Household transmission of pandemic (H1N1) 2009, San Antonio, Texas, USA, April-May 2009.
To assess household transmission of pandemic (H1N1) 2009 in San Antonio, Texas, USA, during April 15-May 8, 2009, we investigated 77 households. The index case-patient was defined as the household member with the earliest onset date of symptoms of acute respiratory infection (ARI), influenza-like illness (ILI), or laboratory-confirmed pandemic (H1N1) 2009. Median interval between illness onset in index and secondary case-patients was 4 days (range 1-9 days); the index case-patient was likely to be < or =18 years of age (p = 0.034). The secondary attack rate was 4% for pandemic (H1N1) 2009, 9% for ILI, and 13% for ARI. The secondary attack rate was highest for children <5 years of age (8%-19%) and lowest for adults > or =50 years of age (4%-12%). Early in the outbreak, household transmission primarily occurred from children to other household members and was lower than the transmission rate for seasonal influenza.
Morgan
Oliver W
OW
Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Mailstop C12, Atlanta, GA 30333, USA. omorgan@cdc.gov
Parks
Sharyn
S
Shim
Trudi
T
Blevins
Patricia A
PA
Lucas
Pauline M
PM
Sanchez
Roger
R
Walea
Nancy
N
Loustalot
Fleetwood
F
Duffy
Mark R
MR
Shim
Matthew J
MJ
Guerra
Sandra
S
Guerra
Fernando
F
Mills
Gwen
G
Verani
Jennifer
J
Alsip
Bryan
B
Lindstrom
Stephen
S
Shu
Bo
B
Emery
Shannon
S
Cohen
Adam L
AL
Menon
Manoj
M
Fry
Alicia M
AM
Dawood
Fatimah
F
Fonseca
Vincent P
VP
Olsen
Sonja J
SJ
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000998:Antiviral Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005191:Family Characteristics; D005260:Female; D006801:Humans; D055256:Infectious Disease Incubation Period; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000188:drug therapy / Q000453:epidemiology / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D053139:Oseltamivir / Q000627:therapeutic use; D013781:Texas / Q000453:epidemiology; D055815:Young Adult
D000998:Antiviral Agents; D053139:Oseltamivir