Surveillance systems are major mechanisms to  protect the public against disease.

Statistics can be used to quantify the degree of uncertainty.

The leading cause of death in the US is tuberculosis.

Odds ratios

Most public health data comes from existing data bases.

Epidemiologic studies always involve experiments conducted on human subjects.

The HMO is both an insurer and a provider.

It is difficult to get a reliable number of injuries in the US because many are not reported unless they are fatal.

The greenhouse gas effect is the result of increasing levels of isocyanate in the air.

Which of these are effective in preventing transmission?