I think the concern comes from the fact that this is a new viral strain, so with seasonal flu it's been studied extensively and therefore scientists know: the R0 (how many people a carrier will go on to further infect); the likely pathways for mutation; how it's transmitted; incubation periods and so on.
So far for this Coronavirus, the R0 appears to be higher than for seasonal flu; they seem to have not yet identified the index case (aka patient zero); a vaccine is still in its early stages of production and testing; it's unclear if the Coronavirus will mutate and if it does, how it will mutate.
Additionally, most seasonal flu cases are transmitted through the respiratory system (someone sneezing or talking and then another person breathing in the infected droplets, or getting them in their eyes and nose, or touching a surface with an infected droplet and then touching eyes, nose, mouth), and humid environments help to decrease the amount of time the virus spends being airborne and I think also reduces the distance infected droplets can travel. However, scientists in China have identified the virus being present in stool samples, so there's the possibility of faecal - oral transmission if sewage waters aren't adequately treated, then the climate conditions don't matter as much as sanitation does.
Also, this is happening during the regular flu season, so if health systems are stretched because of regular illnesses, the last thing they need is an additional burden. So, there's no reason to panic in the UK, but it is something to keep an eye on. And don't be one of those people who go into work even when they're ill...