AVIAN INFLUENZA, HUMAN (140): ATYPICAL INFECTIONS
*************************************************
A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>
Date: Mon 4 Sep 2006
From: Stephen M. Apatow <s.m.apatow@humanitarian.net>
Comments on WHO Case Definitions and Atypical H5N1 Infections
----------------------------------------------------
In the context of the WHO case definitions for human infections with
influenza A(H5N1) virus, it appears that atypical infections continue
to be excluded from the potential clinical spectrum of challenge:
See:
<http://www.who.int/csr/disease/avian_influenza/guidelines/case_definition2006_08_29/en/index.html>
(29 Aug 2006), or ProMED-mail post "Avian influenza, human (133):
WHO case definitions" 20060830.2467.
WHO has defined a suspect case as: A person presenting with
unexplained acute lower respiratory illness with fever (>38 C [100.4
F]) and cough, shortness of breath or difficulty breathing. And one
or more of the following exposures in the 7 days prior to symptom
onset:
a. Close contact (within 1 metre) with a person (e.g. caring for,
speaking with, or touching) who is a suspected, probable, or
confirmed H5N1 case;
b. Exposure (e.g. handling, slaughtering, defeathering, butchering,
preparation for consumption) to poultry or wild birds or their
remains or to environments contaminated by their faeces in an area
where H5N1 infections in animals or humans have been suspected or
confirmed in the last month;
c. Consumption of raw or undercooked poultry products in an area
where H5N1 infections in animals or humans have been suspected or
confirmed in the last month;
d. Close contact with a confirmed H5N1 infected animal other than
poultry or wild birds (e.g. cat or pig);
e. Handling samples (animal or human) suspected of containing H5N1
virus in a laboratory or other setting.
However, the following references indicate that atypical infections
(encephalitis, diarrheal, gastrointestinal illness) are a serious
concern associated with outbreaks of avian influenza A subtype H5N1
worldwide (See:
<http://www.cdc.gov/ncidod/EID/vol10no7/pdfs/04-0415.pdf>: Emerging
Infectious Diseases, Vol. 10, No. 7, July 2004; and
<http://content.nejm.org/cgi/content/short/352/7/686>, NEJM, Volume
352:686-691, 17 Feb 2005, Number 7).
Furthermore, European researchers have reported what they call the
first evidence that low-pathogenic avian influenza (LPAI) viruses,
and not just highly pathogenic (HPAI) strains like H5N1, can infect
humans. The finding, in a study of Italian poultry workers, suggests
that avian influenza viruses have more chances than previously
suspected to mix with human influenza viruses, potentially creating
hybrids that could trigger a human influenza pandemic, according to a
report published online by the Journal of Infectious Diseases (See:
Low-pathogenic Avian Influenza (LPAI) Viruses Can Infect Humans
<http://www.cidrap.umn.edu/cidrap/content/influenza/avianflu/news/sep1305lpai.html>,
and ProMED-mail post "Avian influenza, human: LPAI susceptibility"
20050918.2759).
Diarrhea and the detection of viral RNA in most fecal samples tested
has been a frequent observation suggesting that H5N1 virus may
replicate in the human gastrointestinal tract. This raises the
question of whether human feces could be a source of transmission.
(See the Editorial Commentary on the Puzelli et al. paper by
Frederick Hayden and Alice Croisier in the journal of Infectious D
onlineiseases of 15 Oct 2005
<http://www.journals.uchicago.edu/JID/journal/issues/v192n8/35079/35079.web.pdf?erFrom=-1816478410120790350Guest>).
Examples of Asymptomatic Human Infection
----------------------------------------
(1) Four South Koreans were infected with the H5N1 strain of bird flu
in late 2003 and early 2004, but none of them developed any serious
illness, an official said 24 Feb 2006. (See:
<http://depts.washington.edu/einet/?a=printArticle&print=1564>).
(2) Three asymptomatic infections have been documented among close
contacts of confirmed cases in Viet Nam suggesting that milder H5N1
infections are occurring. Four persons who culled H5N1 infected birds
in Japan and 2 animal attendants caring for infected tigers in
Thailand also have antibodies to H5 virus. Asymptomatic infections
were also detected retrospectively in Hong Kong following the 1997
outbreak. (See:
<http://www.who.int/csr/disease/avian_influenza/H5N1%20Intercountry%20Assessment%20final.pdf>).
