Malaria in Zhejiang Province, China, from 2005 to 2014
Am. J. Trop. Med. Hyg.
Hualiang Chen 0 1
Linong Yao 0 1
Lingling Zhang 0 1
Xuan Zhang 0 1
Qiaoyi Lu 0 1
Kegen Yu 0 1
Wei Ruan 0 1
0 for Disease Control and Prevention , Binsheng Road 3399, Hangzhou 310051 , China
1 Zhejiang Provincial Center for Disease Control and Prevention , Hangzhou , China
To summarize the changing epidemiological characteristics of malaria in Zhejiang Province, China, we collected data on malaria from the Chinese Notifiable Disease Reporting System (NDRS) and analyzed them. A total of 2,738 malaria cases were identified in Zhejiang Province from 2005 to 2014, of which 2,018 were male and 720 were female. Notably, only 7% of malaria cases were indigenous and the other cases were all imported. The number of malaria cases increased from 2005 to 2007, peaked in 2007, and then decreased from 2007 to 2011. There were no indigenous cases from 2012 to 2014. Of all cases, 68% of cases contracted Plasmodium vivax, 27% of cases contracted P. falciparum, and two cases contracted P. malariae. About 88% of malaria cases during 2005-2011 occurred yearly between May and October, but the number of malaria cases in different months during 2012-2014 was similar. The median age was 33 years, and 1,892 cases occurred in persons aged 20-50 years. The proportion of businessmen increased and the proportion of migrant laborers decreased in recent years. The median time from illness onset to confirmation of malaria cases was 5 days and it decreased from 2005 to 2014. Some epidemiological characteristics of malaria have changed, and businessmen are the emphases to surveillance in every month.
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INTRODUCTION
Despite widespread elimination and control efforts during
the 20th century, malaria continues to be the most important
parasitic disease known to humankind. According to the
World Health Organization (WHO) estimate in 2014, there
were 3.2 billion people at risk of being infected with malaria
and developing disease; 198 million cases of malaria and
584,000 deaths occurred globally in 2013.1 Over the span of
the last century, almost half of the world’s countries have
successfully eliminated malaria.2 Although great success has
been achieved since the launch of national malaria control
program in 1955, malaria remains a serious public health
problem in China.3–5 The Chinese Notifiable Disease Report
ing System (NDRS), which was initiated in the 1950s, is the
fundamental communicable disease surveillance system in
China. After the outbreak of severe acute respiratory
syndrome (SARS) in 2003, the Chinese government strengthened
the construction of public health information system. On
January 1, 2004, the Real-Time Notifiable Infectious Disease
Reporting System was put into use nationwide, realizing the
timely online monitoring of individual cases, which marks a
leap in the surveillance of communicable diseases in China.
Zhejiang Province is located in southeastern China,
adjacent to Anhui Province, where malaria is endemic. Malaria
incidence decreased in recent years in Zhejiang Province, but
there were hundreds of imported malaria cases every year
and epidemiological characteristics changed.6,7 This stimulated
us to analyze the updated epidemiological characteristics of
malaria cases in recent years.
Case definition. Indigenous malaria was defined as any
case infected within the province where it was diagnosed; in
contrast, imported malaria was defined as a malaria case whose
origin could be traced to an area of transmission outside the
province where the diagnosis of malaria was made.8,9
Data collection. Daily disease surveillance data on malaria
from 2005 to 2014 were obtained from the NDRS. Information
of cases included gender, age, occupation, residential address,
type of disease, date of onset, and date of confirmation.
Data analysis. Data were analyzed using the Statistical
Package for the Social Sciences (SPSS v19; SPSS, Chicago, IL).
Categorical variables were summarized by frequencies and
numerical variables were summarized by means with standard
deviations if normally distributed and medians, interquartile
ranges (IQRs), and ranges if not normally distributed.
Ethical approval. Experimental research reported in this
study has been performed with the approval of the ethics
committee of Zhejiang Provincial Center for Disease Control
and Prevention (Zhejiang CDC). Human research was
carried out in compliance with the Helsinki Declaration. All
participants provide their written informed consent to
participate in this study.
A total of 2,738 malaria cases were identified in Zhejiang
Province from 2005 to 2014, of which 2,018 were male and
720 were female. Of note, only 7% (183/2,738) of malaria
cases were indigenous and the other cases were all imported.
As shown in Figure 1, the number of malaria cases increased
from 2005 to 2007 and peaked in 2007, and then the number
of malaria cases decreased from 2007 to 2011. Although the
number of malaria cases increased from 2012 to 2014, there
were no (...truncated)