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Vinod Scaria, Afra Shamnath
Monkeypox has recently caught attention, with cases reported from across the world. The present outbreak has a toll of over 220 confirmed cases spread across 19 countries as of date, with the UK, Spain and Portugal leading the pack in the number of confirmed cases and no deaths reported until date. Even though sporadic outbreaks have been reported in and around Africa and a few related to travel in regions endemic to the virus, the present outbreak has been interesting in many ways. Firstly, outbreaks spanning multiple countries simultaneously have not happened before. Secondly, many of the affected patients did not have travel to regions where the disease is considered prevalent and finally, initial cases were largely, but not exclusively among young individuals who identify themselves as men who have sex with men (MSM).
Monkeypox is not a new virus. The virus, belonging to the poxvirus family of viruses, was first identified in monkeys way back in 1958, and therefore the name. The first human case was described in 1970 from the Democratic Republic of Congo and many sporadic outbreaks of animal to human as well as human to human transmission have occurred in central and West Africa in the past with significant mortality. After the elimination of smallpox, Monkeypox has become one of the dominant poxviruses in humans, with cases increasing over years along with progressively younger people getting affected. These outbreaks have been often self-limiting, as close contact is required for disease transmission.Further, the incubation period ranges from 5 to 21 days and majority of affected people are asymptomatic or have mild disease and these cases transmit the disease unknowingly. Since in the majority of affected people, and is often mild or self-limiting, asymptomatic cases could transmit the disease unknowingly. Close contact with animals in areas adjacent to the forest is speculated to have contributed to the outbreak in Central Africa. While monkeys are possibly only incidental hosts, the reservoir is not known. It is believed that rodents and nonhuman primates could be potential reservoirs.
The Genome and mutations
Monkeypox virus is a DNA virus with a quite large genome of around 200,000 nucleotide bases. While being a DNA virus, the rate of mutations in poxviruses is significantly lower (~1-2 mutations per year) compared to RNA viruses like SARS-CoV-2. The low rate of mutation therefore limits the widespread application of genomic surveillance in providing detailed clues to the networks of transmission for monkeypox, unlike what was possible for SARS-CoV-2.
A number of genome sequences in recent years from Africa and across the world suggest that there are two distinct clades of the virus - the Congo Basin / Central African clade and and the West African clade. Further, each of the clades have many lineages. The Central African / Congo basin clade is thought to have a higher transmission and virulence compared to the West African clade.
It is remarkable and noteworthy that the enormous capacity and expertise in sequencing and analysis of genome sequences of viral pathogens built during the COVID19 pandemic has come in handy for investigating the present outbreaks.
With over a dozen genome sequences of monkeypox now available from across the world from the current outbreak, it is reassuring that the sequences are quite identical to each other suggesting a few introductions resulted in the present cases spread across the world. This also roughly corroborates with the epidemiological understanding that the major congregations in the recent past contributed to the widespread transmission across different countries. Unlike COVID-19, the slow rate of mutations preclude us from using genomic sequences for fine-tracing of the contact networks. The virus genomes also show very close similarity (around 45 mutations) with those from the recent outbreak in Nigeria during the 2017-2019 period suggesting that the present outbreak is possibly not driven by a new variant, but potentially related to unique transmission networks.
The genome sequences available at present from the present outbreak belong to the West African lineage of the virus, which has been suggested to be associated with lower virulence. As more genomes become available from across the countries affected, it is possible to potentially uncover the intricacies of transmission networks and evolution of the virus.
Unlike SARS-CoV-2 in 2019, It is reassuring that we know quite a lot more about the virus and its transmission patterns and have effective ways and enormous knowledge base on preventing the spread, apart from an effective vaccine in-hand. The Smallpox/Vaccinia vaccine provides cross-protection against Monkeypox. While the vaccine has been discontinued in 1980 following the eradication of Smallpox, emergency stockpiles of the vaccines are maintained by many countries. Younger individuals are unlikely to have received the vaccine and therefore potentially susceptible to Monkeypox which could partly explain the emergence in younger individuals in the previous as well as present outbreaks.
Learning from the enormous wealth of knowledge from the countries in Africa which have effectively managed the monkeypox outbreaks in the past would go a great way in containing the present outbreak and also help us be prepared for future outbreaks. While we have many effective ways of containing the outbreak, including contact-tracing and an effective vaccine, efforts to bridge the divide - both in health, knowledge, experience and infrastructure could contribute to long-lasting impact in preventing and managing future outbreaks and contribute to an equitable and global public health.
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The authors are researchers at the CSIR Institute of Genomics and Integrative Biology (CSIR-IGIB). All opinions expressed are personal.
A number of genome sequences in recent years from Africa and across the world suggest that there are two distinct clades of the virus - the Congo Basin / Central African clade and and the West African clade. Further, each of the clades have many lineages. The Central African / Congo basin clade is thought to have a higher transmission and virulence compared to the West African clade.
It is remarkable and noteworthy that the enormous capacity and expertise in sequencing and analysis of genome sequences of viral pathogens built during the COVID19 pandemic has come in handy for investigating the present outbreaks.
What do the genomes say ?
With over a dozen genome sequences of monkeypox now available from across the world from the current outbreak, it is reassuring that the sequences are quite identical to each other suggesting a few introductions resulted in the present cases spread across the world. This also roughly corroborates with the epidemiological understanding that the major congregations in the recent past contributed to the widespread transmission across different countries. Unlike COVID-19, the slow rate of mutations preclude us from using genomic sequences for fine-tracing of the contact networks. The virus genomes also show very close similarity (around 45 mutations) with those from the recent outbreak in Nigeria during the 2017-2019 period suggesting that the present outbreak is possibly not driven by a new variant, but potentially related to unique transmission networks.
The genome sequences available at present from the present outbreak belong to the West African lineage of the virus, which has been suggested to be associated with lower virulence. As more genomes become available from across the countries affected, it is possible to potentially uncover the intricacies of transmission networks and evolution of the virus.
Effective vaccine
Unlike SARS-CoV-2 in 2019, It is reassuring that we know quite a lot more about the virus and its transmission patterns and have effective ways and enormous knowledge base on preventing the spread, apart from an effective vaccine in-hand. The Smallpox/Vaccinia vaccine provides cross-protection against Monkeypox. While the vaccine has been discontinued in 1980 following the eradication of Smallpox, emergency stockpiles of the vaccines are maintained by many countries. Younger individuals are unlikely to have received the vaccine and therefore potentially susceptible to Monkeypox which could partly explain the emergence in younger individuals in the previous as well as present outbreaks.
Learning from the enormous wealth of knowledge from the countries in Africa which have effectively managed the monkeypox outbreaks in the past would go a great way in containing the present outbreak and also help us be prepared for future outbreaks. While we have many effective ways of containing the outbreak, including contact-tracing and an effective vaccine, efforts to bridge the divide - both in health, knowledge, experience and infrastructure could contribute to long-lasting impact in preventing and managing future outbreaks and contribute to an equitable and global public health.
----
The authors are researchers at the CSIR Institute of Genomics and Integrative Biology (CSIR-IGIB). All opinions expressed are personal.
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