Coxsackievirus B3, Shandong Province, China, 1990–2010

To determine the cause of a 2008 outbreak of aseptic meningitis in Shandong Province, China, we analyzed samples from outbreak patients and coxsackievirus B3 samples collected during 1990–2010 surveillance. The cause of the outbreak was coxsackievirus B3, genogroup D. Frequent travel might increase importation of other coxsackievirus B3 genogroups.

To determine the cause of a 2008 outbreak of aseptic meningitis in Shandong Province, China, we analyzed samples from outbreak patients and coxsackievirus B3 samples collected during 1990-2010 surveillance. The cause of the outbreak was coxsackievirus B3, genogroup D. Frequent travel might increase importation of other coxsackievirus B3 genogroups.

C oxsackievirus B3 (CVB3) (family Picornaviridae,
genus Enterovirus) is a major human pathogen (1)(2)(3), and CVB3-associated aseptic meningitis is an emerging concern (4). In the summer of 2008, an aseptic meningitis outbreak occurred in southern Shandong Province, People's Republic of China. Shandong is a coastal province with a population of 94.7 million. The huge number of hospitalized children caught the attention of public health offi cials and media and triggered an extensive study on the causative agent. To help determine the cause of the outbreak, we analyzed samples from outbreak case-patients and conducted a molecular epidemiology study of CVB3 isolates collected in Shandong during 1990-2010.

The Study
The 2008 outbreak occurred during June-September and peaked in early July. A total of 887 patients, 596 male and 291 female, were hospitalized. Patient ages ranged from 2 months to 64 years; most (98%) were <15 years of age. Epidemiologic investigation showed that 617 (69.6%) case-patients had a history of contact with aseptic meningitis case-patients, and 159 (17.9%) had drunk untreated well water. The most common clinical manifestations were fever (89.6%), vomiting (57.2%), headache (48.3%), lethargy (14.5%), and rash (1.5%). No sequelae or deaths were reported.
We also analyzed details of clinical and environmental CVB3 strains collected in Shandong since 1990 (Table) by using data from the acute fl accid paralysis (AFP) surveillance system. Because China has no specialized enterovirus surveillance system, no comprehensive molecular epidemiologic data are available for CVB3 or other nonpolio enteroviruses that cause aseptic meningitis. However, the AFP surveillance system, developed for the polio eradication program and conducted in Shandong since 1990, can provide baseline data of local nonpolio enterovirus circulation (8).
According to the AFP surveillance system, during 1990-2010, a total of 768 nonpolio enteroviruses were isolated, and 59 (7.7%) strains were typed as CVB3 by use of a molecular method (6). Frequency of CVB3 isolation fl uctuated from year to year and peaked during 1996, [2000][2001][2002]2005, and 2008 ( Figure 1). The low level of CVB3 before 1996 might be a surveillance artifact because AFP surveillance in China increased substantially throughout the 1990s. CVB3 accounted for ≈21% of all nonpolio enterovirus isolates from AFP case-patients in 2008. Another outbreak of aseptic meningitis outbreak occurred in 2005, during which 57 CVB5 strains were recovered (9) and 2 CVB3 strains were identifi ed. From environmental surveillance, CVB3 was isolated in 2008 (n = 7), 2009 (n = 1), and 2010 (n = 1). In addition, CVB3 was isolated from patients with hand-foot-and-mouth disease (n = 2) and sporadic aseptic meningitis and encephalitis syndrome (n = 4).

Conclusions
Our results indicate that CVB3 was the cause of the outbreak and that most CVB3 isolates were closely related. The AFP surveillance in Shandong, although insuffi cient for monitoring enterovirus infections of humans, revealed a similar fl uctuating epidemic mode for CVB3 with a temporal peak in 1-3 years and quiescence for 2-3 years. The temporal dynamics of echovirus 30, causing nationwide epidemics of 2-4 years separated by periods of quiescence, have been reported (11). The CVB3 peak detected by AFP and environmental surveillance in 2008 correlated well with the aseptic meningitis outbreak, demonstrating high CVB3 activity at that time. Of note, aseptic meningitis surveillance in Hong Kong detected increased CVB3 activity during 2001, 2005, and 2008 (4), consistent with the temporal peak of CVB3 in Shandong. The close genetic relationship between the strains from mainland China and the Hong Kong strains in 2008 suggests that the same strain was circulating in both regions.
Most global CVB3 strains belong to genogroups B and D. During 1970-2006, genogroup B came from the United States, Australia and Europe. However, this genogroup has not yet been found in mainland China. Although genogroup D was composed entirely of strains from China, our data are insuffi cient for us to propose that genogroup D is confi ned to China only. Nevertheless, our study demonstrates that genogroup D has been predominantly circulating in mainland China for the past 20 years and is responsible for all documented outbreaks and sporadic cases of CVB3-associated aseptic meningitis. Because of the more frequent population exchange between China and the rest of the world, the chance for importation of other CVB3 genogroups to mainland China is greatly increased.