Monday, September 14, 2009


While pork producers and, belatedly, our USDA Secretary are busy waging a media war on "swine" flu, they may be a distraction to the troubling medical aspects of this infection.  To begin with, it doesn't attack the normal victims.
Seasonal flu kills predominantly the frail elderly. Researchers are trying to determine why the H1N1 swine flu virus, much like the Spanish Flu of 1918, is lethal to a portion of young people in good health. The reason may involve a person’s genetics, or simply taking a deep breath just as a nearby infected person sneezes.
“That’s a question we have to find the answer to,” said Nikki Shindo, a Geneva-based doctor leading the World Health Organization’s investigation of swine flu patients.
Underlying conditions that can intensify the effects of flu include respiratory illnesses, especially asthma, cardiovascular disease, diabetes, a suppressed immune system, and even pregnancy. About 25 percent to 50 percent of severe cases worldwide involve healthy young and middle-aged people like Robb, according to WHO Director-General Margaret Chan.
While the pandemic virus tightly latches onto cells in the upper respiratory tract like seasonal virus, it also attacks cells in the lungs, researchers at London’s Imperial College wrote in a study reported Sept. 10 in the journal Nature Biotechnology.
In severe cases, influenza can damage the capillaries surrounding the tiny grape-like sacs, known as alveoli, where gas is exchanged through the blood. Damaged alveoli can bleed, causing pulmonary hemorrhage and blood clots.
“What makes it go from the bronchus to the alveoli is the $64,000 question,” said John Nicholls, associate professor of pathology at the University of Hong Kong, who has studied how cells interact with viruses like the H5N1 bird flu strain and SARS. Previous bouts of flu, particularly caused by strains similar to the H1N1 virus, may give some protection, he said.
The U.S. Centers for Disease Control and Prevention is investigating the mechanisms for severe disease, Nancy Cox, director of the Atlanta-based agency’s flu division, told the meeting in San Francisco today.
“When the virus gets into the lower respiratory, it appears to replicate extremely well,” Cox said. “It’s really puzzling.”
Inflammatory chemicals are produced by the immune system to fight the infection and repair the damage. An over-exuberant response can worsen the effect by filling the lungs with fluid and cause permanent scarring that restricts the lungs.
The other problem is the relatively innocuous symptoms right up until crisis.
Can humans catch swine flu?
Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred. Most commonly, these cases occur in persons with direct exposure to pigs (e.g. children near pigs at a fair or workers in the swine industry). In addition, there have been documented cases of one person spreading swine flu to others. For example, an outbreak of apparent swine flu infection in pigs in Wisconsin in 1988 resulted in multiple human infections, and, although no community outbreak resulted, there was antibody evidence of virus transmission from the patient to health care workers who had close contact with the patient.
How common is swine flu infection in humans?
In the past, CDC received reports of approximately one human swine influenza virus infection every one to two years in the U.S., but from December 2005 through February 2009, 12 cases of human infection with swine influenza have been reported.
What are the symptoms of swine flu in humans?
The symptoms of swine flu in people are expected to be similar to the symptoms of regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea.
Can people catch swine flu from eating pork?
No. Swine influenza viruses are not transmitted by food. You can not get swine influenza from eating pork or pork products. Eating properly handled and cooked pork and pork products is safe. Cooking pork to an internal temperature of 160°F kills the swine flu virus as it does other bacteria and viruses.
How does swine flu spread?
Influenza viruses can be directly transmitted from pigs to people and from people to pigs. Human infection with flu viruses from pigs are most likely to occur when people are in close proximity to infected pigs, such as in pig barns and livestock exhibits housing pigs at fairs. Human-to-human transmission of swine flu can also occur. This is thought to occur in the same way as seasonal flu occurs in people, which is mainly person-to-person transmission through coughing or sneezing of people infected with the influenza virus. People may become infected by touching something with flu viruses on it and then touching their mouth or nose.
What do we know about human-to-human spread of swine flu?
In September 1988, a previously healthy 32-year-old pregnant woman was hospitalized for pneumonia and died 8 days later. A swine H1N1 flu virus was detected. Four days before getting sick, the patient visited a county fair swine exhibition where there was widespread influenza-like illness among the swine.

