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The epidemic in Russia was first recorded between 21st to 27th of September 2010 in South Sakhalin and cases were recorded in Kazakhstan three weeks later (October 16-22, 2010) in the north-east territories at the border of Siberia and Ural. The same as in Russia epidemic in Kazakhstan spread westward and southward.
The epidemic in Kazakhstan had moderate levels of intensity and differed from territory to territory as in Russia. In Astana and the north-east the epidemic intensity was higher in terms of duration (8-10 weeks) and morbidity level (7.8 -4.7 %) than in the south and south-west of Kazakhstan (4 weeks, morbidity 0.9% and 1.4%). Epidemic duration in Siberia and Ural (7.8 and 7.5 weeks) and morbidity level (10.2% and 9.6%) were higher than in the South and Privolzskiy federal regions (5.8 weeks and 5.7%). Morbidity levels in Russian regions was higher than in Kazakhstan because morbidity among city dwellers is normally higher than among country people.
In Kazakhstan the distribution of influenza and ARVI patients cases by age structure showed differences to the number of cases in Russia. The number of children's cases (age < 14) was more than in Russia 65, 0% and 52, 4% respectively.
Among infected > 65 aged people was slightly different in Kazakhstan and Russia and approximately equal (1.7% and 1.9%). Lethality from laboratory-confirmed influenza was 3.2% in Russia. Among people died in this epidemic in Russia people at ages 18-53 was 78.8%, and > 65 aged people -2.4%. Risk factor of lethal outcome from influenza was chronic pathology along side with late pregnancy.
Epidemiology in Kazakhstan resembled to Russian epidemic in terms of its abnormally early beginning (usually in December-January), expression of monoaetiology, spread of the epidemic into all territories and the identification of the first cases among the adult population. A higher percentage of hospitalized people and lethal outcome were registered in this epidemic. The similarity of the epidemiology of the outbreak in borderline territories of the two countries was investigated.
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Analysis of weekly influenza and ARVI morbidity in RK showed that influenza epidemic A(H1N1) had started in the 42nd week (October 16-22, 2009) in the territory of Karaganda oblast (Table 1). By week 43 week (October 23-29, 2009) an increase in morbidity was observed in Astana and in the territories of Pavlodar, Eastern Kazakhstan, and Northern Kazakhstan and Kostanay oblasts Morbidity for this week, as compared to previous, in Astana, Eastern Kazakhstan and Kostanay oblasts increased in 3, 2, and 1, 5 time, accordingly. And in Pavlodar and Northern Kazakhstan oblasts too exceeded the control levels of morbidity.
Table 1. Involving sequence and border of A(H1N1) 2009 epidemics in the Republic of Kazakhstan
In the 44th week (from the 30thOctober to the 5thNovember) an increase in morbidity was observed in the territories of Almaty, Akmola and Kyzylorda oblasts. In the 45th week (from the 6th to the 12th November 2009) the population of Atyrau, Southern Kazakhstan and Western Kazakhstan oblasts was involved in epidemic. In week 45 (from 13th till 19th of November) the Almaty city, Mangystau and Aktobe oblasts also recorded their first cases. The final territory included in the epidemic was Zhambul oblast.
By this point a peak in the number of cases was already registered in the territories which were involved in the earlier stages of the epidemic. In 46th week (from 30th to 5th November 2009) a peak was observed in Astana, a week later in Pavlodar and then in Karaganda oblast. The next three weeks (47-52 weeks) from November 20 till December 10, 2009 morbidity peaks were registered in Almaty and in all other oblasts. On average the morbidity peak throughout the country was for a week from 27th of November till 3rd of December. The peak started very soon in Astana and Almaty (2 weeks) as well as in Mangystau and Zhambyl oblasts; in Eastern Kazakhstan and Northern Kazakhstan oblasts the peak was not observed until 6 weeks after the first cases, on average the peak was observed in the 4thweek after the beginning of morbidity increase in these territories (Table 2). Influenza and ARVI morbidity during the epidemic peak on average was 822.1 with extremes of 311.2 (Southern Kazakhstan oblast) and 1542.2 (Astana) cases per 100 thousand people.
Table 2. Time of peaks in influenza and ARVI morbidity in 2009-2010 epidemic in Kazakhstan territories
Epidemic morbidity increase in the Republic of Kazakhstan was first observed among adults aged 15-29 and 30-64. Subsequently, cases in children were also recorded. An epidemic peak (maximum influenza morbidity and ARVI during a single week) among the young people (ages 15-29) was observed one week earlier than in other age-specific groups.
The epidemic in Kazakhstan lasted for 11 weeks (from the 16th October to the 31st December 2009. The duration of the epidemic in separate territories on average was 6.7 weeks with extremes of 4 weeks in the South (Mangystau and Zhambyl oblasts), 8 weeks (Karagandy, Northern Kazakhstan, Almaty, Eastern Kazahstan, Kyzylorda and Southern Kazakhstan oblasts) and 10 weeks (Astana) (Table 3).
Table 3. Duration of influenza and ARVI morbidity during the 2009-2010 A(H1N1) epidemic in the territories of Kazakhstan
The mean value of influenza and ARVI morbidity rates per 100, 000 for the entire population was 3326.3 among adults -1362.9 for children aged 0-14 years old was 7952.6. The highest morbidity level during this epidemic was registered in Astana with 7800.5 cases, children aged 0-14 -22837.0 and older than 15 -3236.5 per 100 thousand people. The lowest level of morbidity were registered in the Southern oblasts of Kazakhstan; for example, in Zhambyl oblast the population morbidity was 932.6 including population older than 15 -456.7 and children aged 0-14 -2137.5 cases per 100 thousand people.
Children aged 5-14 consisted the greater part of the influenza infected population. The percentage of infected children was 37.8% in the whole territory of Kazakhstan and varied throughout the territories from 28.9% in Kyzylorda oblast to 47.8% in Western Kazakhstan oblast (Table 4). Also, influenza and ARVI infections in children aged 0-4 was 27.2% nationally with fluctuations from 21.0% in Eastern Kazakhstan to 33.9% in Mangystau oblast. Influenza infected persons aged 15-29 consisted 22.6% of the total infections, persons aged 30-64-10.7% and persons aged > 65 -1.7%.
Table 4. Age distribution of influenza and ARVI cases during the 2009-2010 epidemic in the territories of Kazakhstan
The percentage of hospitalized patients during the epidemic period from all influenza infected people averaged 2.9% throughout RK and fluctuated from 0.9% in Atyrau oblast to 7.5% in Almaty. The percentage of hospitalized patients from the whole population was 0.09%, and fluctuated from 0.02% in Atyrau and Aktobe oblasts to 0.2% and 0.4% in Almaty and Astana respectively. Cases with lethal outcome were registered in Eastern-Kazakhstan (5 cases) and Kostanay oblasts (1 case). The cause of the deaths was likely the delay in seeking to medical care. Among those lethal cases was one woman 38 weeks pregnant and a child aged 1 year.
During the virological study of patients in Kazakhstan during epidemic period 18 influenza viral strains were isolated and identified as influenza virus A1. Two of them were sent to St.-Petersburg to Research Institute of Influenza. According to the data of the RII laboratory of influenza evolutionary variance of Research Institute of Influenza these viruses A/Astana/818/09 and A/Astana/830/09 reacted only with antisera derived from the pandemic viral strain A/California/07/09 (H1N1). Consequently they belong to this subtype.
According to PCR-RT data in influenza and ARVI etiology agents of non-influenza ethiology increased After outbreak.