中國發佈的死亡率，毫不可靠! (一定要參看自由時報這篇報導: http://tw.myblog.yahoo.com/ccshsu-clement/article?mid=10766&prev=10769&next=10764&l=a&fid=83) 我將下列comment寄到ProMED digest (ISID發行的免費報導世界各地動植物傳染病狀況的，很有用newsletter) 負責人，但其主編回信寫了一大堆不相干的話，似乎是說我寄錯人了。我又再看到Medscape Daily Medical Newletter [http://www.medscape.com/viewarticle/804596?nlid=31385_1661&src=wnl_edit_dail&uac=131220CK] 報導同樣文章之後，再寫一篇回應如下。
*******************************
My understanding is that in China, they only test those
who developed pneumonia for the presence of H7N9 infection. And
those tested positive are counted as the infected, and used as the denominator
to figure out the "mortality rate". Those who are infected but
asymptomatic, or have minor symptoms were not even tested for the H7N9. So the denominator will be erroneously low in
number, and the mortality rate is erroneously "very high". No wonder 97.3% of those patients in this
report had findings consistent with pneumonia on chest radiography.
This
is not a matter of whether H7N9 infection has high mortality or not. The issue is how mortality rate of an infection
should be calculated.
Shouldn't
the mortality rate of H7N9 infection derived by the number of those who died
from H7N9 infection (the numerator), divided by the number of people who were
infected regardless of whether they developed pneumonia or not (the
denominator) ?
This
highly irregular, if not irresponsible, way of "enumerating the mortality
rate of H7N9 infection" was reported by two Taiwan epidemiologists who
were officially sent to visit Shanghai Health Bureau and two Infectious Disease
Hospitals for 4 days to understand the status of H7N9 infection the first-hand
in early part of April, this year. Their
report was on the first page of the Liberty Times, with their photo, after
their return to Taiwan.
Please
check it out with the health officials in charge in China. Some basic concepts
need to be clarified with them. I have
known from other sources that the medical management in China is still some
distance behind the US standard.
If
what those epidemiologists found after visiting Chinese health officials was
correct, I do have a question. Why these
Taiwanese epidemiologists voice was not heard? Whether Taiwan is a member country of WHO or
not, this is a matter that involves epidemics that know no boundary.
*******************************
WHO Says New Bird Strain Is 'One of Most Lethal' Flu Viruses
(Reuters) - A new bird flu strain that has killed 22 people in China is "one of the most lethal" of its kind and transmits more easily to humans than another strain that has killed hundreds since 2003, a World Health Organization (WHO) expert said on Wednesday.
The H7N9 flu has infected 108 people in China since it was first detected in March, according to the Geneva-based WHO.
Although it is not clear exactly how people are being infected, experts say they see no evidence so far of the most worrisome scenario - sustained transmission between people.
An international team of scientists led by the WHO and the Chinese government conducted a five-day investigation in China, but said they were no closer to determining whether the virus might become transmissible between people.
"The situation remains complex and difficult and evolving," said Keiji Fukuda, the WHO's assistant director-general for health security.
"When we look at influenza viruses, this is an unusually dangerous virus for humans," he said at a briefing.
Another bird flu strain - H5N1 - has killed 30 of the 45 people it infected in China between 2003 and 2013, and although the H7N9 strain in the current outbreak has a lower fatality rate to date, Fukuda said: "This is definitely one of the most lethal influenza viruses that we've seen so far."
Scientists who have analyzed genetic sequence data from samples from three H7N9 victims say the strain is a so-called "triple reassortant" virus with a mixture of genes from three other flu strains found in birds in Asia.
Recent pandemic viruses, including the H1N1 "swine flu" of 2009/2010, have been mixtures of mammal and bird flu - hybrids that are more likely to be milder because mammalian flu tends to make people less severely ill than bird flu.
Pure bird flu strains, such as the new H7N9 strain and the H5N1 flu, which has killed about 371 of 622 the people it has infected since 2003, are generally more deadly for people.
UNSETTLING
The team of experts, who began their investigation in China last week, said one problem in tracking H7N9 is the absence of visible illness in poultry.
Fukuda stressed that the team is still at the beginning of its investigation, and said that "we may just be seeing the most serious infections" at this point.
