According to a recent warning by an expert in infectious diseases, unprecedented levels of immunosuppression in countries such as Australia and the US need to be considered in planning for the real risk of smallpox re-emerging in the world.
“Smallpox was eradicated in 1980 but in 2017, Canadian scientists created a smallpox-like virus in a lab using just mail-order DNA,” said Raina MacIntyre, Professor of Infectious Disease Epidemiology at the University of New South Wales, Sydney, Australia. “Now in 2018, these same scientists published a step by step method to create a pox virus in a lab, making the threat of smallpox re-emergence even greater.”
Professor MacIntyre also said that experts have long feared this scenario, and it is now a reality: “This highlights the real risk of smallpox re-emerging in the world, without terrorists needing to access closely guarded stockpiles of the virus.”
Professor MacIntyre led a study that used a mathematical model to identify the impact of smallpox re-emerging in cities like Sydney and New York, US. The research found that the highest rates of smallpox infection in these cities would be in people aged under 20 years, but the highest death rates would be among people aged 45 and over.
The research also explored whether past vaccination in older people provided much protection. It found that, despite widespread past vaccination in New York, the modelled impact of smallpox in this city was more serious than in Sydney due to its larger number of immunosuppressed people.
“Vaccine immunity wanes over time, and recent vaccination is needed for protection. The good news is, people who have been vaccinated in the past would have a faster response to re-vaccination in the event of an outbreak,” said Professor MacIntyre. “The bad news is, both cities show the highest smallpox infection rates for unvaccinated young people, aged five to 20 years.”
The study also highlighted the need for health workers to be vaccinated and for hospitals to have appropriate isolation facilities to minimise the impact of a smallpox outbreak.
“Should there be a smallpox attack with a virus similar to the virus which was eradicated, the prospects for bringing an epidemic under control are good, with good public health follow up and vaccination of contacts,” said one of the study’s authors, Professor Mike Lane, Emeritus Professor from Emory University in the US and the former Director of the US Centers for Disease Control Smallpox Eradication Program.