the novel h1n1 influenza outbreak in april 2009 was unprecedented in several respects including the new virus , the season of origin ( spring , not late fall ) , and the cohort at risk for infection and death ( children and young adults , not infants and the elderly ) [ 14 ] .
the pandemic h1n1 2009 virus is currently the dominant influenza strain in most parts of the world [ 58 ] . by march 2010
, almost all countries had reported cases of infection and over 17,700 related deaths had been reported to the world health organization [ 912 ] .
posttraumatic stress disorder ( ptsd ) is a severe anxiety disorder that can result in severe disability across several domains of functioning [ 1315 ] .
ptsd usually occurs after exposure to any event that results in psychological trauma ; however , most people so exposed do not develop ptsd . to the best of our knowledge only 1 study has explored ptsd public during an epidemic .
that study reported the prevalence of probable ptsd cases was significantly higher in older people and in residents of severe acute respiratory syndrome ( sars)-prevalent regions , indicating that exposure degree and age might be significant predictors of ptsd .
the h1n1 influenza pandemic was unusual in that most people could not avoid being affected in some way , since television news , the internet and newspapers were filled with the reports of infection and death related to it .
the outbreak of h1n1 influenza caused not only extraordinary public health concerns but also tremendous psychological distress , particularly among youth , as they are among the most easily affected group during a global event .
universities are mass gathering places for youth , which has a high risk of spreading infectious diseases , particularly the 2009 pandemic influenza h1n1 .
the present study was designed to explore 2 research questions regarding stress symptoms among chinese university students during november - december 2009 .
second , are there predictors of distress in this sample ? regarding this question , it was hypothesized that greater overall stress symptom severity would be predicted by female gender , residence in north china ( where more influenza h1n1 cases were reported in china ) , lower university grade , having less knowledge about h1n1 influenza , not receiving the vaccine , having h1n1 influenza , having family members , friends or acquaintances having h1n1 influenza , contacting people infected with h1n1 influenza , and being afraid of h1n1 influenza .
the findings of this study will be important in planning for future outbreaks of emerging infectious diseases , especially in university students .
the subjects were recruited from 4 provinces of china , including heilongjiang , beijing , shanghai and sichuan during november - december 2009 .
the 4 provinces provide an adequate representation of socioeconomic status and geographical location of mainland china ( figure 1 ) . in north china ,
similarly , in south china , shanghai is a developed area , while sichuan is a developing .
university students attending various classes in one of the major classroom buildings on campus in the above 4 provinces were recruited in this study to complete a questionnaire designed by the primary authors .
the sample sizes from heilongjiang , beijing , shanghai and sichuan were 455 , 106 , 419 , and 102 , respectively .
demographics for the study samples from north china and south china are presented in table 1 .
the procedure for sampling classes was not random because availability of university students depended on instructor permission and scheduling considerations .
all participants completed a 17-item self - reported questionnaire , the ptsd checklist - civilian version ( pcl - c ) , which assesses the intrusive , avoidant , and arousal diagnostic and statistic manual of mental disorders - iv ptsd symptom clusters . the frequency of stress symptoms occurrence during the past 4 weeks was rated on a 5-point scale ranging from 1  not at all ,  through 3
 moderately ,  to 5  extremely .  this measure can be scored continuously by summing the values of each response or dichotomously using an algorithm that considers a corresponding response of  moderately  or greater as a symptom and follows the diagnostic and statistic manual of mental disorders - iv diagnostic rules requiring at least 1 symptom from the intrusive symptoms cluster , 3 symptoms from the avoidance symptoms cluster and 2 symptoms from the hyper - arousal symptoms . in the present study ,
the prevalence of symptoms consistent with a diagnosis of ptsd was ascertained using the recommended algorithm , whereas the relationship between participants characteristics and the burden of psychologic symptoms was ascertained using the pcl score as a continuous variable .
the difference of gender composition was analyzed with the  test while age was sampled with the two - sample t test .
reliability was assessed by using intraclass correlation coefficients and pearson correlation coefficients . the scores of ptsd reaction index were expressed as meansd . in preparation for regression analyses examining predictors of stress symptoms , correlations ( pearson r ) were calculated between hypothesized predictors and the pcl - c total score .
