Objective To analyze impact of extreme low temperature and rainy weather on epidemic of infectious diseases in Nanning City and to provide a scientific basis of preventing and controlling infectious diseases caused by extreme weather events . Methods The data about incidences of respiratory tract infectious diseases ,enteric infectious diseases ,vector-borne infectious disea-ses ,natural foci of diseases from December 2007 to March 2008 and from December 2011 to April 2012 were analyzed by χ2 test . Results The incidence of respiratory tract infectious diseases were influenced greatest by extreme low temperature and rainy weather than other infectious diseases .The incidence of infectious diseases showed hysteresis effect of climate .Incidences of respira-tory tract infectious diseases ,enteric infectious diseases ,vector-borne infectious diseases ,natural foci of diseases during extreme low temperature and rainy weather were significantly higher than that during the same period of other years .And incidences of these were highest during the first 3 months of 2012 .Conclusion Extreme low temperature and rainy weather in Nanning City have im-pact on the incidence of infectious diseases ,which increased the incidence of infectious diseases at different degree .Ventilation and exposure clothes and quilts in the sun are not feasible during low temperature and rainy weather ,therefore health habits should be maximum emphasized when encountering extreme climate events .

Objective To compare the genetic barriers to development of primary mutations related to drug resistance to protease inhibitors (PI), nucleioside reverse transcriptase inhibitors ( NRTI ), and non-nucleioside reverse transcriptase inhibitors ( NNRTI ) among human immunodeficiency virus (HIV)-1 CRF01_AE, CRF07_BC, and CRF08_BC strains, and to understand the difference of varying patterns of drug resistance related mutations within these subtypes. Methods One hundred and ninety naive HIV-positive subjects from Nanning City and Liuzhou City, Guangxi Zhuang Autonomous Region, were recruited. Peripheral blood samples were collected from all participants. HIV-1 RNAs were extracted from plasma, and the pol regions were amplified and sequenced. Sequences were subjected to phylogenetic analysis to determine the subtypes of HIV-1 isolates. Nucleotide transitions and transversions were counted for each primary mutation in these sequences. According to the phenomena that transitions occur on average 2. 5 times frequently than transversions, each transition was scored as 1, and each transversion scored as 2. 5. The sum of the scores for a particular substitution was calculated, and this value was taken as the genetic barrier to development of this mutation. Then, the differences of genetic barriers among the subtypes were assessed by Kruskal-Wallis test and Nemenyi test. Results A total of 123 sequences of CRF01_AE,CRF07_BC and CRF08_BC strains were selected. CRF08_BC had a lower genetic barrier for T/S69Dsubstitution than CRF01_AE and CRF07_BC (χ2 =107. 501, P＜0.01), while CRF01_AE and CRF07_BC had lower genetic barriers for V118I and L210W substitution than CRF08_BC. In addition,CRF07_BC had a decreased genetic barrier for V106M compared with CRF01_AE and CRF08_BC.Conclusions In the presence of the same selective pressure, subtypes CRF01_AE and CRF07_BC may be more likely to develop V118I and L210W substitution than CRF08_BC. However, CRF08_BC may be more likely to develop T/S69D substitution than CRF01_AE and CRF07_BC. Meanwhile, CRF07_BC may be easier to develop V106M substitution than CRF01_AE and CRF08_BC.