Evaluating influenza disease burden during the 2008-2009 and 2009-2010 influenza seasons in Mongolia

Nukiwa, Nao; Burmaa, Alexanderyn; Kamigaki, Taro; Darmaa, Badarchiin; Od, Jigjidsurengiin; Od, Ishiin; Gantsooj, Baataryn; Naranzul, T.; Tsatsral, Sosorbaramyn; Enkhbaatar, Luvsanbaldangiin; Tuul, Rentsengiin; Oshitani, Hitoshi; Nymadawa, Pagbajabyn

doi:10.5365/wpsar.2010.1.1.004

Cited by 12 publications

(17 citation statements)

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“…The ILI attack rate was highest among children aged 1–4 years, and this rate was almost the double of that for children aged 5–9 years. A similar age distribution of influenza cases was also observed in our previous study where we analyzed surveillance data from seasonal and pandemic influenza outbreaks [23], and a serological study of pandemic A(H1N1)2009 virus in Mongolia [29]. The high ILI attack rate noted among small children might be due to their susceptibility to influenza A(H3N2) virus, because there had been no major outbreak of influenza A(H3N2) virus since 2005/2006 season in Mongolia and the seasonal influenza vaccination was not routinely provided.…”

Section: Discussionsupporting

confidence: 84%

Influenza Transmission in a Community during a Seasonal Influenza A(H3N2) Outbreak (2010–2011) in Mongolia: A Community-Based Prospective Cohort Study

et al. 2012

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BackgroundKnowledge of how influenza viruses spread in a community is important for planning and implementation of effective interventions, including social distancing measures. Households and schools are implicated as the major sites for influenza virus transmission. However, the overall picture of community transmission is not well defined during actual outbreaks. We conducted a community-based prospective cohort study to describe the transmission characteristics of influenza in Mongolia.Methods and FindingsA total of 5,655 residents in 1,343 households were included in this cohort study. An active search for cases of influenza-like illness (ILI) was performed between October 2010 and April 2011. Data collected during a community outbreak of influenza A(H3N2) were analyzed. Total 282 ILI cases occurred during this period, and 73% of the subjects were aged <15 years. The highest attack rate (20.4%) was in those aged 1–4 years, whereas the attack rate in those aged 5–9 years was 10.8%. Fifty-one secondary cases occurred among 900 household contacts from 43 households (43 index cases), giving an overall crude household secondary attack rate (SAR) of 5.7%. SAR was significantly higher in younger household contacts (relative risk for those aged <1 year: 9.90, 1–4 years: 5.59, and 5–9 years: 6.43). We analyzed the transmission patterns among households and a community and repeated transmissions were detected between households, preschools, and schools. Children aged 1–4 years played an important role in influenza transmission in households and in the community at large. Working-age adults were also a source of influenza in households, whereas elderly cases (aged ≥65 years) had no link with household transmission.ConclusionsRepeated transmissions between households, preschools, and schools were observed during an influenza A(H3N2) outbreak period in Mongolia, where subjects aged 1–4 years played an important role in influenza transmission.

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Section: Discussionsupporting

confidence: 84%

Influenza Transmission in a Community during a Seasonal Influenza A(H3N2) Outbreak (2010–2011) in Mongolia: A Community-Based Prospective Cohort Study

et al. 2012

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“…Children <5 years old had the highest incidence of both ILI and sARI during the study period. A community‐based study in Mongolia also showed the highest incidence in young children . Similar results have been obtained in other countries .…”

