**3. Discussion**

In Brazil, first cases of DHF occurred after the introduction of DENV-2 in the State of Rio de Janeiro. The cases of DHF by DENV-2 occurred after an epidemic by DENV-1 in Rio de Janeiro four years ago (Dias et al. 1991; Zagne et al., 1994). The same pattern was seen in Cuba during the 1981 epidemic with sequential infection by two serotypes (DENV-1 and DENV-2), and an interval of six months to five years or so (Kouri et al., 1986).The dynamics of epidemic of dengue in the Amazon is similar to that of other regions of Brazil and America. In Manaus – Amazonas, the first cases of dengue were registered in March 1998 by serological studies during the first epidemic of dengue (Figueiredo et al., 2004). In 2001, it was possible to identify the DENV-1 as the causative agent of that epidemic (Figueiredo et al., 2002). That same year, cases of dengue hemorrhagic fever were registered in the State of Amazonas, with the viral isolation of DENV-2 (Figueiredo et al., 2002). In 2002, DENV3 was first isolated from a patient coming from Bahia. Since then, DENV-3 was diagnosed by viral isolation from several patients with DF (Figueiredo et al., 2003).The virus DENV-4 was detected during the first epidemic reported in Brazil in Boa Vista-Roraima in 1981-1982. At

Molecular Characterization of Dengue Virus

associated with DHF in the Asian continent.

**5. Recognition** 

**6. References** 

(2): 122.

hemorrhagic dengue fever in other regions.

DF. Most of them are associated with mild DF.

Circulating in Manaus, the Capital City of the State of Amazonas, Brazil 87

emergence of new serotypes followed by cases of dengue hemorrhagic. The emergence of DENV-4 in 2008 did not just caused a major epidemic with severe and fatal cases. Other serotypes were also observed. It is possible due to competition between with other serotypes, DENV-4 took some time to become established and the population might have been protected by antibodies obtained in heterologous infections by heterologous serotypes. The viral strain should be studied in detail since it is an Asian genotype that has been




Laboratory of Virology at the Foundation for Tropical Medicine Dr. Hector Vieira Gold (FMT/HVD); Dr. RajendranathRamasawmy for review of the manuscript; ConselhoNacional

Araújo et al. Concurrent infection with dengue virus type-2 and DENV-3 in apatient from Ceará, Brazil.*MemInstOswaldo Cruz,* Rio de Janeiro, 2006. 101(8): 925-928. Burke DS, Nisalak A, Johnson De, Scott RM, 1988. A prospective study of dengue infections

Castro, M.G.; Nogueira, R.M.; Schatzmayr, H.G.; Miagostovich, M.P.; Lourenco-De-Oliveira,

Cunha, R.V. & Nogueira, R.M. Dengue E Dengue Hemorrágico. In: *Dinâmica das* 

Dash, P.K. et al. Reemergence of dengue vírus type-3 (subtype-III) in Índia.Implications for

De Melo FL, Romano CM, De Andrade Zanotto PM. Introduction of Dengue virus 4 (DENV-4) genotype I in Brazil from Asia?PLoSNeglTrop Dis. 2009; 3(4):390. Dias, M.; Zagne, S.M.O.; Pacheco, M.; Stavola, M.S.; Costa, A.J.L. Dengue

Figueiredo, R.M.P.; Bastos, M.S.; Lima, M.L.; Almeida, T.C.; Alecrim, W.D. Dinâmica da

R. Dengue vírus detection by using reverse transcriptionpolymerase chain reaction in saliva and progeny of experimentally infected *Aedesalbopictus* from Brazil.

hemorrágicoemNiterói.*Revista da SociedadeBrasileira de Medicina Tropical*, 1991. 24

sorologia e isolamento viral na epidemia de dengue em Manaus (1998-2001). In:

visitors from around the world, other viruses need to be investigated.

de DesenvolvimentoCientífico e Tecnológico (CNPq) for financial support.

in Bangkok.Am J TropMed Hyg, 1988,38:172– 180.

