Paramyxoviridae family is a large family of viruses that infect both humans and animals. Viruses in this family are generally called paramyxoviruses. The paramyxoviruses include the most important causative agents of mumps, respiratory infections in young children and infants (i.e., respiratory synctial virus and parainfluenza viruses) as well as the causative agent of measles. Measles is a highly infectious viral disease of global health importance that have been eradicated, even though some outbreak of measles was recorded in some parts of Europe due to some defaults in their immunization/vaccination program against measles infection. However, measles infection has been adequately contained and eradicated in the human population; and thus regular immunization/vaccination is necessary to achieve herd immunity in order to continuously prevent a resurgence of the disease.
Respiratory synctial virus (RSV) is also a member of the paramyxoviruses that causes pneumonia and bronchiolitis in children and infants. Paramyxoviruses have a negative-sense single-stranded RNA [ss(-)RNA] genome. They are enveloped viruses. Structurally, paramyxoviruses have a helical nucleocapsid and they measure between 150-350 nm in diameter. Paramyxoviruses replicate in the cytoplasm of their host cell and they are released by a budding process through the cytoplasmic membrane of the infected host cell. The Paramyxoviridae family is divided into two subfamilies viz: Paramyxovirinae and Pneumovirinae. Paramyxovirinae subfamily is comprised of five genera: Respirovirus (which contain the human parainfluenza viruses – types 1 and 3); Rubulavirus (which contain mumps virus and the human parainfluenza viruses – types 2 and 4); Avulavirus (which contain Newcastle disease and avian parainfluenza viruses); Morbillivirus (which contain measles virus) and Henipavirus (which contain Hendra and Nipah viruses).The Pneumovirinae subfamily contains only two genera: Pneumovirus(which contain the human respiratory synctial virus) and Metapneumovirus (which contain viruses that infect birds such as turkey).
Paramyxoviruses have a worldwide distribution with the exception of viruses in the genera Henipavirus – which are geographically limited and are found in parts of Asia including Malaysia, Singapore and Australia. Majority of the diseases caused by paramyxoviruses including mumps, parainfluenza and measles are known as notifiable diseases; and thus they must be reported to public health authorities for proper action to be taken to contain their outbreak and spread in the human population. Paramyxoviruses are mainly spread through aerosols and the respiratory tract as droplet infections; and they majorly affect children and infants inclusive of adults.
Attenuated live vaccines exist for the prevention of mumps and measles in children and other susceptible human population. Antiviral agents are also available for the treatment of infections caused by paramyxoviruses. Due to the high morbidity and mortality associated with paramyxoviruses infection especially measles (a childhood disease characterized by the appearance of maculopapular rash all over the body), infections caused by paramyxoviruses still remain amongst the preventable diseases that newborns and susceptible populations are vaccinated or immunized against all over the world.
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