Any time there is an outbreak of an infectious disease, the public wants to know how common it is and its risk of contracting it. When covering breaking cases, journalists should provide context by including information on historical incidence and trends.
Here are some resources for infectious diseases exclusively within the United States.
The U.S. Centers for Disease Control and Prevention maintain a National Notifiable Diseases Surveillance System (NNDSS) which tracks all nationally notifiable conditions, which are diseases that health departments are required to report when they have a local case. (Tip: Clicking on each disease in this list shows the case definition and how long it has been a notifiable condition.) This spreadsheet shows whether a disease was reported during each of the years included. Diseases are reported for the week, month and year-to-date in each Morbidity and Mortality Weekly Report.
To see how many cases were reported during a particular month or up through the year-to-date, look for the Notifiable Diseases and Mortality Tables link for the month and year you need from 2015 or 2016. The CDC also provides MMWR summaries of cases for nationally notifiable conditions during each past year back to 1993. Be sure to read “What Data Users Should Know” about the National Notifiable Diseases Surveillance System before you dig into the data. Here are definitions of key terms and other helpful information for understanding the system.
You can also look up state-level data on specific notifiable diseases, and other data from the NNDSS, which is part of the CDC’s overall data site. The State Health Statistic page of the MMWRs contains links to the MMWR Notifiable Diseases Data Tables, NNDSS Morbidity Tables, and Mortality Tables by week, year, and any of 122 cities. You may also find helpful information from data sets in the CDC’s Wide-ranging Online Data for Epidemiologic Research, or WONDER.
Influenza is tracked through the extensive and granular Weekly U.S. Influenza Surveillance Report (FluView). For emerging viruses, the CDC will often set up a disease-specific page, as it did for MERS, SARS and Zika. This is where it tracks U.S. cases.
You can query specific data sets for HIV/AIDS, hepatitis, sexually transmitted diseases and tuberculosis at the National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention Atlas. The National Center for Health Statistics has links for tracking new annual tuberculosis, salmonella, Lyme and meningococcal cases as well as trends and data for AIDS/HIV, influenza, measles, pneumonia, sexually transmitted diseases, viral hepatitis and whooping cough/pertussis.
Most vaccine-preventable diseases have pages for trends and historical data, such as these for measles and pertussis. A caution though: it sometimes can be difficult to find precisely the information you need. For example, this table of pertussis cases by year historically is not accessible from the main pertussis page or pertussis surveillance page for some reason.