Saw-scaled vipers are difficult to spot as they tend to be active at night, have venom that drives people to suffer catastrophic internal haemorrhages and live in places where medical care is limited. As such, it is not surprising that they kill an awful lot of people. Antivenoms are widespread and available where these snakes are found but a team of researchers studying survival data noticed that people were still often dying even if they got the antivenom in time. Concerned and confused, the researchers ran an analysis of antivenom performance against venom milked from a number of the vipers and discovered that many of the antivenoms on the market simply do not work in regions where advertising says they should.
The key issue at hand here is the fact that antivenoms are produced using venom and venom varies from snake to snake, sometimes even within the same species. So, if an antivenom is produced using a species of saw-scaled viper found in both India and Pakistan but only snakes from Pakistan have their venom collected for the creation of the drug, there is chance that the antivenom will not work very well (or at all) when used to treat snake bites in India. This is precisely what appears to have happened and the harm to people in Asia and Africa looks like it is quite significant.
Some of the antivenom companies that I spoke with were remarkably receptive to these findings. One clearly stated that they are going to re-label their bottles immediately so their drugs are only delivered to places where they do actually work. Another stated that they are going to start milking vipers from more regions to build better antivenoms. However, not all is rosy. One company flatly denied that they manufacture a very poorly performing antivenom that is advertised on their own website and another argued that the findings of the researchers were flawed. You can read more in The Economist article that I wrote on this here.