(3) On 9 Mar 2005 Vietnamese health authorities released information
about 2 such cases. Nguyen Tran Hien, director of the National
Institute for Hygiene and Epidemiology, confirmed that lab tests
showed that a 61-year-old woman from northern Thai Binh province had
contracted the H5N1 virus but was not showing any symptoms. (See:
<http://www.asianews.it/view.php?l=en&art=2732>).
(4) Two elderly relatives of people in Vietnam who died of bird
influenza have tested positive for the disease, despite having no
symptoms. Samples from another 7 cases that originally tested
negative in Viet Nam in January were re-tested in Tokyo and found to
carry the virus, according to the World Health Organization. (See:
<http://bmj.bmjjournals.com/cgi/content/extract/330/7492/616>).
(5) Dr Charoen Chuchottaworn, a bird-flu expert at the [Thai] Public
Health Ministry's Department of Medical Services, said doctors
concluded after reviewing the history of the past 2 cases that
bothvictims presented very mild symptoms of avian influenza and
neither had any physical contact with chickens or birds. (See:
<http://www.nationmultimedia.com/2005/12/02/national/index.php?news=national_19314560.html>.
While much has been made of the fulminant cases of presumed viral
pneumonia in 1918, Dr. Brundage's research indicates that the
majority of pneumonia cases, even in 1918, were either secondary
bacterial pneumonias following an influenza infection or mixed viral
and bacterial pneumonias. In the pre-antibiotic era, these cases of
bacterial pneumonia carried a very high mortality rate; however, with
appropriate antibiotic therapy, many such patients may be saved.
--
Stephen M. Apatow
<s.m.apatow@pathobiologics.org>
[There is still a deficit of comprehensive seroprevalence data to
establish the true frequency of subclinical infections and the
relevance of these sporadic accounts of atypical infections listed
above. For a discussion of this topic and an evaluation of some
published seroprevalence studies, the reader is referred to the
ProMED-mail posts archived as Avian influenza, human - Eurasia (41):
multicountry 20060130.0290 and Avian influenza, human - East Asia
(195): China 20051208.3538. - Mod.CP]
[see also:
Avian influenza, human (133): WHO case definitions 20060830.2467
Avian influenza, human - Eurasia (41): multicountry 20060130.0290
2005
----
Avian influenza, human - East Asia (195): China 20051208.3538
Avian influenza, human: LPAI susceptibility 20050918.2759]
........................cp/pg/lm
http://www.promedmail.org/pls/promed..._ID:1000,34290
*************************************************
A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>
Date: Mon 4 Sep 2006
From: Stephen M. Apatow <s.m.apatow@humanitarian.net>
Comments on WHO Case Definitions and Atypical H5N1 Infections
----------------------------------------------------
In the context of the WHO case definitions for human infections with
influenza A(H5N1) virus, it appears that atypical infections continue
to be excluded from the potential clinical spectrum of challenge:
See:
<http://www.who.int/csr/disease/avian_influenza/guidelines/case_definition2006_08_29/en/index.html>
(29 Aug 2006), or ProMED-mail post "Avian influenza, human (133):
WHO case definitions" 20060830.2467.
WHO has defined a suspect case as: A person presenting with
unexplained acute lower respiratory illness with fever (>38 C [100.4
F]) and cough, shortness of breath or difficulty breathing. And one
or more of the following exposures in the 7 days prior to symptom
onset:
a. Close contact (within 1 metre) with a person (e.g. caring for,
speaking with, or touching) who is a suspected, probable, or
confirmed H5N1 case;
b. Exposure (e.g. handling, slaughtering, defeathering, butchering,
preparation for consumption) to poultry or wild birds or their
remains or to environments contaminated by their faeces in an area
where H5N1 infections in animals or humans have been suspected or
confirmed in the last month;
c. Consumption of raw or undercooked poultry products in an area
where H5N1 infections in animals or humans have been suspected or
confirmed in the last month;
d. Close contact with a confirmed H5N1 infected animal other than
poultry or wild birds (e.g. cat or pig);
e. Handling samples (animal or human) suspected of containing H5N1
virus in a laboratory or other setting.
However, the following references indicate that atypical infections
(encephalitis, diarrheal, gastrointestinal illness) are a serious
concern associated with outbreaks of avian influenza A subtype H5N1
worldwide (See:
<http://www.cdc.gov/ncidod/EID/vol10no7/pdfs/04-0415.pdf>: Emerging
Infectious Diseases, Vol. 10, No. 7, July 2004; and
<http://content.nejm.org/cgi/content/short/352/7/686>, NEJM, Volume
352:686-691, 17 Feb 2005, Number 7).
