Clinical and Epidemiologic Characteristics of Hospitalized Patients with 2009 H1N1 Influenza Infection

Objective. 2009 H1N1 virus is a new virus that was firstly detected in April 2009. This virus spreads from human to human and causes a worldwide disease. This paper aimed to review the clinical and epidemiological properties of patients with 2009 H1N1 influenza who were hospitalized and monitored at Eskisehir Osmangazi University Faculty of Medicine Hospital. Setting. A 1000-bed teaching hospital in Eskisehir, Turkey. Patients-Methods. Between 05 November 2009–01 February 2010, 106 patients with 2009 H1N1 influenza, who were hospitalized, were prospectively evaluated. Results. Out of 106 patients who were hospitalized and monitored, 99 (93.4%) had fever, 86 (81.1%) had cough, 48 (45.3%) had shortness of breath, 47 (44.3%) had sore throat, 38 (35.8%) had body pain, 30 (28.3%) had rhinorrhea, 17 (16%) had vomiting, 15 (14.2%) had headache, and 14 (13.2%) had diarrhea. When the patients were examined in terms of risk factors for severe disease, 83 (78.3%) patients had at least one risk factor. During clinical monitoring, pneumonia was the most frequent complication with a rate of 66%. While 47.2% of the patients were monitored in intensive care unit, 34% of them required mechanical ventilation support. Conclusion. Patients with 2009 H1N1 influenza, who were hospitalized and monitored, should be carefully monitored and treated.


Introduction
2009 H1N1 virus is a new virus that was firstly detected in April 2009. This virus spreads from human to human and causes a worldwide disease.
This study aimed to review the clinical and epidemiological properties of patients with 2009 H1N1 influenza who were hospitalized and monitored at Eskisehir Osmangazi University, Faculty of Medicine Hospital.

Materials and Methods
Between 05 November 2009-01 February 2010, 106 patients with 2009 H1N1 influenza, who were hospitalized and monitored at Eskisehir Osmangazi University, School of Medicine Hospital, were prospectively evaluated. The patients' demographics, complaints related to admission to hospital, duration of disease, physical examination findings, laboratory and radiological findings, name of the clinic where monitoring was performed, underlying diseases (age, chronic pulmonary, cardiovascular, renal, hepatic, hematologic, metabolic disease, neuromuscular disease, taking immunosuppressive therapy, pregnancy, obesity), complications developed, and prognosis were recorded in the patient recruitment forms prepared.
Respiratory distress, tachypnea, chest pain, confusion, persistent vomiting, worsening of general condition, and fever lasting more than three days were considered as a sign of serious illness, and these patients were hospitalized. Criteria for hospitalization in patients with, in addition, persistent hypoxemia, hemodynamic instability, sepsis and shock findings, if any of the planned admission to intensive care unit patients. In-patients, patients without evidence of improvement in spite of antiviral therapy and supportive, progressive pulmonary infiltrate, persistent hypoxemia (SpO2 < 92%), progressive hypercapnia, hemodynamic deterioration, signs of sepsis and shock in the case planned to be taken to intensive care unit patients.
Two thousand and nine H1N1 virus definitions by the World Health Organization, a national laboratory (Refik Saydam Hygiene Center) sent with the primary probe and positive controls, "Swine Influenza PCR Testing Kit," using "realtime reverse transcriptase polymerase chain reaction" was performed by analysis.
Statistical analysis, chisquare test, and Mann-Whitney U test were used.
In patients, duration of disease ranged between 3-34 days (10.9 ± 5.6 days on average) ( Figure 3). In 106 patients, who were hospitalized and monitored due to H1N1, virus identification was performed at National Influenza Laboratory with the analysis of real-time reverse transcriptase polymerase chain reaction. The complications, which occurred during clinical monitoring of the patients, are given in Table 2. In 16 of 70 cases of pneumonia, bacterial pneumonia was considered. Of these patients, blood and sputum cultures were negative. In Patients with suspected bacterial pneumonia, empiric treatment, were started according to guidelines.
Oseltamivir treatment was administered to all patients for 5 days. 8 of 106 patients (7.5%) with 2009 H1N1 influenza died. All deceased patients were those confirmed in terms  To be an underlying risk factor, there was no statistically significant relationship between the need of mechanical ventilation and death. Distribution per age for the deaths in patients with 2009 H1N1 influenza is given in Table 4.
All deceased patients had underlying disease that posed risk (Table 5).

Discussıon
2009 H1N1 virus causes a disease at levels varying from mild to severe. While no treatment is required for some patients, hospitalization is required for some of them [1].
Considering the conducted studies, 95% of the patients with 2009 H1N1 influenza consist of patients below 50 years [2,7]. In our patients with 2009 H1N1 influenza, who were hospitalized and monitored, mean age was detected to be 31.7 similar to the mean ages stated in different studies [8][9][10].
The following are considered to be risk factors for severe complications for 2009 H1N1 influenza infection: age above 65, age below 2, pregnancy, and chronic diseases [1]. In different studies, in patients with 2009 H1N1 influenza, underlying disease was reported to be at a rate of 68-73% [10,11]. When our patients were examined for underlying diseases which are possible risk factors, 78.3% of the patients had at least one risk factor. Chronic lung disease was detected in 17.9% of our patients, immunosuppression in 16%, neuromuscular disease in 12.3%, pregnancy in 11.3%, metabolic disease in 9.4%, cardiovascular disease in 6.6%, and obesity in 0.9%. While 11.3% of the patients consisted of those below 2 years, 8.5% of them comprised patients above 65 years. Pregnant women are under high risk in terms of morbidity and mortality associated with 2009 H1N1 influenza infection. In the studies conducted, abortus, birth defect, and preterm labor cases are reported [11][12][13][14][15][16][17][18]. 12 pregnant women were hospitalized and monitored in our hospital throughout pandemic period. No complication was seen except for pneumonia that developed in 3 patients. All patients recovered and discharged; no problem was experienced during their pregnancy followup.
The complications frequently reported for 2009 H1N1 influenza infection were pneumonia, bacterial coinfection, and exacerbation of underlying disease [19]. In our patients during clinical monitoring, pneumonia was the most frequent complication with a rate of 66%.
In the study conducted by Louie et al. [10], 31% of the patients with 2009 H1N1 influenza, who were hospitalized and monitored, are reported to require stay in intensive care, and 65% of them required mechanical ventilation. Whereas in the study conducted by Riquelme et al. [19], rate of stay in intensive care is reported to be 22%, and rate of patients who require mechanical ventilation is reported to be 68%. While 47.2% of our patients were monitored in intensive care unit, 34% of them required mechanical ventilation support. Contrary to the patients reported in studies of the literature, in our hospitalized patients with 2009 H1N1 influenza, it is observed that while indication of stay in intensive care is higher, requirement for mechanical ventilator is lower.
In our patients with 2009 H1N1 influenza, mortality rate is at similar rates with other studies in the literature [10,11]. In a study conducted by Jain et al., underlying disease is reported at a rate of 68% in patients who present a mortal course [11]. In our case series, all patients, who presented a mortal course, had underlying disease.

Conclusion
For 2009 H1N1 influenza infection, frequent presence of respiratory failure and requirement of mechanical ventilation in patients who needed hospitalization and developed pneumonia is notable. Unlike seasonal influenza, severe course, which is present also outside the risk groups, is noteworthy. Therefore, patients with 2009 H1N1 influenza, who were hospitalized and monitored, should be carefully monitored and treated.