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of poliomyelitis.

      However, in September 2020 it was announced that Africa was finally free of the polio virus (the wild version: there are still vaccine-derived cases, as described above). The last case of the disease on the continent was recorded in Nigeria in 2016. While science provided an effective vaccine that eliminated polio in most countries, clearing the African continent of the virus is actually a triumph of thousands of health and social workers and campaigners who have fought tirelessly over the years to ensure that the vaccination programmes worked, despite all the obstacles. Without their commitment, this would have never been possible.

But polio still exists in the world. It remains in Afghanistan and Pakistan, where the vaccines didn’t reach war-torn zones to which neither the UN nor the WHO had access. In Pakistan, extremist leaders have proclaimed fatwas against vaccinators, claiming that the vaccine isn’t safe. In India, the problems are mainly overcrowding and poor hygiene, which facilitates transmission of the virus. Until these obstacles are overcome, total eradication of polio won’t be feasible.

Cost in lives, cost in money

      It is calculated that infections have a very high economic cost owing to the consequences both of their mortality and the temporary or permanent disability they cause. This is easier to see in certain epidemics or pandemics. For example, the 1994 outbreak of plague in India caused a massive exodus of 0.5 million people, together with the closing of factories and, logically, a reduction of tourism in the country. It’s estimated that the cost of this was $2,000 million. The 1991 cholera epidemic in Peru paralysed not only tourism but also the fishing industry, as all fish exports were stopped. The losses amounted to some $775 million. The 2003 SARS epidemic cost Asia $140,000 million, mainly due to the decline in tourism. We don’t yet know what the cost will be of having paralysed the world economy for some months because of COVID-19, but it too is expected to be thousands of millions of dollars.

      But epidemics don’t have to affect humans in order to have a major social and economic impact. Recall that the United Kingdom lost about $6,000 million as a result of the bovine spongiform encephalopathy (BSE) outbreak in the 1980s and 1990s (aka mad cow disease), which put an end to meat exports for several years.

In cases of endemic diseases, the calculations become complicated. For example, it’s believed that the economic losses because of AIDS in some African countries could amount to as much as a third of their gross domestic product. Tuberculosis causes annual losses of around $12,000 million. A 1995 study showed that countries where malaria is endemic have incomes that are 33 per cent lower than those of countries where the disease is absent, with a GDP loss of 15 per cent.

      All of this demonstrates that infectious diseases have a major impact on diminishing a country’s wealth, so finding a way to eliminate them is an important strategy, not only for saving lives but also for reducing poverty and assisting developing countries.