Emerging and re-emerging viruses in Malaysia, 1997-2007

Abstract

Over the past decade, a number of unique zoonotic and non-zoonotic viruses have emerged in Malaysia. Several of these viruses have resulted in significant morbidity and mortality to those affected and they have imposed a tremendous public health and economic burden on the state. Amongst the most devastating was the outbreak of Nipah virus encephalitis in 1998, which resulted in 109 deaths. The culling of more than a million pigs, identified as the amplifying host, ultimately brought the outbreak under control. A year prior to this, and subsequently again in 2000 and 2003, large outbreaks of hand-foot-and-mouth disease due to enterovirus 71, with rare cases of fatal neurological complications, were reported in young children. Three other new viruses - Tioman virus (1999), Pulau virus (1999), and Melaka virus (2006) - whose origins have all been linked to bats, have been added to the growing list of novel viruses being discovered in Malaysia. The highly pathogenic H5N1 avian influenza has also been detected in Malaysia with outbreaks in poultry in 2004, 2006, and 2007. Fortunately, no human infections were reported. Finally, the HIV/AIDS epidemic has seen the emergence of an HIV-1 recombinant form (CRF33_01B) in HIV-infected individuals from various risk groups, with evidence of ongoing and rapid expansion.

Figure 1

Zoonotic, non-zoonotic, and vector-borne viruses emerged in Malaysia between 1997 and 2007. The abbreviations for the viruses and their year(s) of emergence at various locations in Malaysia are shown. Viral outbreaks in Singapore during the same period are also indicated. HPAI H5N1, highly pathogenic avian influenza subtype H5N1; NiV, Nipah virus; CHIKV, chikungunya virus; EV-71, enterovirus 71; HIV-1 CRF33_01B, HIV type 1 circulating recombinant form (CRF33_01B); MelV, Melaka virus; TiV, Tioman virus; PulV, Pulau virus; SARS-CoV, severe acute respiratory syndrome coronavirus.

Figure 2

Phylogenetic reconstruction of the deduced amino acid sequence of the complete N gene of select Paramyxovirinae subfamily members. Nipah virus and Tioman virus, two newly emergent paramyxoviruses in Malaysia, are clustered within the Henipavirus and Rubulavirus genus, respectively. Rubulavirus genus: MuV, mumps virus; MenV, Menangle virus; TiV, Tioman virus; MaV, Mapuera virus; SV5, simian parainfluenza virus 5; SV41, simian parainfluenza virus 41; hPIV2, human parainfluenza virus 2; hPIV4a, human parainfluenza virus 4a; hPIV4b, human parainfluenza virus 4b. Respirovirus genus: SeV, Sendai virus; hPIV3, human parainfluenza virus 3. Henipavirus genus: NiV, Nipah virus; HeV, Hendra virus. Morbillivirus genus: MeV, measles virus; CDV, canine distemper virus. Avulavirus genus: NDV, Newcastle disease virus. Unclassified viruses: SalV, Salem virus; TPMV, Tupaia paramyxovirus.

Figure 3

(a) Cumulative numbers of HIV-1 infections, AIDS cases, and AIDS-related deaths reported by the Ministry of Health in Malaysia (1986–2007). Inset: Distribution of HIV-1 infections in different risk categories. Abbreviations: IDU, injecting drug user; Hetero, heterosexual; Homo/Bi, male homo-/bisexual; MCT, mother-to-child transmission. (b) Structural representation of the novel HIV-1 CRF33_01B identified in Malaysia. Full-length genetic sequence revealed short subtype B fragments are recombined into the gag and pol gene in the backbone of CRF01_AE. The recombinant structures of all HIV-1 CRFs are available at the HIV Sequence Database, Los Alamos National Library.