Zoonotic diseases are caused by infectious microorganisms like bacteria or viruses, and are passed between animals, including humans. While some may be mild, others may be life-threatening; they include Ebola, Zika, and salmonellosis, for example. Public health would benefit greatly if we knew about these diseases before they cause major outbreaks, but usually, we’re not aware of a zoonotic disease until people have fallen ill. Researchers are now trying to proactively identify new viral diseases and prevent a potential epidemic by surveying animals for new viruses. In work reported in PLOS Pathogens, researchers at Charité – Universitätsmedizin Berlin focused an investigation like this on insects.
"Every new virus we find could be a cause of illnesses that was previously unknown, both in humans and in livestock," noted Professor Dr. Christian Drosten, Director of the Institute of Virology on Campus Charité Mitte. Drosten is a virus discovery and diagnostics expert at the German Center for Infection Research (DZIF), who previously helped create an internationally recognized diagnostic test for MERS. Now he wants to apply genetic sequencing technologies to the identification of rare, unknown viruses.
"The more viruses we identify and add to our database, the easier it is for us to recognize the cause of new and unusual illnesses," explained Drosten.
Cells carry a genome full of genes, but cells don’t express all of those genes at the same time; gene expression can depend on many factors, including an organism’s age or a cell’s function within an organism, among other things. To study active genes, researchers determine which genes are transcribed by a cell, called the transcriptome.
In this work, the researchers utilized a massive database of insect transcriptomes, and looked for data regarding viral genomes. Viruses with genomes made from negative RNA strands include many known pathogens including rabies, measles and viruses that cause lung infections. Instead of only looking at known disease vectors like mosquitoes, the scientists took all insects in the database into account.
The investigators assessed 1,243 species of insects, and discovered classifiable viruses in twenty new genera or more. "This is probably the largest sample of animals ever screened for new viruses," said Drosten.
They added the viruses they found to databases, so that unusual illnesses might be diagnosed more easily in people that display symptoms of a viral infection with no apparent cause.
"In such cases, we use high-throughput sequencing methods to search for all the viruses present in the patient," added Drosten. "If the patient has a virus, we will find it, provided it is in our database or has similarities with a virus in our database."
Right now in China, researchers are trying to determine the cause of an illness that has sent around 30 people to the hospital with pneumonia (as discussed in the video above). They may be ill with an unknown virus. Research like this will hopefully help reduce the number of cases that can’t be diagnosed.