Six penguins have died after an outbreak of malaria at London Zoo this summer.
The birds contracted the avian strain of the disease from mosquitoes and died in August, despite the zoo taking extra precautions to prevent the killer infection.
Zookeepers increased the birds' anti-malaria medication due to fears that the wet weather created the perfect conditions for mosquitoes to thrive.
Avian malaria cannot be passed on to humans, nor can it be passed from bird to bird, and the zoo says the remaining penguins are "healthy and well".
A spokeswoman for London Zoo said avian malaria is "endemic" in the UK's wild bird population, highlighting that preventative measures, including anti-malaria medicine, are in place on a daily basis to prevent this "very sad occasion" from happening.
"They have it all the time as a daily dose, given it with their breakfast. We put a tablet in their fish and every single penguin gets one in the morning," she said.
She added: "The keepers also spray lavender oil in the penguins' nest boxes which is a natural deterrent.
"We plant lavender around the enclosure and the penguins use that to build their nests. We do a lot to stop this from happening so obviously it's a very sad occasion."
The spokeswoman said despite efforts to prevent the disease, the "wet, muggy weather" this summer - the wettest in England and Wales for 100 years - created the "perfect conditions for mosquito numbers", therefore increasing the risk of contracting the disease.
Speaking of the remaining penguins, the spokeswoman said: "All the penguins appear healthy and well. Obviously our keepers are keeping a close eye on them, working with the vets, and just making sure we watch them carefully."
London Zoo has three different species of penguin and it was six Humboldt penguins which died, although the spokeswoman said no particular species is more at risk than another.