Dear Sir,
In early 2013 (February), there was an emerging cluster of patients with respiratory diseases in China, which is known as novel H7N9 bird flu. At present, the new H7N9 bird flu becomes the global concern.Citation1–4 As an atypical influenza, there main clinical features are acute respiratory tract infection combining with additional non-respiratory presentations. The multiple organ involvement can be seen in many cases with new H7N9 bird flu.Citation1–4 The renal disorders are also mentioned.
In the previous scenarios of atypical influenza, H1N1 swine flu and H5N1 bird flu, the problem of renal disorder is well defined.Citation5,Citation6 Focusing on the present new H7N9 bird flu, Chen et al. reported in Lancet that the impaired renal function is a common laboratory finding.Citation7 However, Chen et al. did not propose for any pathogenesis of this observation.Citation7 In fact, the renal involvement might be due to the direct invasion of influenza virus to the kidney cell or the result of hemodynamic change in severe infected cases. The possibility of the direct infection to kidney cell of this new H7N9 virus can be supported by the fact that the virus can be well cultured in renal cell line.Citation7 According to the recent report by Gao et al.,Citation8 acute kidney injury is the third common complication of the new H7N9 bird flu (the first and second complications are respiratory distress syndrome and shock). Of interest, one-third of fatal cases had the acute renal injury.Citation8 Furthermore, the patients with underlying renal disease usually present severe H7N9 infection.Citation7,Citation8 Focusing on the BUN and creatinine levels, about 2.5 and 1.5 times normal values are observed, respectively.Citation8 The BUN-creatinine ratio can match with the pattern of acute renal failure.Citation8 Hence, the renal involvement is an important pathology in new H7N9 influenza that should be further studied.
As mentioned, there is a possibility that the new H7N9 influenza virus might directly cause the pathology at kidney. Focusing on the renal function test aberration in infected case, the increased levels of BUN and creatinine are observed in the patients with previous normal renal function.Citation9 It is presently advised that the renal function test should be monitored in management of the patients with new H7N9 infection. Focusing on a recent animal model study, the injection of the virus from a dead human case can result in the renal pathology in animal model.Citation10 This can imply the high possibility that the new H7N9 can directly invade the patients’ kidneys and cause the acute renal failure. However, due to the insufficient data on human death case autopsies, the confirmation on the existence of virus in kidney cannot be concluded.
Declaration of interest
The authors report no conflicts of interest.
References
- Centers for Disease Control and Prevention (CDC). Emergence of Avian Influenza A(H7N9) virus causing severe human illness – China, February–April 2013. MMWR Morb Mortal Wkly Rep. 2013;62(18):366–371
- Tang RB, Chen HL. An overview of the recent outbreaks of the avian-origin influenza A (H7N9) virus in the human. J Chin Med Assoc. 2013;76(5):245--248
- Kageyama T, Fujisaki S, Takashita E, et al. Genetic analysis of novel avian A(H7N9) influenza viruses isolated from patients in China, February to April 2013. Euro Surveill. 2013;18(15):20453
- Bertran K, Pérez-Ramírez E, Busquets N, et al. Pathogenesis and transmissibility of highly (H7N1) and low (H7N9) pathogenic avian influenza virus infection in red-legged partridge (Alectoris rufa). Vet Res. 2011;42(1):24
- Wiwanitkit V. Renal failure in swine flu: an appraisal from Thailand’s story. Ren Fail. 2010;32(1):150
- Wiwanitkit V. Renal insufficiency on presentation of bird flu infection: is it correlated to outcome? Clin Exp Nephrol. 2006;10(1):87–88
- Chen Y, Liang W, Yang S, et al. Human infections with the emerging avian influenza A H7N9 virus from wet market poultry: clinical analysis and characterization of viral genome. Lancet. 2013;381(9881):1916--1925
- Gao HN, Lu HZ, Cao B, et al. Clinical findings in 111 cases of influenza A (H7N9) virus infection. N Engl J Med. 2013;368(24):2277--2285
- Lu SH, Xi XH, Zheng YF, Cao Y, Liu XN, Lu HZ. Analysis of the clinical characteristics and treatment of two patients with avian influenza virus (H7N9). Biosci Trends. 2013;7(2):109–112
- H7N9 Bird Flu Virus May Be Human Transmissible. Available at: www.medicalnewstoday.com/articles/261022.php. Accessed July 1, 2013