H7N9. The number of infections with the H7N9 avian influenza virus strain, which has thus far killed more than 20 people, continues to rise in China. Infections have been linked to exposure to poultry, and although there is little evidence for human-to-human transmission, reports of family clusters are a cause for concern. There are suspicions that many mild infections go undetected, which means that identifying the viral reservoirs and monitoring transmission are difficult. WHO/BBC News

Measles. The number of cases of measles in the Welsh city of Swansea has now exceeded 1,000 since November 2012. The epidemic is attributed to the low uptake of the measles, mumps and rubella (MMR) vaccine in the 1990s owing to false claims that it was linked to autism. A catch-up vaccination campaign is ongoing in Wales, and in England one million unvaccinated schoolchildren will now be targeted for preventative measures. BBC News/ Independent