a pandemic caused by the new influenza a ( h1n1/09 ) virus resurged in march 2009 . this new virus is a quadruple - reassortant influenza a virus composed of human , swine and avian strains . clinical disease generally appears mild , but complications can occur , especially in those with underlying disease , pregnancy or patients on immunosuppression . our aim was to evaluate the clinical course in renal transplant recipients , as they are at increased risk of more severe h1n1 infection and mortality . the virus appears to have a predilection for infection of the lower respiratory tract , in some cases producing a severe pneumonia , acute respiratory distress syndrome or even multisystem organ failure . in germany , no influenza ( h1n1 ) strains circulating before december 2009 were reported to be resistant to neuraminidase inhibitors . we describe here three renal transplant patients with proven h1n1 infection . a 48-year - old woman with her third renal transplantation in 2009 experienced severe surgical complications post - transplantation with an application of a colostomy and a split skin graft . she was under double immunosuppression with tacrolimus and prednisolone at the time of admission , presenting at reduced clinical condition with headache and dysuria . creatinine was at 1.3 mg / dl ( mdrd egfr i.e. estimated gfr by utilizing the modification of diet in renal disease ( mdrd ) study equation 45 ml / min ) . antibiotic treatment was started and additional chest radiography on day 2 after admission revealed an interstitial pneumonia , but simultaneous testing of h1n1 in nasopharyngeal swabs was negative . the bronchoalveolar lavage fluid ( day 4 ) revealed the presence of cytomegalovirus , and intravenous ganciclovir was initiated . since day 4 , fever peaked to 39c and c - reactive protein ( crp ) to 4 mg / dl ( figure 1 ) , and she developed a productive cough . oseltamivir ( 75 mg b.i.d . ) led to a complete resolution of symptoms within 5 days . mdrd egfr was at 37 mg / dl ( creatinine 1.5 mg / dl ) . run of the curve of temperature and crp measures of patient 1 , patient 2 and patient 3 . arrows indicate positive and negative h1n1 pcr results . a 65-year - old woman transplanted in 2009 , with triple immunosuppression with tacrolimus , prednisolone and mycophenolic acid [ in reduced dosage ( 500 mg / b.i.d . ) because of recurrent urinary tract infections ] developed mild pulmonary symptoms with a non - productive cough 14 days prior to another urinary tract infection . renal function was stable ( creatinine 1.5 mg / dl , mdrd egfr 36 ml / min ) . the initial chest x - ray was negative , but she was admitted to the hospital for intravenous therapy of the urinary pseudomonas spp . another chest x - ray ( day 5 ) showed an infiltrate , while crp peaked to 14.8 mg / dl ( figure 1 ) . after positive nasopharyngeal swab h1n1 pcr ( day 6 ) , oseltamivir ( 75 mg / b.i.d . ) was initiated . creatinine increased to 1.8 mg / dl ( mdrd egfr 27 ml / min , day 15 ) . a 61-year - old male , transplanted in 1999 and suffering from chronic hepatitis c infection , received double immunosuppression consisting of tacrolimus and prednisolone . in july 2009 , he underwent nephrectomy of the left polycystic kidney due to a complicated cyst with ensuing multi - month hospital treatment because of postoperative complications with sepsis , an infected fistula of the pancreas and secondary wound healing with an application of a vacuum pump and consecutive antibiotic treatment ( vancomycin , ciprofloxacin ) . in november , the patient , still under antibiotic treatment , showed stable clinical condition and transplant function ( creatinine 2.4 mg / dl , mdrd egfr 28 ml / min ) . temperature then suddenly peaked to 39c ; crp was at 3.4 mg / dl ( figure 1 ) as he developed respiratory symptoms with cough and rhinitis . the chest x - ray revealed no infiltration , but an h1n1 pcr from nasopharyngeal swab was positive . antiviral therapy with oseltamivir 75 mg / b.i.d . led to a resolution of symptoms and a negative pcr control 1 week later ( figure 1 ) . the renal function remained stable ( creatinine 2.3 mg / dl , mdrd egfr 29 ml / min ) , without tacrolimus adjustment . a 48-year - old woman with her third renal transplantation in 2009 experienced severe surgical complications post - transplantation with an application of a colostomy and a split skin graft . she was under double immunosuppression with tacrolimus and prednisolone at the time of admission , presenting at reduced clinical condition with headache and dysuria . creatinine was at 1.3 mg / dl ( mdrd egfr i.e. estimated gfr by utilizing the modification of diet in renal disease ( mdrd ) study equation 45 ml / min ) . antibiotic treatment was started and additional chest radiography on day 2 after admission revealed an interstitial pneumonia , but simultaneous testing of h1n1 in nasopharyngeal swabs was negative . the bronchoalveolar lavage fluid ( day 4 ) revealed the