멕시코에서 2009년 4월 28일~6월 31일 인플루엔자 감시체계에 의해 수집된 정보를 분석함.
6월 31일까지 63,479건의 influenza-like illness 보고됨. 6,945건(11%) influenza A H1N1으로 확정진단. 확정진단을 받은 사례 중 6407건(92%)은 외래환자. 475건(7%)은 생존, 63건(<1%)은 사망. 10세~39세의 감염자는 3922건(56%). 치명율은 J자 모양의 곡선(J-shaped curve)을 보임. 70세 이상 사망율은 10·3%로 고연령군에서 가장 위험이 높게 나왔음.
계절성 독감 백신을 접종 받은 사람들의 사망 위험이 낮게 나왔음.(OR 0·65 [95% CI 0·55—0·77]). ) 입원이 지연되거나(1·19 [1·11—1·28] per day) 만성 질환자((6·1 [2·37—15·99])의 경우에 사망 위험이 더 높게 나왔음.
신종플루 치명율을 낮추기 위한 핵심요인은 위험정보교환(Risk communication)과 병원의 대응체계(hospital preparedness)라고 볼 수 있음.
이번에 [랜싯]지에 발표된 유사한 역학조사 결과 외에도 지난 10월 Journal of the American Medical Association (JAMA)에도 실린 멕시코의 중증환자 역학조사 결과(참고 : 10월 13일자 식품/의약품 자료실에 올려 놓은 논문 Critically Ill Patients With 2009 Influenza A(H1N1) in Mexico)도 참고할 것.
[랜싯]의 연구 결과를 HealthDay News는 “노령층일수록 돼지독감 위험 높아”로 보도하였고, AFP통신은 “젊은층일수록 돼지독감 감염 잘 돼”로 보도하였는데… 동일한 연구결과를 서로 다른 측면에서 해석한 것으로 볼 수 있음.
[참고 : 멕시코의 2009 인플루엔자 A(H1N1) 중증환자]
멕시코의 6개 병원에서 3월 18일~6월 1일 신종플루 확정진단 및 가진단을 받은 사람은 899명이었으며, 그 중에서 58명은 중증으로 진행되었으며, 중증환자의 평균 연령은 44세였습니다.
대부분의 중증 환자들에게 항생제를 투여했으며, 54명은 인공호흡기에 의지하였고, 그 중 45명은 타미플루나 릴렌자 같은 항바이러스제를 처방하였습니다.
58명의 중증환자 중에서 24명 (41.4%)이 입원한 지 60일 이내에 사망했습니다. (24명 중 19명은 입원한 지 2주 내에 사망했습니다)
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The Lancet, Early Online Publication, 12 November 2009
Infection and death from influenza A H1N1 virus in Mexico: a retrospective analysis
Summary
Background
In April, 2009, the first cases of influenza A H1N1 were registered in Mexico and associated with an unexpected number of deaths. We report the timing and spread of H1N1 in cases, and explore protective and risk factors for infection, severe disease, and death.
Methods
We analysed information gathered by the influenza surveillance system from April 28 to July 31, 2009, for patients with influenza-like illness who attended clinics that were part of the Mexican Institute for Social Security network. We calculated odds ratios (ORs) to compare risks of testing positive for H1N1 in those with influenza-like illness at clinic visits, the risk of admission for laboratory-confirmed cases of H1N1, and of death for inpatients according to demographic characteristics, clinical symptoms, seasonal influenza vaccine status, and elapsed time from symptom onset to admission.
Findings
By July 31, 63 479 cases of influenza-like illness were reported; 6945 (11%) cases of H1N1 were confirmed, 6407 (92%) were outpatients, 475 (7%) were admitted and survived, and 63 (<1%) died. Those aged 10—39 years were most affected (3922 [56%]). Mortality rates showed a J-shaped curve, with greatest risk in those aged 70 years and older (10·3%). Risk of infection was lowered in those who had been vaccinated for seasonal influenza (OR 0·65 [95% CI 0·55—0·77]). Delayed admission (1·19 [1·11—1·28] per day) and presence of chronic diseases (6·1 [2·37—15·99]) were associated with increased risk of dying.