*doençasInfecciosas e Parasitarias,* 2005. p.1767-1781.

increased incidence of DHF & DSS.*Virology Journal*, 2006.

*MemInstOswaldo Cruz*, 2004.99: 809-814.

that time the DENV-1 was also found (Osanai, 1984). Since then, no isolate of DENV-4 was recorded anywhere else in the country until later in the year 2008 DENV-4 was isolated in Manaus from patients with DF (Figueiredo et al., 2008).

The DENV-4 present in the State of Amazonas and analyzed by nucleotide sequence was shown to belong to genotype I, only present in the Asian continent and never described in the Americas (De Melo et al., 2009).

Dengue fever in uncomplicated cases of co-infection has also been observed by other authors, contradicting the hypothesis that simultaneous infection with dengue virus permits the emergence of a more severe disease (Santos et al., 2003; Araújo et al.,2006). In areas where more than one serotype are transmitted at the same time, clinical cases caused by more than one serotype of dengue fever can be common (Lorono et al., 1999). The high rate of cases occurring during epidemics can result in many infections with multiple serotypes in humans (both clinical and subclinical), and also provide opportunity for mosquitoes to become infected with two or more serotypes (Gubler et al., 1985; Burke et al., 1988). This suggests that co-infection by multiple dengue serotypes may influence the clinical expression of disease and it was initially considered as an explanation for the emergence of DHF (Hammon, 1973).The Amazon is situated in the Northern Region of Brazil, bordered to the north with the State of Roraima, Venezuela and Colombia to the east with the State of Pará, the southeast by the State of Mato Grosso, to the south with the State of Rondônia and southwest with the State of Acre and Peru (Viverde Tourism). The proximity to other countries where endemic DENV-4 is observed as in Venezuela and Colombia may have influenced the detection of this serotype first in the Amazon. Besides the geographical location, being today a city with eco-tourism development, and the Industrial Pole of Manaus, with over 450 factories of large, medium and small size (PORTAL AMAZON), which attracts investors from around the world. Manaus receives many people from these and other states and countries.

It is important to remember that the DENV-3 was first detected in Manaus from a patient coming from Salvador-Bahia (Figueiredo et al., 2003).The analysis of the region the C/prM of the DENV-3 in this study belonged to genotype III strains. All DENV-3 isolated in the Amazon were very close to the Indian strain GWL-60 (N°acessoAY770512) and the Brazilian strain BR-74 886 (N access AY679147). Subtype III is related to outbreaks of DHF in India (Dash et al., 2006). In Brazil, the prevalence of DENV-3 two years after its introduction in 2000 was associated with major epidemics in terms of more severe clinical manifestations, and the number of deaths (Nogueira et al., 2005). Twenty-two isolates were classified as DENV-3 subtype III (Miagostovich et al., 2002). The similarity of these strains to other represented by the same genotype III ranged from 96% to 98% and 98-99% for sequences nucleotides and amino acids, respectively. These data demonstrate that this virus is circulating around the world, again indicating high potential for distribution, adaptation in in various geographic areas of the world. This subtype has been implicated in outbreaks of DHF in Asia, Africa and the Americas, and has high potential to cause a pandemic of dengue (Messer et al., 2003).

#### **4. Conclusions**

The emergence of dengue virus in Manaus follows the same pattern as to what occurs in other Brazilian cities. Every two to three years there are new outbreaks of dengue and the emergence of new serotypes followed by cases of dengue hemorrhagic. The emergence of DENV-4 in 2008 did not just caused a major epidemic with severe and fatal cases. Other serotypes were also observed. It is possible due to competition between with other serotypes, DENV-4 took some time to become established and the population might have been protected by antibodies obtained in heterologous infections by heterologous serotypes. The viral strain should be studied in detail since it is an Asian genotype that has been associated with DHF in the Asian continent.

