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Could Virulent Virus Be Harbinger of ‘New Flu'?

Could Virulent Virus Be Harbinger of ‘New Flu'? MORE THAN 1 MILLION chickens and other food fowl were slaughtered in Hong Kong, China—an event fraught with difficulty—late last month in an attempt to stem the spread of a new antigenic strain of influenza virus originating in birds. The virus emerged to infect at least 16 humans in Hong Kong and, as this issue of JAMA went to press, 4 of those infected had died (see also p 263). A major concern is the possibility that the new strain could be passed from human to human, which would herald the likelihood of a pandemic. While it is not clear how the virus is being transmitted, most of the cases so far seem to have occurred as a result of contact with chickens. "However, not all of them have been directly linked to exposure to birds. That's one of the questions we still have to answer," said a spokesman at the Centers for Disease Control and Prevention (CDC), Atlanta, Ga. But, pointed out the influenza expert, "Hong Kong is one big bird market." The virus has been identified as an H5N1 (hemagglutinin 5 neuraminidase 1) strain of influenza A. Because humans have not been exposed to this antigenic variant and the shift in the hemagglutinin antigen represents a major change, the possibility exists that, if the virus is transmitted through human contact, it could be the cause of a pandemic. Serum specimens are being taken to test for the presence of antibody to the virus. "There is no evidence so far that the infection has spread widely in the community or that there has been human-to-human transmission," said Daniel Lavanchy, MD, head of the World Health Organization (WHO) Division of Emerging and Other Communicable Diseases Surveillance and Control, who went to Hong Kong to assist in the investigation. CDC scientists who are also in Hong Kong agree. They are continuing their efforts to determine how those who have become ill were infected, whether other persons in Hong Kong and Southern China are infected with the virus, and whether there is evidence of person-to-person transmission. A CDC spokesperson who is in Hong Kong stresses that "so far there is no clear evidence that a major outbreak is likely." Began Last Spring The first person known to have become infected with the new strain—in May 1997 in Hong Kong—was a 3-year-old boy. The child died during an acute respiratory illness that subsequently was determined to be caused by H5N1 influenza type A. However, he died of Reye syndrome, apparently the result of being treated with aspirin. Subsequently, a serum specimen obtained from the physician who cared for the child has been identified as positive for the H5N1 virus. The physician is reported not to have developed any respiratory symptoms nor does he appear to have infected others, an indication that the virus may not be readily transmitted among humans and—even when it is transmitted—may not result in severe illness. Investigators from the CDC and the Hong Kong health department have reported that of 502 serum specimens from persons believed to have had contact with the initial patient, 9 were positive for the virus but only 1 person had mild symptoms of influenza. The second case involved a 2-year-old boy who developed fever in early November and was admitted to the hospital. Although he recovered, a nasopharyngeal aspirate taken during his hospitalization was positive for influenza A H5N1. The identification of the virus in both cases has since been confirmed independently by the WHO's Influenza Collaborating Center at the CDC, the National Influenza Center in Rotterdam, the Netherlands, and the National Institute for Medical Research in London, England. To date, there have been 7 other cases and 2 more deaths. Preparing for Worst Scenario Since there is no evidence that a pandemic is imminent, "the cases so far reported are not regarded as an emergency, but we are acting as if it were," said a CDC spokesperson. In short, the authorities are preparing for a worst-case scenario while hoping it does not eventuate. Initial steps have been taken to characterize the virus and develop a vaccine. One problem is that this virus is so virulent it kills the chick embryos on which it is cultivated for vaccine production. So scientists are trying to get a surrogate strain for H5N1, and the current strategy is to look for another chicken H5, said Edwin D. Kilbourne, MD, a research professor in the Department of Microbiology and Immunology at New York Medical College, Valhalla, NY. "There are many specimens in [researchers'] refrigerators that don't have the virulence of this particular strain," said Kilbourne, who is the developer of a technique for making recombinant influenza viruses that carry the desired antigenic strain to stimulate immunity while possessing the good growth characteristics needed for vaccine production. "Until a surrogate strain is selected, there isn't much I can do about making a recombinant," he said. "What I am pressing for is that we don't spend time looking for an exact match. Something is better than nothing." Two years ago, public health experts started to make plans to respond to an outbreak of pandemic influenza. At the time, they agreed that it was not a question of "if" a pandemic would occur—it was a matter of "when" (JAMA. 1996;275:179-180). What officials hope is that "when" has not already arrived. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA American Medical Association

Could Virulent Virus Be Harbinger of ‘New Flu'?