the possible predictors were area ( 0=in south china ; 1=in north china ) , gender ( 0=female;1=male ) , university grade ( 1=first year ; 2=second year ; 3= third year ; 4= fourth year ) , having knowledge about h1n1 influenza ( 1= a lot ; 2= some ; 3= a little ; 4= none ) , received vaccine ( 0= yes ; 1= no ) , having h1n1 influenza ( 1= yes , still in treatment ; 2= yes , but recovered ; 3= no ) , having family members , friends or acquaintances having h1n1 influenza ( 1= family members ; 2= friends ; 3= acquaintances ; 4= no ) , contacting people infected with h1n1 influenza ( 0= yes ; 1= no ) , being afraid of h1n1 influenza ( 1= very ; 2= somewhat ; 3= not ) .
the significantly correlated variables for the pcl - c total score were entered simultaneously as predictors in the regression analyses .
the subjects were recruited from 4 provinces of china , including heilongjiang , beijing , shanghai and sichuan during november - december 2009 .
the 4 provinces provide an adequate representation of socioeconomic status and geographical location of mainland china ( figure 1 ) . in north china ,
similarly , in south china , shanghai is a developed area , while sichuan is a developing .
university students attending various classes in one of the major classroom buildings on campus in the above 4 provinces were recruited in this study to complete a questionnaire designed by the primary authors .
the sample sizes from heilongjiang , beijing , shanghai and sichuan were 455 , 106 , 419 , and 102 , respectively .
demographics for the study samples from north china and south china are presented in table 1 .
the procedure for sampling classes was not random because availability of university students depended on instructor permission and scheduling considerations .
all participants completed a 17-item self - reported questionnaire , the ptsd checklist - civilian version ( pcl - c ) , which assesses the intrusive , avoidant , and arousal diagnostic and statistic manual of mental disorders - iv ptsd symptom clusters . the frequency of stress symptoms occurrence during the past 4 weeks was rated on a 5-point scale ranging from 1  not at all ,  through 3  moderately ,  to 5  extremely .
 this measure can be scored continuously by summing the values of each response or dichotomously using an algorithm that considers a corresponding response of  moderately  or greater as a symptom and follows the diagnostic and statistic manual of mental disorders - iv diagnostic rules requiring at least 1 symptom from the intrusive symptoms cluster , 3 symptoms from the avoidance symptoms cluster and 2 symptoms from the hyper - arousal symptoms . in the present study ,
the prevalence of symptoms consistent with a diagnosis of ptsd was ascertained using the recommended algorithm , whereas the relationship between participants characteristics and the burden of psychologic symptoms was ascertained using the pcl score as a continuous variable .
the difference of gender composition was analyzed with the  test while age was sampled with the two - sample t test .
the scores of ptsd reaction index were expressed as meansd . in preparation for regression analyses examining predictors of stress symptoms , correlations ( pearson r ) were calculated between hypothesized predictors and the pcl - c total score .
the possible predictors were area ( 0=in south china ; 1=in north china ) , gender ( 0=female;1=male ) , university grade ( 1=first year ; 2=second year ; 3= third year ; 4= fourth year ) , having knowledge about h1n1 influenza ( 1= a lot ; 2= some ; 3= a little ; 4= none ) , received vaccine ( 0= yes ; 1= no ) , having h1n1 influenza ( 1= yes , still in treatment ; 2= yes , but recovered ; 3= no ) , having family members , friends or acquaintances having h1n1 influenza ( 1= family members ; 2= friends ; 3= acquaintances ; 4= no ) , contacting people infected with h1n1 influenza ( 0= yes ; 1= no ) , being afraid of h1n1 influenza ( 1= very ; 2= somewhat ; 3= not ) . the significantly correlated variables for the pcl - c total score were entered simultaneously as predictors in the regression analyses .
there were 1082 people who participated in this study : 521 from south china and 561 from north china .
overall , the proportion of university students enrolled in this study who met symptomatic criteria for ptsd was 2% ( 22 students ) .
the mean pcl - c total score in the sample was 22.09 , with a standard deviation of 8.01 and scores ranging from 17 to 58 ( minimum possible score= 17 ; maximum= 58 ) . as exposure degree and age
have been shown to be related to the prevalence of ptsd in public , the potential predictors explored in this study include area , university year ( first year , second year , etc . ) , having h1n1 influenza , having family members , friends or acquaintances having h1n1 influenza , and contacting people infected with h1n1 influenza .
in addition , gender , having knowledge about h1n1 influenza , and being afraid of h1n1 influenza were also included .
the correlational analyses revealed a significant positive relationship between the pcl - c total score and area , and university grade ( p<0.01 , table 2 ) .
in addition , a negative relationship between the pcl - c total score and gender , having h1n1 influenza , having family members , friends or acquaintances having h1n1 influenza , and being afraid of h1n1 influenza was also found in this study ( p<0.01 , table 2 ) .
