Murray Leinster 
This World is Taboo 

The Interstellar Medical Service was just about the only remaining galactic organization that every one of the hundreds of inhabited planets respected. So when their service broke down in Star Sector Twelve, it created a very dangerous situation. When Calhoun took his Med ship out of overdrive near that sector’s planet Weald, he was vaguely aware of the risks. But the crisis came home to him with a crash the moment he radioed in for landing coordinates. 'Contamination! Full mobilization! Red alert! Death to blueskins!’ Such were the nature of his greetings. And it began to look like a case of the cosmic jitters that only the most drastic of orbital surgery could cure.