Furthermore, European researchers have reported what they call the
first evidence that low-pathogenic avian influenza (LPAI) viruses,
and not just highly pathogenic (HPAI) strains like H5N1, can infect
humans. The finding, in a study of Italian poultry workers, suggests
that avian influenza viruses have more chances than previously
suspected to mix with human influenza viruses, potentially creating
hybrids that could trigger a human influenza pandemic, according to a
report published online by the Journal of Infectious Diseases (See:
Low-pathogenic Avian Influenza (LPAI) Viruses Can Infect Humans
<http://www.cidrap.umn.edu/cidrap/content/influenza/avianflu/news/sep1305lpai.html>,
and ProMED-mail post "Avian influenza, human: LPAI susceptibility"
20050918.2759).
Diarrhea and the detection of viral RNA in most fecal samples tested
has been a frequent observation suggesting that H5N1 virus may
replicate in the human gastrointestinal tract. This raises the
question of whether human feces could be a source of transmission.
(See the Editorial Commentary on the Puzelli et al. paper by
Frederick Hayden and Alice Croisier in the journal of Infectious D
onlineiseases of 15 Oct 2005
<http://www.journals.uchicago.edu/JID/journal/issues/v192n8/35079/35079.web.pdf?erFrom=-1816478410120790350Guest>).
Examples of Asymptomatic Human Infection
----------------------------------------
(1) Four South Koreans were infected with the H5N1 strain of bird flu
in late 2003 and early 2004, but none of them developed any serious
illness, an official said 24 Feb 2006. (See:
<http://depts.washington.edu/einet/?a=printArticle&print=1564>).
(2) Three asymptomatic infections have been documented among close
contacts of confirmed cases in Viet Nam suggesting that milder H5N1
infections are occurring. Four persons who culled H5N1 infected birds
in Japan and 2 animal attendants caring for infected tigers in
Thailand also have antibodies to H5 virus. Asymptomatic infections
were also detected retrospectively in Hong Kong following the 1997
outbreak. (See:
<http://www.who.int/csr/disease/avian_influenza/H5N1%20Intercountry%20Assessment%20final.pdf>).
(3) On 9 Mar 2005 Vietnamese health authorities released information
about 2 such cases. Nguyen Tran Hien, director of the National
Institute for Hygiene and Epidemiology, confirmed that lab tests
showed that a 61-year-old woman from northern Thai Binh province had
contracted the H5N1 virus but was not showing any symptoms. (See:
<http://www.asianews.it/view.php?l=en&art=2732>).
(4) Two elderly relatives of people in Vietnam who died of bird
influenza have tested positive for the disease, despite having no
symptoms. Samples from another 7 cases that originally tested
negative in Viet Nam in January were re-tested in Tokyo and found to
carry the virus, according to the World Health Organization. (See:
<http://bmj.bmjjournals.com/cgi/content/extract/330/7492/616>).
(5) Dr Charoen Chuchottaworn, a bird-flu expert at the [Thai] Public
Health Ministry's Department of Medical Services, said doctors
concluded after reviewing the history of the past 2 cases that
bothvictims presented very mild symptoms of avian influenza and
neither had any physical contact with chickens or birds. (See:
<http://www.nationmultimedia.com/2005/12/02/national/index.php?news=national_19314560.html>.
While much has been made of the fulminant cases of presumed viral
pneumonia in 1918, Dr. Brundage's research indicates that the
majority of pneumonia cases, even in 1918, were either secondary
bacterial pneumonias following an influenza infection or mixed viral
and bacterial pneumonias. In the pre-antibiotic era, these cases of
bacterial pneumonia carried a very high mortality rate; however, with
appropriate antibiotic therapy, many such patients may be saved.
--
Stephen M. Apatow
<s.m.apatow@pathobiologics.org>
[There is still a deficit of comprehensive seroprevalence data to
establish the true frequency of subclinical infections and the
relevance of these sporadic accounts of atypical infections listed
above. For a discussion of this topic and an evaluation of some
published seroprevalence studies, the reader is referred to the
ProMED-mail posts archived as Avian influenza, human - Eurasia (41):
multicountry 20060130.0290 and Avian influenza, human - East Asia
(195): China 20051208.3538. - Mod.CP]
[see also:
Avian influenza, human (133): WHO case definitions 20060830.2467
Avian influenza, human - Eurasia (41): multicountry 20060130.0290
2005
----
Avian influenza, human - East Asia (195): China 20051208.3538
Avian influenza, human: LPAI susceptibility 20050918.2759]
........................cp/pg/lm
http://www.promedmail.org/pls/promed..._ID:1000,34290
Comment