Epidemic Situation

Influenza and ARI morbidity data

Clinical and epidemiological data show low influenza activity in Russia. Epidemic thresholds of morbidity for overall population (specific for each city) were not exceeded at any of 59 cities under surveillance. The nationwide ILI & ARI morbidity level registered this week was below the national baseline (66.5 per 10 000) by 10.8%.

Cumulative number of diagnosed influenza cases

Cumulative results of influenza diagnosis by different tests were submitted by 54 RBLs. According to these data as a result of investigation of 1799 patients the overall proportion of respiratory samples positive for influenza  virus was estimated as 2.6% including  0.2% for influenza A(H1N1)pdm09 virus, 1.8% for A(H3N2) virus, 0.06% for non subtyped influenza A virus and 0.5% for influenza B virus (table 4).

Influenza Virus Isolation

During the reported week (January 23 - 29. 2012) investigations on influenza virus isolation were conducted in 14 Regional Base Laboratories (RBLs) participating in influenza surveillance in collaboration with two WHO NICs of Russia. As a result of 228 clinical samples testing two influenza A(H3N2) viruses were isolated in Mockow and Vladivostok (Central and Far-Eastern Federal Districts) (table 1).

Influenza Virus Antigen Detection by Immunofluorescence Assay (IFA)

Clinical specimens from 1000 patients with ILI and ARI were investigated in 45 RBLs  by IFA for direct detection of antigens in clinical samples. A total of 18 (1.8%) influenza cases were detected including:

- 13 (1.3%) influenza A(H3N2) cases in 7 cities of 4 Federal Districts (Siberian, North-Western, Volga and Central),

- 5 (0.5%)  influenza B cases in 3 cities of Siberian and Central Federal Districts.

Non-influenza respiratory viruses caused 20.6% of all investigated ILI and ARI cases including 9.4%, 5.7% and 5.5% for parainfluenza, adeno- and RS-viruses, correspondingly (table 2).

Influenza Virus RNA Detection by RT-PCR

Clinical samples from SARI, ILI and ARI patients were investigated by RT-PCR in 50 RBLs.

Influenza A(H1N1)pdm09 virus was detected in 4 (0.5%) cases in 2 cities of Siberian and Central Federal Districts, 

influenza A(H3N2) virus was detected in 21 (4.3%) cases in 10 cities of 5 Federal Districts (Southern, North-Western, Far-Eastern, Volga and Central),

non subtyped Influenza A virus was detected in 1 (0.1%) case in North-Western FD,

influenza B virus was detected in 4 (0.4%) cases in 4 cities of  4 Federal Districts (Ural, Siberian, Far-Eastern and Central).

Rate of PCR diagnosis of other respiratory infections was estimated as 19.3% including parainfluenza in 6.1%, adenovirus infection in 3.6%, RSV infection in 9.6% (table 3). 

Conclusion

Influenza and ARI morbidity data. Clinical and epidemiological data show low influenza activity in Russia. Epidemic thresholds of morbidity for overall population (specific for each city) were not exceeded at any of 59 cities under surveillance. The nationwide ILI & ARI morbidity level registered this week was below the national baseline (66.5 per 10 000) by 10.8%.

Etiology of ILI & ARI morbidity. The overall proportion of respiratory samples tested positive for influenza by virus isolation, IFA and rRT-PCR was estimated as 2.6%, for parainfluenza, adenovirus and RSV in total - as 19.3% (PCR) and 20.6% (IFA).

Sentinel surveillance. Clinical samples from 30 SARI patients and 45 ILI/ARI patients were investigated, one influenza A(H3N2) associated SARI case was detected in Far-Eastern Federal District.