Based on the evidence, "this virus is more easily transmissible from poultry to humans than H5N1", he said.
Besides the initial cases of H7N9 in and around Shanghai, others have been detected in Beijing and five provinces. On Wednesday, Taiwan's Health Department said a businessman had contracted H7N9 while travelling in China and was in a serious condition in hospital.
Samples from chickens, ducks and pigeons from poultry markets have tested positive for H7N9, but those from migratory birds have not, suggesting that "the likely source of infection is poultry", said Nancy Cox, director of the influenza division at the U.S. Centers for Disease Control and Prevention.
John Oxford, a flu virologist at Queen Mary University of London, said the emergence of human H7N9 infections - a completely new strain in people - was "very, very unsettling".
"This virus seems to have been quietly spreading in chickens without anyone knowing about it," he told Reuters in London.
Flu experts say it is likely that more cases of human infection with H7N9 flu will emerge in the coming weeks and months, at least until the source of infection has been completely confirmed and effectively controlled.
Anne Kelso, the Melbourne-based director of the WHO Collaborating Centre for Reference and Research on Influenza said there has been a "dramatic slowdown of cases" in the commercial capital of Shanghai, which has recorded most of the deaths, something she described as "encouraging".
After Shanghai closed down its live poultry markets in early April, there was an almost immediate decline in new H7N9 cases, she said. "The evidence suggests that the closing of the live poultry markets was an effective way to reduce the risks."
Even so, the WHO's China representative, Michael O'Leary, issued figures last week showing that half of the patients analyzed had no known contact with poultry.
(Editing by Louise Ireland)
******************
H7N9 Influenza: Most Patients Critically Ill
Most of the 82 patients studied who developed H7N9 became critically ill and were epidemiologically unrelated, according to an analysis of data obtained from field investigations of cases that occurred in China before April 17, 2013. Human-to-human transmission between close contacts has not been confirmed but could not be ruled out in 2 families in an analysis by a group of researchers from China and the Centers for Disease Control and Prevention.
Qun Li, MD, from the Public Health Emergency Center in China, and colleagues present their findings in an article published online April 24 in the New England Journal of Medicine.
The researchers defined a confirmed case as one verified by H7N9 virus presence by positive real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR), viral isolation, or serologic testing. Close contacts were observed for 7 days. The investigators obtained throat swabs from symptomatic contacts and tested for the H7N9 virus by real-time RT-PCR.
Among the 82 confirmed cases, the median age was 63 years (range, 2 - 89 years): 38 cases (46%) occurred in patients aged 65 years or older and 2 (2%) in children younger than 5 years. Both children had clinically mild upper respiratory illness. Two suspected cases were also found.
Of the confirmed cases, 73% were male, and 84% were urban residents. Of the 71 patients with available data, 54 (76%) had underlying medical conditions. Cases were reported in 6 areas of China.
Eighty-one patients with confirmed disease (99%) were hospitalized and 17 (21%) confirmed cases, and a single suspected case died of acute respiratory distress syndrome or multiorgan failure. A total of 60 confirmed cases and 1 suspected case remained critically ill as of April 17; 4 patients were discharged from the hospital, and 1 child was never hospitalized.
Animal Exposure
Animal exposure data were available for 77 of the confirmed cases. Of these patients, 59 (77%) had recent animal exposure: 45 (76%) to chickens, 12 (20%) to ducks, and 4 (7%) to swine. The individuals had either worked at or visited a live animal market. These patients also reported exposure to pigeons, geese, quail, wild birds, pet birds, cats, and dogs. History of animal exposure was unclear for the remaining 5 patients, in whom investigations were still ongoing.
The researchers estimated the median incubation period was 6 days in 23 patients for whom detailed data were available.
Of the 1689 close contacts, 1251 completed the 7-day monitoring period. A few (19; 1.5%) developed respiratory symptoms, but they all tested negative for the H7N9 virus.
There were 2 family clusters in which human-to-human transmission could not be ruled out. In one, a brother and his father were in prolonged, close contact with the index case. The father and brother cared for the index case and ate meals together. The index case had contact with live poultry, but the father and brother did not.
In the other family, a father had suspected illness and his daughter had prolonged, close, unprotected contact with him. She was later confirmed to have H7N9 illness. The father had contact with live poultry, but the daughter had no contact with poultry or pigs.
