(CNSNews.com) - The earliest confirmed U.S. case in the current swine flu outbreak occurred in a California county on the Mexican border where almost 18 percent of the residents are not U.S. citizens.
The patient was a 9-year-old girl living in Imperial County, Calif., who became ill on March 28, according to the April 24 issue of Morbidity and Mortality Weekly Report (MMWR), a publication of the federal Centers for Disease Control and Prevention (CDC).
The CDC confirmed today that this remains the earliest case in the U.S. determined to have been caused by the swine flu virus responsible for the ongoing outbreak, although it is possible through subsequent research that earlier U.S. cases may eventually be discovered.
The earliest confirmed case in Mexico, according to the CDC, occurred on March 17, 11 days before the case in Imperial County.
The Imperial County girl, who eventually recovered, had a cough and a high fever on March 28, and on April 17 the CDC confirmed that the source of her illness was the A (H1N1) swine flu virus.
The girl’s 13-year-old cousin, who lived in the same Imperial County household, also had flu-like symptoms on March 25, but he was not tested for the virus that causes swine flu, according to the CDC. The girl’s brother also had flu-like symptoms on April 1, but he was also not tested.
In a telephone conference with reporters on Friday afternoon, Dr. Nancy Cox, chief of the CDC’s Influenza Division, discussed the March 28 California case that had been reported in the MMWR.
“You know I do think that trying to go backwards in understanding how this began is important and valuable,” said Cox. “Our focus right now is on the response, on learning what we need to know about how to reduce the health impact of the virus. So our attentions are pretty intensely focused in that way. We appreciate that others are looking back and researching. And I would say that as we do our investigations here in the U.S., we may find that there were cases earlier.
“You know we have very good seasonal influenza surveillance system, and we didn’t find viruses before the March 28 one,” said Cox. “It was actually through some of those systems that we did detect this unusual, atypical virus. I think you all heard that since December of 2005 through January 2009 there were 12 non-type-able or atypical influenza strains tested here that turned out to have this swine association in terms of the nomenclature at that time.
“So, I think that we don’t know for sure that that was the first case here in the U.S., but I think the story going backward is important to understand. But our priority is going forward and focusing on response.”
Later in the telephone conference, Dr Cox said: “Basically, the first reported [U.S.] case with this sequence, etcetera, was from California.”
The April 24 issue of the MMWR said that 11 of the 12 other swine flu viruses identified by the CDC from December 2005 through January 2009 occurred in people who had had contact with pigs, while the source of the 12th virus was not determined.
“In the past, CDC has received reports of approximately one human swine influenza virus infection every 1-2 years in the United States,” said the MMWR. “However, during December 2005-January 2009, 12 cases of human infection with swine influenza were reported; five of these 12 cases occurred in patients who had direct exposure to pigs, six in patients reported being near pigs, and the exposure in one case was unknown."
The April 24 issue of the CDC’s Morbidity and Mortality Report also provided details about two initial U.S. cases in current swine flu outbreak, both of which occured in California counties that border Mexico. The first was the 9-year-old girl in Imperial County, who got sick on March 28, and the second was a 10-year-old boy in San Diego County, who got sick on Mar. 30.
“On March 28, 2009, she had onset of cough and fever (104.3°F [40.2°C]),” the MMWR reported. “She was taken to an outpatient facility that was participating in an influenza surveillance project, treated with amoxicillin/clavulanate potassium and an antihistamine, and has since recovered uneventfully.”
“The child had not received influenza vaccine during this influenza season,” said the MMWR. “The patient and her parents reported no exposure to pigs, although the girl did attend an agricultural fair where pigs were exhibited approximately 4 weeks before illness onset. She reported that she did not see pigs at the fair and went only to the amusement section of the fair.
“The Imperial County Public Health Department and the California Department of Public Health are now conducting an investigation to determine possible sources of infection and to identify any additional human cases,” said the report. “The patient’s brother aged 13 years had influenza-like symptoms on April 1, 2009, and a male cousin aged 13 years living in the home had influenza-like symptoms on March 25, 2009, 3 days before onset of the patient’s symptoms. The brother and cousin were not tested for influenza at the time of their illnesses.”
According to an April 30 dispatch by the CDC’s MMWR, the first confirmed swine flu patient in Mexico “reported onset of illness (any symptom) on March 17,” only 11 days before the 9-year-old girl in Imperial County, Calif., became ill.
Imperial County sits directly on the U.S.-Mexico border. It is contiguous with San Diego County to the West, the Colorado River and the state of Arizona to the East, and Mexico to the South. The Mexican city of Mexicali sits on the Mexican side of the border just below the lush, irrigated Imperial Valley.
According to the Census Bureau’s American Community Survey for 2007, Imperial County had a total population of 161,867. Of these, 28,506—or 17.6 percent--were not U.S. citizens.
The 2005-2007 American Community Survey estimated that more than 21 percent of Imperial County resident age 25 or older had less than a 9th grade education.
The 9-year-old girl who came down with swine flu in Imperial County on March 28 was referred to by the CDC’s MMWR as “Patient B.” “Patient A,” the second earliest confirmed case of swine flu in the United States, turned up next door in San Diego County.
“Patient A” was a 10-year-old boy who experienced coughing, vomiting and fever on March 30, two days after “Patient B.” On April 14, the CDC determined that he had been infected with A (H1N1) swine flu.
Although “Patient A”—the 10-year-old boy in San Diego County--sought treatment for his symptoms two days after “Patient B”—the 9-year-old girl in Imperial County--the CDC received a specimen of the virus from “Patient A” three days before it received the specimen “Patient B.”
Like the girl in Imperial County, “Patient A” recovered from his illness.
“The patient had onset of fever, cough, and vomiting on March 30, 2009,” said the CDC’s report. “He was taken to an outpatient clinic, and a nasopharyngeal swab was collected for testing as part of a clinical study. The boy received symptomatic treatment, and all his symptoms resolved uneventfully within approximately 1 week.”
Other members of the boy’s family had also been ill but it was not determined that they had had swine flu.
“The patient’s mother had respiratory symptoms without fever in the first few days of April 2009, and a brother aged 8 years had a respiratory illness 2 weeks before illness onset in the patient and had a second illness with cough, fever, and rhinorrhea on April 11, 2009,” said the CDC. “However, no respiratory specimens were collected from either the mother or brother during their acute illnesses.”
The CDC said the boy’s family traveled to Texas shortly after the boy’s illness.
“Public health officials are conducting case and contact investigations to determine whether illness has occurred among other relatives and contacts in California, and during the family’s travel to Texas on April 3, 2009,” said the CDC report.
According to the Census Bureau’s American Community Survey for 2007, San Diego County has a total population of 2,974,859, and a non-citizen population of 372,608--or 12.5 percent.
The Census Bureau does not ask survey respondents whether or not they are legally present in the United States.