A large whooping cough (pertussis) outbreak has been ongoing in people California in 2010. This bacterial infection, caused by Bordetella pertussis, is a highly transmissible disease that can result in serious problems (including death) in young infants. At last report, there were over 6000 cases of whooping cough, making this the largest outbreak in 60 years. Over 200 infants have been hospitalized, and there have been at least 10 deaths. Nine of the 10 deaths were in infants less than two months of age. Infants in this age group have little to no immunity to the disease because they haven't been vaccinated, and they are more prone to severe complications.
Bordetella pertussis is a human bacterium. It does not infect animals and animals are not direct sources of infection. (Actually, experimental infection of neonatal puppies with large doses of B. pertussis can result in shedding of the bacterium by a small percentage of dogs, but that's not particularly relevant to the normal household situation). Therefore, people don't need to worry about infecting their pets and pets passing the infection on to other people. However, it's not impossible that pets could play an indirect role in transmission. A pet's haircoat could possibly become contaminated with the pertussis bacterium from someone coughing around it, or touching it with contaminated hands. The bacterium could survive on the haircoat for a while (probably days), and someone could potentially get the bacterium on their hands by petting it, and subsequently become infected.
What are the odds of this happening? Who knows. It's not something that anyone has investigated, as far as I know.
Could dogs and cats be important sources of pertussis in households? Probably not. I assume that if there is a person with whooping cough in a household, that person is more likely to be the source of infection for other people than a pet.
Could pets spread pertussis outside the home? That might be a more realistic concern. People with pertussis might keep themselves away from others and stay at home, but if they contaminate their dog's coat and the dog meets people on a walk or at the park (or at a veterinary clinic, or anywhere else), I have to wonder whether there could be the potential for spread of the disease.
What should we do about this? Common sense should prevail, and itt's important for pertussis as well as other diseases. If someone in the household has an infectious disease that is transmissible and for which a pet could potentially be a vector, some basic precautions should be taken. Good attention to hygiene might help reduce contamination of the pet's haircoat. This includes regular handwashing (especially after coughing and before petting an animal), avoiding coughing close to the pet and not letting the pet sleep close to the person's head. Keeping the pet away from people outside the house, or at least limiting it's contact with high-risk people might also be useful. In particular, keeping pets that might have been contaminated away from infants would be wise.
Overall, the risks are very low. We don't need to fear dogs and cats as potential pertussis vectors. However, in the absence of proof that there's no risk, and with a highly transmissible and potentially serious disease, use of some simple infection control measures makes sense.