The investigators had data regarding oseltamivir administration for 64 patients, of whom 41 (64%) received oseltamivir starting a median of 6 days after illness onset.
"Although the risk of human-to-human transmission of H7N9 virus appears to be low, the actual risk is currently unknown, and the Chinese national guidelines recommend implementing control measures, such as prompt isolation of the patient, active monitoring of close contacts, and implementation of standard, contact, and droplet precautions by health care personnel in hospitals," the authors write.
"In addition, national guidelines recommend that antiviral treatment with oseltamivir should be administered as soon as possible in patients with suspected or confirmed cases of H7N9 virus infection," they conclude.
The China–US Collaborative Program on Emerging and Re-emerging Infectious Diseases provided financial support to a number of individuals and institutions for travel and accommodation fees for fieldwork, attendance at an investigator meeting, equipment, and fees for manuscript preparation. Two researchers reported employment at Jiangsu Provincial Center for Disease Control and Prevention. Two researchers received consulting fees from and 2 researchers reported employment by the China–US Collaborative Program on Emerging and Re-emerging Infectious Diseases. Two researchers reported receiving fees for travel to major meetings for the past 3 years.
N Engl J Med. Published online April 24, 2013.
Confirmed: New H7N9 Bird Flu Comes From Chickens
By Kate Kelland
LONDON (Reuters) Apr 25 - Chinese scientists have confirmed for the first time that a new strain of bird flu that has killed 23 people in China has been transmitted to humans from chickens.
In a study published online today in the Lancet, the scientists echoed previous statements from the World Health Organization (WHO) and Chinese officials that there is as yet no evidence of human-to-human transmission of this virus.
The H7N9 strain has infected 109 people in China since it was first detected in March. The WHO warned on Wednesday that this strain is "one of the most lethal" flu viruses and is transmitted more easily than the H5N1 strain of bird flu, which has killed hundreds around the world since 2003.
Kwok-Yung Yuen of the University of Hong Kong, who led the study, said its findings that chickens in poultry markets were a source of human infections meant that controlling the disease in these places and in these birds should be a priority.
"Aggressive intervention to block further animal-to-person transmission in live poultry markets, as has previously been done in Hong Kong, should be considered," he said.
He added that temporary closure of live bird markets and comprehensive programs of surveillance, culling, biosecurity and segregation of different poultry species may also be needed "to halt evolution of the virus into a pandemic agent."
"The evidence ... suggests it is a pure poultry-to-human transmission and that controlling (infections in people) will therefore depend on controlling the epidemic in poultry," he said.
Yuen's findings do not mean all cases of human H7N9 infection come from chickens, or from poultry, but they do confirm chickens as one source.
The WHO has said 40% of people infected with H7N9 appear to have had no contact with poultry.
Other types of birds or mammals may be acting as so called "reservoirs" of the flu virus and investigators in China are working hard to try to find out.
CASE STUDIES
Yuen's team conducted detailed case studies on four H7N9 flu patients from Zhejiang, an eastern coastal province south of the commercial hub Shanghai.
All four patients had been exposed to poultry, either through their work or through visiting poultry markets.
To find out whether there was transmission of the virus from poultry to humans, the researchers took swabs from 20 chickens, four quails, five pigeons and 57 ducks, all from six markets likely to have been visited by the patients.
Two of the five pigeons and four of the 20 chickens tested positive for H7N9, but none of the ducks or quails.
After analyzing the genetic makeup of H7N9 virus in a sample isolated from one patient and comparing it to a sample from one of the chickens, the researchers said similarities suggest the virus is being transmitted directly to humans from poultry.
The team also checked more than 300 people who had had close contact with the four patients and found that none showed any symptoms of H7N9 infection within 14 days from the beginning of surveillance. This suggests the virus is not currently able to transmit between people, they said.
But they noted that previous genetic analysis shows H7N9 has already acquired some gene mutations that adapt it specifically to being more able to infect mammals - raising the risk that it could one day spread more easily between people.
"Further adaptation of the virus could lead to infections with less severe symptoms and more efficient person-to-person transmission," the scientists wrote.
Lancet 2013.
沒有留言:
張貼留言