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Assessing the impact of public health interventions on the transmission of pandemic H1N1 influenza a virus aboard a Peruvian navy ship.

ABSTRACT: BACKGROUND: Limited data exist on transmission dynamics and effectiveness of control measures for influenza in confined settings. OBJECTIVES: To investigate the transmission dynamics of a 2009 pandemic H1N1 influenza A outbreak aboard a Peruvian Navy ship and quantify the effectiveness of the implemented control measures. METHODS: We used surveillance data and a simple stochastic epidemic model to characterize and evaluate the effectiveness of control interventions implemented during an outbreak of 2009 pandemic H1N1 influenza A aboard a Peruvian Navy ship. RESULTS: The serological attack rate for the outbreak was 49·1%, with younger cadets and low-ranking officers at greater risk of infection than older, higher-ranking officers. Our transmission model yielded a good fit to the daily time series of new influenza cases by date of symptom onset. We estimated a reduction of 54·4% in the reproduction number during the period of intense control interventions. CONCLUSION: Our results indicate that the patient isolation strategy and other control measures put in place during the outbreak reduced the infectiousness of isolated individuals by 86·7%. Our findings support that early implementation of control interventions can limit the spread of influenza epidemics in confined settings.

SUBMITTER: Vera DM

PROVIDER: S-EPMC4181484 | biostudies-other | 2014 May

REPOSITORIES: biostudies-other

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Assessing the impact of public health interventions on the transmission of pandemic H1N1 influenza a virus aboard a Peruvian navy ship.

Vera Delphis M DM Hora Ricardo A RA Murillo Anarina A Wong Juan F JF Torre Armando J AJ Wang David D Boulay Darbi D Hancock Kathy K Katz Jacqueline M JM Ramos Mariana M Loayza Luis L Quispe Jose J Reaves Erik J EJ Bausch Daniel G DG Chowell Gerardo G Montgomery Joel M JM

Influenza and other respiratory viruses 20140210 3

<h4>Background</h4>Limited data exist on transmission dynamics and effectiveness of control measures for influenza in confined settings.<h4>Objectives</h4>To investigate the transmission dynamics of a 2009 pandemic H1N1 influenza A outbreak aboard a Peruvian Navy ship and quantify the effectiveness of the implemented control measures.<h4>Methods</h4>We used surveillance data and a simple stochastic epidemic model to characterize and evaluate the effectiveness of control interventions implemented ...[more]

PMID: 24506160

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Project description:Prior experience and the persisting threat of influenza pandemic indicate the need for global and local preparedness and public health response capacity. The pandemic of 2009 highlighted the importance of such planning and the value of prior efforts at all levels. Our review of the public health response to this pandemic in Pune, India, considers the challenges of integrating global and national strategies in local programmes and lessons learned for influenza pandemic preparedness.Global, national and local pandemic preparedness and response plans have been reviewed. In-depth interviews were undertaken with district health policy-makers and administrators who coordinated the pandemic response in Pune.In the absence of a comprehensive district-level pandemic preparedness plan, the response had to be improvised. Media reporting of the influenza pandemic and inaccurate information that was reported at times contributed to anxiety in the general public and to widespread fear and panic. Additional challenges included inadequate public health services and reluctance of private healthcare providers to treat people with flu-like symptoms. Policy-makers developed a response strategy that they referred to as the Pune plan, which relied on powers sanctioned by the Epidemic Act of 1897 and resources made available by the union health ministry, state health department and a government diagnostic laboratory in Pune.The World Health Organization's (WHO's) global strategy for pandemic control focuses on national planning, but state-level and local experience in a large nation like India shows how national planning may be adapted and implemented. The priority of local experience and requirements does not negate the need for higher level planning. It does, however, indicate the importance of local adaptability as an essential feature of the planning process. Experience and the implicit Pune plan that emerged are relevant for pandemic preparedness and other public health emergencies.

Project description:ObjectivesTo assess the risk of transmission of pandemic A/H1N1 2009 influenza (pandemic A/H1N1) from an infected high school group to other passengers on an airline flight and the effectiveness of screening and follow-up of exposed passengers.DesignRetrospective cohort investigation using a questionnaire administered to passengers and laboratory investigation of those with symptoms.SettingAuckland, New Zealand, with national and international follow-up of passengers.ParticipantsPassengers seated in the rear section of a Boeing 747-400 long haul flight that arrived on 25 April 2009, including a group of 24 students and teachers and 97 (out of 102) other passengers in the same section of the plane who agreed to be interviewed.Main outcome measuresLaboratory confirmed pandemic A/H1N1 infection in susceptible passengers within 3.2 days of arrival; sensitivity and specificity of influenza symptoms for confirmed infection; and completeness and timeliness of contact tracing.ResultsNine members of the school group were laboratory confirmed cases of pandemic A/H1N1 infection and had symptoms during the flight. Two other passengers developed confirmed pandemic A/H1N1 infection, 12 and 48 hours after the flight. They reported no other potential sources of infection. Their seating was within two rows of infected passengers, implying a risk of infection of about 3.5% for the 57 passengers in those rows. All but one of the confirmed pandemic A/H1N1 infected travellers reported cough, but more complex definitions of influenza cases had relatively low sensitivity. Rigorous follow-up by public health workers located 93% of passengers, but only 52% were contacted within 72 hours of arrival.ConclusionsA low but measurable risk of transmission of pandemic A/H1N1 exists during modern commercial air travel. This risk is concentrated close to infected passengers with symptoms. Follow-up and screening of exposed passengers is slow and difficult once they have left the airport.

Project description:BackgroundAs of June 11, 2009, a total of 17,855 probable or confirmed cases of 2009 pandemic influenza A (H1N1) had been reported in the United States. Risk factors for transmission remain largely uncharacterized. We characterize the risk factors and describe the transmission of the virus within households.MethodsProbable and confirmed cases of infection with the 2009 H1N1 virus in the United States were reported to the Centers for Disease Control and Prevention with the use of a standardized case form. We investigated transmission of infection in 216 households--including 216 index patients and their 600 household contacts--in which the index patient was the first case patient and complete information on symptoms and age was available for all household members.ResultsAn acute respiratory illness developed in 78 of 600 household contacts (13%). In 156 households (72% of the 216 households), an acute respiratory illness developed in none of the household contacts; in 46 households (21%), illness developed in one contact; and in 14 households (6%), illness developed in more than one contact. The proportion of household contacts in whom acute respiratory illness developed decreased with the size of the household, from 28% in two-member households to 9% in six-member households. Household contacts 18 years of age or younger were twice as susceptible as those 19 to 50 years of age (relative susceptibility, 1.96; Bayesian 95% credible interval, 1.05 to 3.78; P=0.005), and household contacts older than 50 years of age were less susceptible than those who were 19 to 50 years of age (relative susceptibility, 0.17; 95% credible interval, 0.02 to 0.92; P=0.03). Infectivity did not vary with age. The mean time between the onset of symptoms in a case patient and the onset of symptoms in the household contacts infected by that patient was 2.6 days (95% credible interval, 2.2 to 3.5).ConclusionsThe transmissibility of the 2009 H1N1 influenza virus in households is lower than that seen in past pandemics. Most transmissions occur soon before or after the onset of symptoms in a case patient.

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Assessing the impact of public health interventions on the transmission of pandemic H1N1 influenza a virus aboard a Peruvian navy ship.

Publications

Assessing the impact of public health interventions on the transmission of pandemic H1N1 influenza a virus aboard a Peruvian navy ship.

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