however , no correlation was found between pcl - c total score and having knowledge about h1n1 influenza , receiving the vaccine , and contacting people infected with h1n1 influenza ( p>0.05 , table 2 ) .
the regression analyses revealed that in north china , female gender , having h1n1 influenza , having family members , friends or acquaintances having h1n1 influenza , and being afraid of h1n1 influenza were significant predictors of the stress symptoms among chinese university students during the 2009 h1n1 influenza ( p<0.01 , table 3 ) .
children and young adults are the cohort at highest risk for h1n1 infection and death .
in addition , they are the most easily affected group during a global event . however , no information is available about the stress symptoms among youth during the 2009 h1n1 influenza pandemic .
the university environment has a high risk of spreading infectious diseases , particularly the 2009 pandemic influenza h1n1 , as it is a mass gathering place for youth .
to the best of our knowledge , the present study is the first to report stress symptoms among university students during the 2009 h1n1 influenza pandemic . in general , many students experienced a variety of stress reactions to the 2009 h1n1 influenza , and about 2.0% of students developed ptsd .
as predicted , in north china , female gender , having h1n1 influenza , having family members , friends or acquaintances having h1n1 influenza and being afraid of h1n1 influenza were significant predictors of stress symptoms in the current study .
this result is in line with the facts that stress symptoms are related to the degree of exposure to a stressful event .
in addition , as reported , females are in general 2.382.49 times more likely to develop lifetime ptsd than men after exposure to similar traumas . however ,
having knowledge about h1n1 influenza , receiving the vaccine , and contacting people infected h1n1 influenza were not predictors of the stress symptoms .
university students of higher grade had more stress symptoms , which was contrary to our previous prediction .
it is possible that university students of higher grades may be much more worried about the potential for 2009 h1n1 influenza to affect them directly when they begin their careers .
first , the participants were not recruited by random sampling procedures , and therefore there may be some bias in the sample that reduces the ability of the results to be generalized .
second , the measures of stress symptoms used in the present study may be vulnerable to various types of inherent bias as it is a self - report instrument .
however , the pcl - c has been widely proven to be a well validated measure of stress symptoms [ 1921 ] .
the current study supports other work indicating that individuals exposed to disasters only through media reports can also experience significant distress . despite this study s methodological shortcomings
, it extends research in this area by showing the stress symptoms and the significant predictors of the symptoms among chinese university students during the 2009 h1n1 influenza pandemic .
moreover , this study may contribute to understanding stress reactions among university students who were involved in the h1n1 influenza outbreak .
most importantly , the predictors found in this study may be extremely effective in defining the high risk group of the university students in similar influenza epidemics .
organizations will need to develop an integrated administrative and psychosocial response to the psychological challenges that are caused by future outbreaks of this nature .
in conclusion , in north china , female , having h1n1 influenza , having family members , friends , or others known having h1n1 influenza , and afraid of h1n1 influenza were significant predictors of the stress symptoms .
 summarybackgroundthe university environment poses a high risk of spreading infectious diseases , particularly the 2009 pandemic influenza h1n1 , as it is a mass gathering place for youth . 
 this study aimed to evaluate the predictors of stress symptoms among chinese university students during the 2009 h1n1 influenza pandemic.material/methodswe used a self - reported questionnaire , the ptsd ( posttraumatic stress disorder ) checklist - civilian version ( pcl - c ) to evaluate the stress symptoms among chinese university students from heilongjiang ( n=455 ) , beijing ( n=106 ) , shanghai ( n=419 ) and sichuan ( n=102 ) . 
 we then analyzed the predictors of stress symptoms.resultsthe proportion of university students enrolled in this study who met symptomatic criteria for ptsd was 2% ( 22 students ) . 
 the mean pcl - c total score in the sample was 22.098.01 . 
 the correlational analyses revealed a significant positive relationship between the pcl - c total score and area , and university grade ( p<0.01 ) . 
 moreover , a negative relationship was found between the pcl - c total score and gender , having h1n1 influenza , having family members , friends or acquaintances having h1n1 influenza , and being afraid of h1n1 influenza ( p<0.01 ) . 
 the regression analyses showed that in north china , female gender , having h1n1 influenza , having family members or acquaintances with h1n1 influenza , and being afraid of h1n1 influenza were significant predictors of the stress symptoms.conclusionsin north china , female gender , having h1n1 influenza , having family members , friends , or acquaintances with h1n1 influenza , and being afraid of h1n1 influenza were significant predictors of the stress symptoms . 
Background
Material and Methods
Samples and procedures
Measures
Statistical analysis
Results
Discussion
Conculsions