Dynamics of Puumala hantavirus outbreak in Black Sea Region, Turkey

Some of the hantavirus species in Euro-Asia cause haemorrhagic fever with renal syndrome (HFRS) in humans. The first documented human hantavirus infection in Turkey was diagnosed in 2009. This report describes the dynamics of the first hantavirus outbreak that emerged in humans in the Western Black Sea Region of Turkey.

All the suspected cases of hantavirus infection were admitted to the Infectious Diseases and Clinical Microbiology Department at the Zonguldak Bülent Ecevit University Hospital in Zonguldak, Turkey. The patients were carefully interviewed, examined and evaluated using routine laboratory tests and hantavirus diagnostic tools. Hantavirus-reactive antibodies (IgM and IgG) in serum samples were detected via enzyme immune assay (EIA) and immunofluorescence assay (IFA) in the acute and convalescence stages of the disease. The presence of hantavirus ribonucleic acid (RNA) was analysed via reverse transcription polymerase chain reaction (RT-PCR) in serum and urine samples. A focus reduction neutralization test (FRNT) was performed to confirm specific hantavirus serotypes. In addition, a case-control study was conducted to identify possible risk factors for hantavirus transmission in the outbreak area. A control group was composed of asymptomatic individuals who were seronegative for hantavirus IgM and IgG and living in the outbreak area.

A total of 55 suspected cases of hantavirus infection were admitted to the inpatient clinic between February and June of 2009. Twenty-four patients were diagnosed with acute HFRS via EIA or IFA. In 22 of the 24 infected patients, Puumala virus (PUUV) was identified as the causative hantavirus type by detecting IgM in the acute stage and an increase in the IgG level in follow-up serum samples. PUUV was also verified as the infecting agent by FRNT in two of the 24 cases. Among the 24 laboratory-confirmed HFRS cases, 21 (87.5%) were males and 3 (12.5%) were females, and the mean age was 45.92 years (standard deviation ± 16.90 years). Almost all these individuals were living in villages or rural areas. The 24 HFRS cases were matched with 26 healthy controls for statistical analyses and according to binary logistic regression analysis, and dealing with rodent control activities in gardens or in annexes of their homes (p = 0.021 and Odds ratio [OR] = 17.11) and being male (p = 0.019 and OR = 22.37) were detected as statistically significant risk factors for hantavirus infection. The most commonly observed clinical complaints were fatigue (95.8%), shivering (91.7%), fever (87.1%), headache (70.8%) and nausea (70.8%). Haemodialysis was required for four patients (16.7%). Except for the first case diagnosed with acute hantavirus infection, no patient died. The mean delay time to hospital admission from initiation of symptoms was 5.3 days, the mean duration of febrile days was 2.6 days, and the mean duration of hospital stay was 8.5 days.

Hantaviruses are circulating in Turkey and causing sporadic or epidemic infection in humans. Additional investigations are needed to better understand the dynamics of hantaviruses in this country.