In follow-up studies, 76% of swine exhibitors tested had antibody evidence of swine flu infection but no serious illnesses were detected among this group. Additional studies suggest that one to three health care personnel who had contact with the patient developed mild influenza-like illnesses with antibody evidence of swine flu infection.
How can human infections with swine influenza be diagnosed?
To diagnose swine influenza A infection, a respiratory specimen would generally need to be collected within the first 4 to 5 days of illness (when an infected person is most likely to be shedding virus). However, some persons, especially children, may shed virus for 10 days or longer. Identification as a swine flu influenza A virus requires sending the specimen to CDC for laboratory testing. [More]
Meanwhile, pork producers are rightfully concerned about the name.   Unfortunately, that hog has escaped the barn I think.  (Notice the above came from government experts - the CDC - who are notably careful with nomenclature)
 Meanwhile, pork producers must worry about a fresh outbreak of the H1N1 flu virus. Though widely called swine flu, there is no evidence it is spread by pork. Nevertheless, the last outbreak hurt global pork demand and inspired China and other big importers to ban U.S. and Mexican pork. China already is raising more of its own pigs. [More]

As I have written before, this campaign is very late in forming. The swine flu label has been used epidemiologists for decades.  And this strain is not unrelated.
The new H1N1 strain is based primarily on an unusual virus that has been circulating widely in U.S. pigs since the 1990s. That "triple reassortant" flu is actually a combination of classic swine flu, a North American avian flu and a strain of human flu.

Somehow, a single pig became simultaneously infected with that virus and a pure swine flu strain found in pigs in Europe and Asia. The two strains swapped genetic material to produce the new H1N1 strain, which then began to infect humans.


That remains a mystery, and scientists will probably never know. Relatively few pigs engage in intercontinental travel, and those that do are strictly quarantined.

But there are theories. One is that a person in Asia became infected with the Eurasian swine flu, then traveled to North America and passed it along to a pig here that already had the triple reassortant virus. That would explain why the outbreak began in Mexico and the United States.


Yes. The extremely deadly 1918 Spanish flu was an H1N1 strain, and one of the strains of the seasonal flu is also an H1N1. But not all H1s and N1s are the same.

The H1 and N1 in the seasonal flu are both from humans. But new H1N1 is more virulent because most people never encountered it before, so they have no pre-existing immunity.


It doesn't seem to be deadlier than the seasonal flu, but it's hard to say for sure. Public health officials keep track of how many people have died from H1N1, but without reliable figures on total infections they don't know for sure what proportion of cases result in death.

Even if H1N1 is no deadlier than the seasonal flu, it will cause more deaths because it likely will infect more people.


Both viruses arose in late spring -- the tail end of the traditional flu season. And both appear to be most dangerous for healthy people in the prime of their lives instead of the very young and very old.

The 1918 flu is thought to have begun with a springtime wave that was followed by a more lethal wave in the fall. It ultimately killed about 50 million worldwide. [More]

The campaign to make H1N1 "the" term for this virus is making a difference, but I am becoming persuaded the greater danger is not to the pork industry.  The danger is to people.  I also suspect, but cannot find hard numbers to demonstrate, that a not-impossible pandemic could slow the global economy enough to stunt recovery in all meat demand.  Meat tends to be a discretionary purchase.

 The larger issue for me is the persistent conviction we can solve our problems by making others do stuff.  This is the guiding axiom behind "awareness" and "education" campaigns, and the fallback action plan for organizations seeking to buttress their reason for being.  Perhaps these efforts have proved fruitful in the past, but the sheer overuse of this technique has diluted its effectiveness, I fear.  (More on this in a later post)

1 comment:

Anonymous said...

Local media in our area have mostly gone to calling it H1N1. The reason I believe is because swine flu has given too many the false sense of security that they are in no danger if they just avoid pork or pigs.