Household Transmission of Pandemic (H1N1) 2009, San Antonio, Texas, USA, April–May 2009

Morgan, Oliver; Parks, Sharyn E.; Shim, Trudi; Blevins, Patricia; Lucas, Pauline; Sanchez, Roger; Walea, N.; Loustalot, Fleetwood; Duffy, Mark R.; Shim, Matthew J.; Guerra, Sandra; Guerra, Fernando; Mills, Gwen; Verani, Jennifer R.; Alsip, Bryan; Lindstrom, Stephen; Shu, Bo; Emery, Shannon; Cohen, Adam L.; Menon, Manoj; Fry, Alicia M.; Dawood, Fatimah S.; Fonseca, Vincent P.; Olsen, Sonja J.

doi:10.3201/eid1604.091658

Cited by 61 publications

(62 citation statements)

References 17 publications

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“…A similar distinction was made in [14,18], both of which made estimates of the secondary attack rates for acute respiratory infection similar to our estimate. Influenza A/H1N1 occasionally leads to mild self-limiting illness, and not all the confirmed index cases had ILI.…”

Section: Discussionsupporting

confidence: 84%

Oseltamivir for treatment and prevention of pandemic influenza A/H1N1 virus infection in households, Milwaukee, 2009

et al. 2010

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BackgroundDuring an influenza pandemic, a substantial proportion of transmission is thought to occur in households. We used data on influenza progression in individuals and their contacts collected by the City of Milwaukee Health Department (MHD) to study the transmission of pandemic influenza A/H1N1 virus in 362 households in Milwaukee, WI, and the effects of oseltamivir treatment and chemoprophylaxis.Methods135 households had chronological information on symptoms and oseltamivir usage for all household members. The effect of oseltamivir treatment and other factors on the household secondary attack rate was estimated using univariate and multivariate logistic regression with households as the unit of analysis. The effect of oseltamivir treatment and other factors on the individual secondary attack rate was estimated using univariate and multivariate logistic regression with individual household contacts as the unit of analysis, and a generalized estimating equations approach was used to fit the model to allow for clustering within households.ResultsOseltamivir index treatment on onset day or the following day (early treatment) was associated with a 42% reduction (OR: 0.58, 95% CI: 0.19, 1.73) in the odds of one or more secondary infections in a household and a 50% reduction (OR: 0.5, 95% CI: 0.17, 1.46) in the odds of a secondary infection in individual contacts. The confidence bounds are wide due to a small sample of households with early oseltamivir index usage - in 29 such households, 5 had a secondary attack. Younger household contacts were at higher risk of infection (OR: 2.79, 95% CI: 1.50-5.20).ConclusionsEarly oseltamivir treatment may be beneficial in preventing H1N1pdm influenza transmission; this may have relevance to future control measures for influenza pandemics. Larger randomized trials are needed to confirm this finding statistically.

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Section: Discussionsupporting

confidence: 84%

Oseltamivir for treatment and prevention of pandemic influenza A/H1N1 virus infection in households, Milwaukee, 2009

et al. 2010

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Section: Discussionmentioning

confidence: 99%

“…8,15,18,22–24 A 7% secondary attack rate among household contacts not taking antiviral prophylaxis 18 was reported for a May–June 2009 outbreak of pH1N1 in Kobe, Japan, although 92% of the index cases received antiviral treatment. 18 Household secondary-attack-rate estimates were 9% for influenza-like illness in a spring 2009 outbreak in Texas 24 and 6% for confirmed pH1N1 infection in an early summer 2009 outbreak in Hong Kong. 23 Two analyses of influenza-like illness among the household contacts of children involved in an outbreak of pH1N1 in a New York City school estimated secondary attack rates of 18% 15 and 11%, 22 which fall within the 4%–23% range for US households.…”

Section: Discussionmentioning

confidence: 99%

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The Effect of Age on Transmission of 2009 Pandemic Influenza A (H1N1) in a Camp and Associated Households

Sugimoto

Borse²,

Ta³

et al. 2011

Epidemiology

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Background A major portion of influenza disease burden during the 2009 pandemic was observed among young people. Methods We examined the effect of age on the transmission of influenza-like illness associated with the 2009 pandemic influenza A (H1N1) virus (pH1N1) for an April–May 2009 outbreak among youth-camp participants and household contacts in Washington State. Results An influenza-like illness attack rate of 51% was found among 96 camp participants. We observed a cabin secondary attack rate of 42% (95% confidence interval = 21%–66%) and a camp local reproductive number of 2.7 (1.7–4.1) for influenza-like illness among children (less than 18 years old). Among the 136 contacts in the 41 households with an influenza-like illness index case who attended the camp, the influenza-like illness secondary attack rate was 11% for children (5%–21%) and 4% for adults (2%–8%). The odds ratio for influenza-like illness among children versus adults was 3.1 (1.3–7.3). Conclusions The strong age effect, combined with the low number of susceptible children per household (1.2), plausibly explains the lower-than-expected household secondary attack rate for influenza-like illness, illustrating the importance of other venues where children congregate for sustaining community transmission. Quantifying the effects of age on pH1N1 transmission is important for informing effective intervention strategies.

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“…This interval was based on a serial interval (the number of days between symptom onset in the index case-patient and household contacts) of up to 9 days to identify secondary cases, given that shedding of seasonal influenza virus rarely lasts >8 days ( 7 , 19 ) and a median incubation period for seasonal influenza of ≈1.4 days ( 7 , 20 ). Secondary cases were not required to be laboratory confirmed.…”

Section: Methodsmentioning

confidence: 99%

Intrahousehold Transmission of Pandemic (H1N1) 2009 Virus, Victoria, Australia

Gemert

Hellard

McBryde

et al. 2011

Emerg. Infect. Dis.

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Household Transmission of Pandemic (H1N1) 2009, San Antonio, Texas, USA, April–May 2009

Abstract: Transmission rates were lower than those for seasonal influenza.

Cited by 61 publications

References 17 publications

Oseltamivir for treatment and prevention of pandemic influenza A/H1N1 virus infection in households, Milwaukee, 2009

Oseltamivir for treatment and prevention of pandemic influenza A/H1N1 virus infection in households, Milwaukee, 2009

The Effect of Age on Transmission of 2009 Pandemic Influenza A (H1N1) in a Camp and Associated Households

Intrahousehold Transmission of Pandemic (H1N1) 2009 Virus, Victoria, Australia

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