Interpretation
Risk communication and hospital preparedness are key factors to reduce mortality from H1N1 infection. Protective effects of seasonal influenza vaccination for the virus need to be investigated.
Funding
None.
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Older People at Greater Risk of Swine Flu Death
출처 : HealthDay Wed Nov 11, 11:48 pm ET
WEDNESDAY, Nov. 11 (HealthDay News) — A study of H1N1 swine flu in Mexico finds that while babies and people under the age of 40 are most likely to get sick, elderly people have the highest death rates.
The research, published online Nov. 11 in The Lancet, analyzed medical records of patients at clinics in the Mexican Institute for Social Security network, who became sick with flu-like illnesses between April 28 and July 31, 2009.
The researchers found 63,479 cases of flu-like illness. Of the 6,945 confirmed cases of H1N1 swine flu, about 1 percent (63 patients) died. Seven percent (475 patients) were admitted to the hospital and lived.
Of those aged 70 and older who got sick, 10.3 percent died. By contrast, 0.9 percent of those aged 20 to 29 died, the study authors noted.
The researchers found that the risk of infection fell by 35 percent in those who received vaccinations for seasonal flu. Chronic disease boosted the risk of death by six times.
Those who didn’t go to the hospital within four days after developing symptoms boosted their risk of death by 20 percent for each extra day they delayed a hospital visit.
Pregnant women made up 6 percent of the deaths in Mexico. That rate is a bit lower than in the United States (8 percent) over the same time period.
“In Mexico, all pregnant workers were sent home during the peak of the pandemic, which probably accounts for this difference,” Dr. Victor Borja-Aburto of the Mexican Institute for Social Security in Mexico City, and colleagues wrote.
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Youngest likeliest to be infected, swine flu study confirms
출처 : AFP Wed Nov 11, 7:10 pm ET
PARIS (AFP) – New data from Mexico, the epicentre of the swine flu pandemic, has confirmed that young people are most at risk of catching the A(H1N1) virus but elderly patients are most at risk of dying from it.
The study bolsters the belief that the pathogen is not as virulent as first feared but also stresses the need for caution, as a mutation into a more lethal form cannot be ruled out.
Epidemiologists led by Victor Borja-Aburto of the Mexican Institute for Social Security looked at data for 63,479 people who had been treated for flu-like symptoms in public clinics from the start of the scare in April until the end of July.
Of the 6,945 cases confirmed by tests as H1N1, 56 percent occurred among people between 10 and 39 years, an age group with a high risk of contact through social interaction.
There were far fewer cases among older patients, which suggests that people in this age group were exposed in the past to a cousin to swine flu and may have gained some immunity, the author say.
But when analysed for mortality, a “J-shaped curve” revealed a preponderance of deaths among the elderly.
Among patients aged between 60 and 69, the death rate was 5.7 percent, compared with only 0.9 percent among patients aged between 20 and 29 years.
The study adds to several previous analyses which suggest vaccination against seasonal flu provides a partial shield.
It also strengthens warnings that people with chronic underlying disease are especially vulnerable. Individuals in this category increased their risk of death sixfold.
As of November, 1, more than 199 countries had reported lab-confirmed cases of swine flu, according to a toll published by the World Health Organisation (WHO) last Friday. There have been more than 482,300 notified cases and at least 6,071 deaths.
But the real number of swine flu infections is likely to be very much higher as many countries have stopped counting individual cases, says the WHO.
In addition, the count does not include people who have only mild symptoms — or no symptoms at all — and thus do not bother seeing a doctor.
The mortality rate from swine flu has been variously estimated at between 0.2 and 1.23 percent, according to the country or region or social group that is analysed.
At its lower range, this estimate is akin to the death toll from ordinary, so-called seasonal flu, of around 0.1 percent.
But even the highest figure is still only half of that for the 1918 Spanish flu, where the mortality rate is estimated to have been at least 2.5 percent. Tens of millions of people were killed in that event.
“Some researchers believe, with the information available up to now, that the present H1N1 influenza virus will not cause a pandemic on the scale of those during the 20th century,” said the new study, published online on Thursday by The Lancet.
“This pandemic might not be the one we expected; however, the virus is evolving and the threat continues.”
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