Avian influenza viruses (AIVs) are negative-sense, single-stranded, enveloped RNA viruses which belongs to the influenza A genus of the Orthomyxoviridae family. Human influenza infections demonstrate a strongly seasonal pattern. However, whether H7N9 and H5N1 infections correlate with climate factors has not been examined.

LI Jing at the Institute of Microbiology, Chinese Academy of Sciences and other authors analyzed 350 cases of H7N9 infection and 47 cases of H5N1 infection. The spatial characteristics of these cases revealed that H5N1 infections mainly occurred in the South, Middle, and Northwest of China, while the occurrence of H7N9 was concentrated in coastal areas of East and South of China.

Aside from spatial-temporal characteristics, the most adaptive meteorological conditions for the occurrence of human infections by these two viral subtypes were different.

They found that H7N9 infections correlate with climate factors, especially temperature (TEM) and relative humidity (RHU), while H5N1 infections correlate with TEM and atmospheric pressure (PRS).

Hence, they propose a risky window (TEM 4–14 °C and RHU 65–95%) for H7N9 infection and (TEM 2–22 °C and PRS 980-1025 kPa) for H5N1 infection. The results represent the first step in determining the effects of climate factors on two different virus infections in China and provide warning guidelines for the future when provinces fall into the risky windows.

The live poultry markets (LPMs) act as a melting pot for a variety of viruses at a range of densities, and market networks with numerous trade connections should be closed down to avoid future avian influenza virus infections.

However, there is vast number of small-scale poultry producers, supplying a strong demand for live poultry in China. Consequently, permanently closing LPMs would likely prove unpopular, and therefore, their periodic closure may represent a more viable compromise.

The climate risk windows delineated in this study should be considered as important references for the guidance of any such solution. This strategy of metrological factor-based prediction can avoid large-scale live poultry culling and blindly closing live poultry markets to save a large amount of social resources.

These findings revealed integrated predictive meteorological factors rooted in statistic data that enable the establishment of preventive actions and precautionary measures against future outbreaks.

This work was published in Scientific Reports (www.nature.com/articles/srep18094) and supported by grants from National Program on Key Basic Research Project of China (973 Program), National Natural Science Foundation of China (NSFC), and the Chinese Academy of Sciences.Prof. LIU Wenjun is the corresponding author.

PCA and risk windows of H7N9 (A) and H5N1 (C) infection (Image by LI and LIU)

Key Words: influenza virus; climate factor

Contact:
Dr. LIU Wenjun

CAS Key Laboratory of Pathogenic Microbiology and Immunology，Institute Of Microbiology，Chinese Academy of Sciences，100101，Beijing, China
E-mail: liuwj@im.ac.cn