Section: Discussionsupporting

confidence: 83%

Epidemiology and impact of influenza in Mongolia, 2007–2012

Burmaa

Kamigaki

Darmaa

et al. 2014

Influenza Resp Viruses

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BackgroundMongolia's Health Service began to conduct surveillance for influenza in the 1970s. This surveillance has become more comprehensive over time and now includes 155 sentinel sites in Mongolia. In this study, we analyzed the epidemiological characteristics and impact of influenza using data from influenza surveillance in Mongolia.Materials and methodsThe data were collected by the National Influenza Center, Mongolia (NIC). Incidence rates of influenza-like illness (ILI) and severe acute respiratory infections (sARI) were calculated as the proportion of the number of ILI and sARI cases to the total population in the studied areas. Nasopharyngeal samples were collected and tested using real-time reverse transcription polymerase chain reaction [(rt)-RT-PCR]. Selected samples negative for influenza were tested for other respiratory pathogens by multiplex rt-RT-PCR.ResultsAverages of 14·0 ILI and 0·8 sARI episodes per 100 population per year were observed during the five influenza seasons. The highest incidences of influenza associated with ILI and sARI were observed among children 0–4 years old. The number of ILI cases showed a clear seasonality, generally peaking between December and February. In contrast, sARI incidence peaked twice during each season. Influenza B was most prevalent during 2007–2008 and 2011–2012, influenza A (H3N2) during 2010–2011, seasonal A (H1N1) during 2008–2009, and A (H1N1) pdm09 during 2009–2010.ConclusionsAdditional data on the epidemiology and impact of influenza including socioeconomic impact and vaccine effectiveness are required to develop a national influenza control policy, including a vaccination strategy. Our results provide useful data for developing such a policy.

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“…In many northern hemisphere countries, there were smaller outbreaks between May 2009 and August 2009, followed by larger outbreaks between September 2009 and early 2010 15,16 . However, in Mongolia, no confirmed case of pandemic A (H1N1) 2009 occurred until October 12, 2009, despite an extensive search for cases with pandemic A (H1N1) 2009 17 . Mongolia has a low population density, and traveling between Mongolia and other countries and within the country occurs much less than in other Asian countries 18 .…”

Section: Discussionmentioning

confidence: 99%

Cumulative incidence of pandemic influenza A (H1N1) 2009 by a community‐based serological cohort study in Selenghe Province, Mongolia

Burmaa¹,

Tsatsral²,

Odagiri³

et al. 2012

Influenza Resp Viruses

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Please cite this paper as: Burmaa et al. (2012) Cumulative incidence of pandemic influenza A (H1N1) 2009 by a community‐based serological cohort study in Selenghe Province, Mongolia. Influenza and Other Respiratory Viruses 6(601), e97–e104. Background Large community outbreaks of pandemic A (H1N1) 2009 occurred between October and December 2009 in Mongolia. A serological study was conducted among the general population by testing paired sera collected before and after the first wave of pandemic in Selenghe province, Mongolia. None of the study participants had been vaccinated for pandemic A (H1N1) 2009 before the second samples were collected. Objective The objective of this study was to estimate cumulative incidence of pandemic A (H1N1) 2009 in different age‐groups of Selenghe province residents. Methods After informed consent was obtained from apparently healthy volunteers, the paired sera and background information were collected. Antibody titers were measured using hemagglutinin inhibition (HI) and microneutralization (MN) assays for A/California/07/2009pdm. A fourfold rise in antibody titers was regarded as the evidence of infection. Results The overall cumulative incidences in the study group for all ages were 28·8% (76/264) by HI, 35·2% (93/264) by MN, and 25·0% (66/264) by both HI and MN. Cumulative incidences of infection varied among age‐groups, with children aged 2–4 and 5–9 years having high cumulative incidence of infection. Overall cumulative incidences of infection in the whole population were estimated to be 23·0% (4946/21 460) by HI, 30·2% (6473/21 460) by MN, and 18·8% (4036/21 460) by both HI and MN. Conclusions This study indicates that about one‐fourth of the total population in Selenghe province was infected with pandemic A (H1N1) 2009 virus during the first wave of the pandemic.

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Evaluating influenza disease burden during the 2008-2009 and 2009-2010 influenza seasons in Mongolia

Cited by 12 publications

References 12 publications

Influenza Transmission in a Community during a Seasonal Influenza A(H3N2) Outbreak (2010–2011) in Mongolia: A Community-Based Prospective Cohort Study

Influenza Transmission in a Community during a Seasonal Influenza A(H3N2) Outbreak (2010–2011) in Mongolia: A Community-Based Prospective Cohort Study

Epidemiology and impact of influenza in Mongolia, 2007–2012

Cumulative incidence of pandemic influenza A (H1N1) 2009 by a community‐based serological cohort study in Selenghe Province, Mongolia

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