JAMA , Volume 279 (4) – Jan 28, 1998

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Publisher
American Medical Association
Copyright
Copyright © 1998 American Medical Association. All Rights Reserved.
ISSN
0098-7484
eISSN
1538-3598
DOI
10.1001/jama.279.4.259-JMN0128-3-1
Publisher site
See Article on Publisher Site

Abstract

MORE THAN 1 MILLION chickens and other food fowl were slaughtered in Hong Kong, China—an event fraught with difficulty—late last month in an attempt to stem the spread of a new antigenic strain of influenza virus originating in birds. The virus emerged to infect at least 16 humans in Hong Kong and, as this issue of JAMA went to press, 4 of those infected had died (see also p 263). A major concern is the possibility that the new strain could be passed from human to human, which would herald the likelihood of a pandemic. While it is not clear how the virus is being transmitted, most of the cases so far seem to have occurred as a result of contact with chickens. "However, not all of them have been directly linked to exposure to birds. That's one of the questions we still have to answer," said a spokesman at the Centers for Disease Control and Prevention (CDC), Atlanta, Ga. But, pointed out the influenza expert, "Hong Kong is one big bird market." The virus has been identified as an H5N1 (hemagglutinin 5 neuraminidase 1) strain of influenza A. Because humans have not been exposed to this antigenic variant and the shift in the hemagglutinin antigen represents a major change, the possibility exists that, if the virus is transmitted through human contact, it could be the cause of a pandemic. Serum specimens are being taken to test for the presence of antibody to the virus. "There is no evidence so far that the infection has spread widely in the community or that there has been human-to-human transmission," said Daniel Lavanchy, MD, head of the World Health Organization (WHO) Division of Emerging and Other Communicable Diseases Surveillance and Control, who went to Hong Kong to assist in the investigation. CDC scientists who are also in Hong Kong agree. They are continuing their efforts to determine how those who have become ill were infected, whether other persons in Hong Kong and Southern China are infected with the virus, and whether there is evidence of person-to-person transmission. A CDC spokesperson who is in Hong Kong stresses that "so far there is no clear evidence that a major outbreak is likely." Began Last Spring The first person known to have become infected with the new strain—in May 1997 in Hong Kong—was a 3-year-old boy. The child died during an acute respiratory illness that subsequently was determined to be caused by H5N1 influenza type A. However, he died of Reye syndrome, apparently the result of being treated with aspirin. Subsequently, a serum specimen obtained from the physician who cared for the child has been identified as positive for the H5N1 virus. The physician is reported not to have developed any respiratory symptoms nor does he appear to have infected others, an indication that the virus may not be readily transmitted among humans and—even when it is transmitted—may not result in severe illness. Investigators from the CDC and the Hong Kong health department have reported that of 502 serum specimens from persons believed to have had contact with the initial patient, 9 were positive for the virus but only 1 person had mild symptoms of influenza. The second case involved a 2-year-old boy who developed fever in early November and was admitted to the hospital. Although he recovered, a nasopharyngeal aspirate taken during his hospitalization was positive for influenza A H5N1. The identification of the virus in both cases has since been confirmed independently by the WHO's Influenza Collaborating Center at the CDC, the National Influenza Center in Rotterdam, the Netherlands, and the National Institute for Medical Research in London, England. To date, there have been 7 other cases and 2 more deaths. Preparing for Worst Scenario Since there is no evidence that a pandemic is imminent, "the cases so far reported are not regarded as an emergency, but we are acting as if it were," said a CDC spokesperson. In short, the authorities are preparing for a worst-case scenario while hoping it does not eventuate. Initial steps have been taken to characterize the virus and develop a vaccine. One problem is that this virus is so virulent it kills the chick embryos on which it is cultivated for vaccine production. So scientists are trying to get a surrogate strain for H5N1, and the current strategy is to look for another chicken H5, said Edwin D. Kilbourne, MD, a research professor in the Department of Microbiology and Immunology at New York Medical College, Valhalla, NY. "There are many specimens in [researchers'] refrigerators that don't have the virulence of this particular strain," said Kilbourne, who is the developer of a technique for making recombinant influenza viruses that carry the desired antigenic strain to stimulate immunity while possessing the good growth characteristics needed for vaccine production. "Until a surrogate strain is selected, there isn't much I can do about making a recombinant," he said. "What I am pressing for is that we don't spend time looking for an exact match. Something is better than nothing." Two years ago, public health experts started to make plans to respond to an outbreak of pandemic influenza. At the time, they agreed that it was not a question of "if" a pandemic would occur—it was a matter of "when" (JAMA. 1996;275:179-180). What officials hope is that "when" has not already arrived.

Journal

JAMAAmerican Medical Association

Published: Jan 28, 1998

Keywords: viruses

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