(CNSNews.com) - Not every case of swine flu is related to the recent outbreak in Mexico.
Sometimes swine flu is just swine flu.
Case in point -- the April 17 issue of the federal Centers for Disease Control and Prevention’s (CDC) “Morbidity and Mortality Weekly Report” contains the following entry:
“A case of human infection with a novel swine influenza A virus was reported by the Iowa Department of Public Health during the week ending February 28, 2009.
The official federal health publication goes on to report: “A male aged 3 years was infected with a swine influenza A (H1N1) virus. An investigation revealed that the child had close contact with ill pigs. The child has fully recovered from the illness, and no additional cases were identified among the child’s contacts or other persons exposed to the ill pigs. This is the third human infection with swine influenza virus identified in the United States this influenza season.”
Is this Iowa case, then, part of the same swine flu outbreak that is affecting Mexico and elsewhere?
No, it’s not, according to the CDC.
“It does sound, on the surface, exactly like the swine virus we’re talking about now (in the Mexican outbreak), but it isn’t,” CDC spokesman Dave Daigle told CNSNews.com Wednesday.
“That case involved what we call the U.S. strain of swine influenza,” Daigle told CNSNews.com. “Those cases are rare. We’ve had about 12 cases over the last few years. Of those 12, 11 had direct or indirect contact with swine. The other one -- we just don’t have enough information about it to know for sure.”
Daigle underscored the fact that “we don’t see a lot of humans catching swine flu” from sick pigs.
“It is very rare in the U.S., but we do see some cases that circulate -- two to three a year -- and we usually can document contact with swine,” Daigle added.
Dr. Patricia Quinlisk, state epidemiologist and medical director of the Iowa Department of Public Health, said the case involving the 3-year-old isn’t even special, though the state did report it to the CDC.
“The one that the (child) had this year was a routine swine influenza strain that we’ve known about for a long time and we’ve seen somewhat regularly pop up in the United States,” Quinlisk said. “There was nothing unique about it.”
How do we know for sure that cases like the one in Iowa aren’t part of the Mexico strain? It was easy to determine, according to the CDC’s Daigle.
“We do a genetic sequencing on the isolates, and so the (strain) we’re seeing now (in the Mexico outbreak) does not have the U.S. strain of swine flu inside of it,” the CDC’s Daigle told CNSNews.com. “That’s what makes it so easy for us. (The Mexico strain) has European- and Asian-lineage swine flu in it. That’s the first time we’ve seen that in the U.S.”
The deadly strain in Mexico is unlike any other strain, he said.
“It has what we call ‘a genetic footprint’ from an avian, from a human and from European-and Asian-lineage swine,” Daigle added.
At the beginning of the Mexican outbreak, though, labs couldn’t even test for the type associated with the Mexican strain.
He explained: “Typically, you go to your doctor, and he gives you a rapid influenza test. If you have flu, it will come up A or B. That test then goes to a state health laboratory, and the state health laboratory will pin it down further. They can test for a whole range of influenza viruses.”
With the Mexico-associated outbreak, only one lab – a CDC-affiliated lab in Canada – was able to identify the current strain.
“In this case, when it was coming back to the state health labs, it was coming back as ‘Untypeable’ because it was something we haven’t seen,” Daigle said.
Labs have since been given the proper “reagents” to enable them to test for the Mexican strain.
In the case of the 3-year-old Iowa boy, Quinlist said health officials discovered his swine flu only because the state was testing for other reasons.
“The only way we picked up this one is that we have a special surveillance system, where when we get a certain percentage of people in Iowa that get the flu, we test them to see whether the virus and the vaccine match,” she told CNSNews.com.
“It’s not that we were looking for swine flu, it’s just that we happened to pick up this one, because we were testing the virus itself.”
The Iowa health officer said the incidence of people getting swine flu from infected pigs is somewhat rare – but it’s also routinue.
“To be honest, most of the time we never find them,” Quinlisk said. “Most the time people aren’t very sick, so they don’t go to the doctor, and even if they do go to the doctor, they say, ‘Oh you’ve got the flu.”
Moreover, most of the time, she said, avian flu really occurs only in birds, human flu only in people and swine flu only in swine.
“Every once in awhile, a person can get a swine flu, or a person can get an avian flu, but it usually doesn’t go very far because we are not the right host for it – it’s not meant for us. Maybe one person, or two people get sick, but it just stops, because it can’t replicate itself in humans.”
What makes the Mexican strain so dangerous, Daigle said, is that it is being transmitted from person to person – not pig to person.
“There’s the potential for a pandemic, because now we’re seeing a strain that we have not seen before, that has obviously gone – well, we have more to learn, but it is likely to have gone -- from swine to human, and now it is going from human to human,” he said. “That makes us very concerned.”
Ironically, Quinlisk announced Wednesday afternoon that Iowa now has two bona fide reported cases of the Mexican strain of swine flu A(H1N1) in the state.