presence of cytomegalovirus , and intravenous ganciclovir was initiated . since day 4 , fever peaked to 39c and c - reactive protein ( crp ) to 4 mg / dl ( figure 1 ) , and she developed a productive cough . oseltamivir ( 75 mg b.i.d . ) led to a complete resolution of symptoms within 5 days . mdrd egfr was at 37 mg / dl ( creatinine 1.5 mg / dl ) . run of the curve of temperature and crp measures of patient 1 , patient 2 and patient 3 . a 65-year - old woman transplanted in 2009 , with triple immunosuppression with tacrolimus , prednisolone and mycophenolic acid [ in reduced dosage ( 500 mg / b.i.d . ) because of recurrent urinary tract infections ] developed mild pulmonary symptoms with a non - productive cough 14 days prior to another urinary tract infection . renal function was stable ( creatinine 1.5 mg / dl , mdrd egfr 36 ml / min ) . the initial chest x - ray was negative , but she was admitted to the hospital for intravenous therapy of the urinary pseudomonas spp . another chest x - ray ( day 5 ) showed an infiltrate , while crp peaked to 14.8 mg / dl ( figure 1 ) . after positive nasopharyngeal swab h1n1 pcr ( day 6 ) , oseltamivir ( 75 mg / b.i.d . ) was initiated . creatinine increased to 1.8 mg / dl ( mdrd egfr 27 ml / min , day 15 ) . a 61-year - old male , transplanted in 1999 and suffering from chronic hepatitis c infection , received double immunosuppression consisting of tacrolimus and prednisolone . in july 2009 , he underwent nephrectomy of the left polycystic kidney due to a complicated cyst with ensuing multi - month hospital treatment because of postoperative complications with sepsis , an infected fistula of the pancreas and secondary wound healing with an application of a vacuum pump and consecutive antibiotic treatment ( vancomycin , ciprofloxacin ) . in november , the patient , still under antibiotic treatment , showed stable clinical condition and transplant function ( creatinine 2.4 mg / dl , mdrd egfr 28 ml / min ) . temperature then suddenly peaked to 39c ; crp was at 3.4 mg / dl ( figure 1 ) as he developed respiratory symptoms with cough and rhinitis . the chest x - ray revealed no infiltration , but an h1n1 pcr from nasopharyngeal swab was positive . antiviral therapy with oseltamivir 75 mg / b.i.d . led to a resolution of symptoms and a negative pcr control 1 week later ( figure 1 ) . the renal function remained stable ( creatinine 2.3 mg / dl , mdrd egfr 29 ml / min ) , without tacrolimus adjustment . influenza after solid organ transplantation appears to be more common among lung transplant recipients   but also causes significant morbidity among renal , liver and heart transplantation patients . influenza has also been associated with allograft rejection . to our knowledge , this is the first report on infections of renal transplant recipients with the new influenza a ( h1n1/09 ) virus . the three cases differ with respect to time after transplantation and to the immunosuppressive regimen . the first two cases are characterized by short time after grafting and reduced immunosuppression due to infectious complications . the third case had a longer time span after grafting with reduced immunosuppression and multiple infectious / surgical complications . the patients had not been vaccinated against the new influenza a. they were treated with oseltamivir in a standard dosage ( 75 mg / b.i.d . ) . onset of respiratory symptoms was fulminant in case 1 , but antiviral treatment was delayed and led to a rapid resolution of symptoms and a negative pcr result 4 days later . the second case exhibited mild respiratory symptoms for nearly 20 days before h1n1 pcr testing and antiviral therapy , which was effective within 1 week , despite fungal co - infection of the lung . both cases underline the benefit of antiviral treatment in the immunocompromised patient even when started late after infection . in the third case , fast symptom relief with clearance of the virus after oseltamivir treatment is concordant with other reports , but this observation is noteworthy and reassuring in immunosuppressed patients . overall , h1n1 infection showed an unexpectedly mild clinical course , similar to the general population . renal transplant function remained stable , while gfr decline in case 3 was most probably induced by drug interactions . the immunosuppressed renal transplant patient is prone to a severe h1n1 infection , but the cases described here showed a surprisingly mild clinical course despite respiratory co - infections . it is essential to test for influenza a ( h1n1/09 ) , as early administration of antiviral agents is recommended . our cases show that early antiviral therapy contributes to a fast resolution of respiratory symptoms and clearance of the virus . in addition , in our three cases , even delayed therapy was associated with a fast symptom relief . furthermore , oseltamivir in a standard dose proved effective without deteriorating transplant function or leading to adverse effects .