceutical company to develop new antibiotics to combat drug resistance; they are concerned about biological agents that terrorists may utilize to cause widespread death.

But in the meantime, tens of thousands of our citizens die from inceptions, mostly hospital-acquired and caused by the current generation of antibiotic resistant germs. The FDA's director of the Center for Drug Evaluation and research was quoted as saying, "We are facing a huge crisis worldwide not having an antibiotic pipeline... but what is worse is the thought of where we will be five to 10 years from now."

A move to fast-track approval of new anti-infective drugs is being hotly debated. The Infectious Disease Society of America would support their labeling for use on only the very sickest patients.

Others are concerned that these restrictions are insufficient; that the new medicines will be used for those less-than critically ill without our knowing how the antibiotics will perform and what their advise effects may be. One director of the infectious disease society said, "The last thing we want is for a new drug to be overused."

The next twenty to fifty years will be a critical time for the germs versus humans war.

Biofuels, greenhouse gases and you: Part one of many

Thursday, November 17th, 2011

Not the right choice for a sustainable biofuel

The excursion into what was initially a vaguely known arena started with a Wall Street Journal article on 11-8-2011, but then strayed far afield as my learning curve tilted steeply upward.

The article itself dealt with airlines trying out newer biofuels: Alaska Airlines and United were highlighted as having pilot projects in this area. As I read further, scanning online material, international carriers, especially KLM, with 200 flights using 50% biofuels and, impressively, Lufthansa with 1,200 flights using 50% biofuels, are far ahead in this arena.

The fuels come not from corn, as in the United States, or sugarcane, as in Brazil (more on the latter in a subsequent post), but rather from algae, cooking oil, animal fat, and two plants I'd never heard of, Camelina (I'm trying to find it as a cooking oil) and Jatropha.

We had dinner company a few days ago; I was cooking a cabbage dish from the Shan people of Northern Thailand and Mynamar, Lynnette made squash and potatoes simmered in olive oils with both vegetables coming from our weekly CSA allotment. The dinner and subsequent conversations and disagreements (these are close friends and we have differing views on a wide variety of topics) lasted from just after 6 PM to just before 11.

It was immediately obvious that our friends favor oil, gas and coal as fuels. They don't think biofuels, solar energy, wind power, geothermal or tidal energy are economically feasible. They would approve of nuclear energy with appropriate precautions (avoiding building nuclear power plants on known earthquake faults or in areas prone to tidal waves comes to mind).

I think we haven't put enough time, money or brainpower into developing alternative energy sources and urgently need to do so. The political will to accomplish this seems lacking and our faltering, argumentative Congress, polarized as it currently is, hasn't helped the situation.

I certainly agree that subsidizing the growth of corn to be converted into ethanol isn't the way to go. And Brazil, despite its exceedingly osuccessful and sustainable biofuels program, isn't going to be able to supply enough ethanol to fuel the rest of the world.

Mount Saint Helen's in a quiet mood

Our friends said one volcano can add enough greenhouse gas (GHG) to make all our cars' polluting, to mix a metaphor, seem a drop in the bucket.

I don't disagree that the rare volcanic eruption can be catastrophic in this sense as in others (local loss of life and property among them). We've visited Mount Saint Helens (I strongly suggest reading Tim McNulty's 1998 retrospective on the explosion; just Google his name and add that of the mountain).

He makes the point that in this natural disaster, as opposed to industrial clear-cutting, damage was variable, trees, animals and insect survived and the area has come back strongly. I liked the line, "The ecosystem has been through this before."

Yet adding our dollop of pollution is not natural; it may tip us over an edge.

So I am in favor of the pursuit of alternative sources of energy. These may vary from country to country or within a country as the local winds, tides & solar-project possibilities permit.

But it's time and very nearly past time.

More on the heatwave and its consequences.

Thursday, September 1st, 2011

Here's one way to cool off

This morning I read in the New York Times Breaking News that comes to my Kindle that NYC has recently seen an unprecedented number of heat-related deaths. The age range of the victims varied considerably; youngsters, a 45-year-old  woman and some elderly folk all were struck down. Today I'd like to concentrate on older adults.

You may or may not believe in global warming (I certainly do) and, if you do, whether humans are making a significant contribution to it. But in the meantime we seem to be experiencing a hot patch and we have to cope with that.

I got up fairly early, took Yoda, my Tibetan terrier, to Whole Foods to buy a sack of his dog food and then took him for a walk. All in 72 to 75 degrees on a day that will later see a 95+ degree peak temperature. And this is in Colorado at 5,200 feet elevation. I checked out temp predictions for Denver and for the mountains; the former will be just under 100 degrees later on today whereas those areas at considerably higher elevation will stay in the 70s.

But agewise, I'm also in my 70s, as of April, and therefore read with interest the National Institute on Aging's paper titled "NIH tips for older adults to combat heat-related illnesses." The basic concepts are threefold: we lose some of our ability to adapt to heat as we get older; we are in a group that frequently has underlying diseases/conditions that fare poorly in hot weather; the meds our physicians use to treat those diseases sometimes limit our ability cope with the  heat.

I'll add a link to the article below, but will paraphrase some of their points and add my own spin.

Firstly some of the physiologic changes we experience as we age limit our ability to respond to elevated temperatures. Those include our cooling via sweating or , in some cases, our limited mobility and, in other cases, our mental responses or lack thereof. Additionally, our ability to vasodilate small blood vessels may be compromised.

Then we're experiencing, as a nation, an epidemic of obesity and concurrently those who exceed their weight goal by a large amount experience more heat-connected problems. I searched medical websites for the rationale and, if I were a teenager, would have said, "Duh!" The layer of adipose tissue the obese accumulate is the equivalent of wearing an insulted suit, something you wouldn't want to do in the heat of a summer day.

And then there are all those medications we take as we age. One article I found said older people take 2 to 6 prescribed drugs while also taking a number of OTC medications. Those drugs can directly alter our response to heat while potentially causing increased body temperature in a number of other ways, e.g., hypersensitivity reactions or the pharmacological action of the drug itself.

That helps

So if you're an older adult, avoid the heat of the day, get enough fluids and, if necessary, contact the Low Income Home Energy Assistance Program (through HHS) for help with home cooling.