An outbreak of Pontiac fever due toLegionella longbeachaeserogroup 2 found in potting mix in a horticultural nursery in New Zealand

Abstract

SUMMARYPrevious outbreaks of Pontiac fever have invariably been associated with water droplet spread ofLegionellaspp. In January 2007 three workers from a horticultural nursery were admitted to hospital with non-pneumonic legionellosis. Investigations showed that a working party of ten people had been exposed to aerosolized potting mix; nine of these workers met the case definition for Pontiac fever. The presence of genetically indistinguishableLegionella longbeachaeserogroup 2 was demonstrated in clinical specimens from two hospitalized workers and in the potting mix to which they had been exposed. A further seven cases were diagnosed by serological tests. This is the first documented outbreak of Pontiac fever fromL. longbeachaeserogroup 2 confirmed from inhalation of potting mix. Pontiac fever is likely to be under-diagnosed. We advocate the introduction of an industry standard that ensures the use of face masks when handling potting mix and attaching masks and warning labels to potting mix bags sold to the public.