Identification of influenza A pandemic (H1N1) 2009 variants during the first 2009 influenza outbreak in Mexico City.
BACKGROUND
In March 2009, public health surveillance detected increased numbers of influenza-like illness presenting to hospitals in Mexico City. The aetiological agent was subsequently determined to be a novel influenza A (H1N1) triple reassortant, which has spread worldwide. As a consequence the World Health Organisation has declared the first Influenza pandemic of the 21st century.


OBJECTIVE
To describe clinically and molecularly the first outbreak of influenza A pH1N1 (2009) during 1-5 May to establish a baseline of epidemiological data for pH1N1. Also, to monitor for the emergence of antiviral resistance, and mutations affecting virulence and transmissibility.


METHODS
Samples were collected from 751 patients with influenza-like symptoms throughout Mexico City and were tested for influenza A pH1N1 (2009) using real-time PCR. In the samples that were positive for influenza A pH1N1 (2009) fragments from the haemagglutinin (H1) and neuraminidase (N1) genes were sequenced.


RESULTS
A total of 203/751 (27%) patients were positive for the pandemic H1N1 (2009) virus (53% male and 47% female). The 0-12-year-old group was the most affected 85/751 (42%). Sequence analysis showed five new variants of the pandemic H1N1 (2009) virus for NA: G249E (GQ292900), M269I (GQ292892), Y274H (GQ292913), T332A (GQ292933), N344K (GQ292882), and four variants for HA: N461K (GQ293006), K505R (GQ292989), I435V (GQ292995), I527N (GQ292997).


CONCLUSIONS
We have provided a baseline of epidemiological data from the first outbreak of influenza A pH1N1 (2009) during 1-5 May in Mexico City. The sequencing of partial fragments of the HA and NA genes did not show the presence of previously described mutations affecting known sites of antiviral resistance in seasonal influenza A such as the H275Y (oseltamivir resistance), R293 or N295 etc.
Laboratorio de Medicina de Conservación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón s/n, Col. Casco de Santo, Mexico City 11340, Mexico. hzepeda@ipn.mx
Hector M
HM
Zepeda
Lizbeth
L
Perea-Araujo
Paola B
PB
Zarate-Segura
Joel A
JA
Vázquez-Pérez
Angel
A
Miliar-García
Claudio
C
Garibay-Orijel
Aarón
A
Domínguez-López
Jesús A
JA
Badillo-Corona
Eduardo
E
López-Orduña
Octavio P
OP
García-González
Ignacio
I
Villaseñor-Ruíz
Armando
A
Ahued-Ortega
Leopoldo
L
Aguilar-Faisal
Jorge
J
Bravo
Eleazar
E
Lara-Padilla
Ricardo J
RJ
García-Cavazos
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005260:Female; D014644:Genetic Variation; D005843:Geography; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D012367:RNA, Viral / Q000032:analysis
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; C483468:hemagglutinin, human influenza A virus; D009439:Neuraminidase