Hanta Virus Infecting Humans and Animals in China

Hanta Virus Infecting Humans and Animals in China –  Hemorrhagic fever with renal syndrome (HFRS) may be a serious public ill health within the People’s Republic of China.

China – Although 7 sero genotypes of hantaviruses are found in rodents, only the Hantaan virus (carried by Apodemus agrarius mice) and therefore the Seoul virus (carried by brown rat rats) reportedly cause disease in humans. From 1950–2007, a complete of 1,557,622 cases of HFRS in humans and 46,427 deaths (3%) were reported in China.

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Hantavirus – HFRS has been reported in 29 of 31 provinces in China. After the implementation of comprehensive preventive measures, including vaccination, within the past decade in China, the incidence of HFRS has dramatically decreased; only 11,248 HFRS cases were reported in 2007.
Mortality rates also declined from the very best level of 14.2% in 1969 to ≈1% during 1995–2007. However, the numbers of HFRS cases and deaths in China remain the very best within the world.

Infections in Humans

For humans, individual HFRS cases also as outbreaks are influenced by natural (e.g., ecologic) and occupational factors (3,18,19). Many hantavirus infections occur in persons of low socioeconomic status due to poor housing conditions (6). In China also , occurrence and epidemics of HFRS are influenced by natural and social factors (10,14,20–22). HFRS cases occur mainly within the northeastern, eastern, central, and southwestern parts of China (humid and semihumid zones) and infrequently within the northwestern part (arid zone) (Figure 2). Rural areas account for >70% of HFRS cases; i.e., mainly peasants are infected (9,10). Poor housing conditions and high rodent density in residential areas seem to be liable for most HFRS epidemics.

The increase of HFRS from the top of the 1970s coincided with the fast socio-economic development that started in 1978 in China. During the 1980s and 1990s, China underwent large changes like agricultural development, irrigation engineering, urban construction, mining, and highway and railway construction. These activities might increase human contact with rodents. Because rats are more mobile than other hantavirus hosts (4), fast socio-economic development also causes wide dispersion of rats and SEOV (23), which could subsequently cause the high nationwide prevalence of SEOV infections. However, improved housing conditions, improved hygiene, and human migration from rural areas to cities might contribute to the declining trend of HFRS cases since 2000.

Infections in Animals

Species diversity of rodents and insectivores in China is remarkable (27). a complete of 171 species of rodents, which belong to 10 subfamilies, are found; the subfamilies Murinae and Microtinae contain 38 and 43 species, respectively. additionally , a minimum of 32 species of insectivores is present. These rodent and insectivore species are distributed nationwide. In particularly, A. agrarius and R. norvegicus rodents, the reservoir hosts of HTNV and SEOV, are the predominant species (Table 1) and are found in 28 and 30 provinces, respectively, in China.

Hantavirus Isolates
Antigenic and genetic studies of hantaviruses isolated from HFRS patients and rodents in China found 3 hantaviruses in China: HTNV, SEOV, and Da Bie Shan virus carried by Chinese white-bellied rats (Niviventer Confucius) (Table 2, Figure 3) (11–13). Recently, we found Puumala virus-like Hokkaido virus in Myodes rufocanus voles (29), Khabarovsk virus in Microtus maximowiczii voles, Vladivostok virus in Microtus fortis, subspecies pellicles voles (30), and a presumably novel Yuanjiang virus in M. fortis, subspecies calamorum voles (8). So far, only HTNV and SEOV are known to cause HFRS in China (8–11). Because A. agrarius and R. norvegicus rodents are the predominant carriers and are distributed nationwide, HTNV and SEOV are obviously the main threat for HFRS in China.

Control and Prevention
To control and stop HFRS in China, a comprehensive preventive strategy has been implemented and includes public health education and promotion, rodent control, surveillance, and vaccination (10). Surveillance of hantavirus infection in rodents could help with the organization of a complicated warning service for possible increases in human infections. In 1984, national closed-circuit television was established in China (12). Each province to which HFRS is endemic has a minimum of 1 surveillance laboratory; the amount depends on the severity of HFRS. consistent with an invitation from the Chinese Center for Disease Control and Prevention (previously Chinese Academy of Preventive Medicine), studies are conducted to work out 1) the amount of HFRS cases, 2) the list of local small animal species (including their density in nature and in residential areas), and 3) hantavirus prevalence in rodent and human populations. The system has provided systemic epidemiologic knowledge of hantavirus infection in China.

Inactivated hantavirus vaccine was developed after HTNV and SEOV were successfully isolated and propagated in A-549 cells (31,37,38). Inactivated hantavirus vaccine was first approved in 1993 and, since 1995, has been utilized in areas where HFRS is very endemic. Four hantavirus vaccines supported inactivated HTNV and SEOV are widely used and demonstrated to be safe and efficacious (Table 3) (39). per annum , ≈2 million vaccine doses are used. Purified bivalent vaccine for HTNV and SEOV cultured in Vero cells have been used since 2003 (40). From 2008, the hantavirus vaccine has been included within the national Expanded Program on Immunization. For persons in areas during which HFRS is very endemic, the vaccination is freed from charge.

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