An Updated Guide To COVID-19 Transmission Rates In N.H.


Between the updated CDC masking guidance released in July and the new, more limited eviction moratorium, levels of community transmission of COVID-19 have become more central in federal and local policymaking in New Hampshire.

A map from the Centers for Disease Control and Prevention (CDC) shows Coos County with high rates of community transmission, and all other counties, except for Sullivan, with substantial rates. Sullivan County is the only county in the state with low rates.

Stay In The Know: Sign up for NHPR’s Rundown newsletter.

In areas with substantial or high levels of COVID-19 community transmission, a return to mask-wearing indoors, even for the fully vaccinated, is recommended by the CDC, and evictions in those counties have been paused. State health officials have issued no formal guidance to Granite Staters in substantial or high transmission counties to resume indoor mask-wearing, although towns may choose to implement a local order.

But New Hampshire and the CDC measure community transmission levels slightly differently. Depending on the source, a county may have a different level of transmission. Guidance for masking and the eviction moratorium follows the CDC’s data.

Both the CDC and the State of New Hampshire use two metrics to measure community transmission levels; test positivity rate and new cases. In both maps, if the two indicators suggest different transmission levels, the higher level is selected. Metrics like vaccinations, hospitalizations, or deaths are not included.

Why does the CDC map look different than the state’s map?

  1. The CDC has four levels of community transmission; low, moderate, substantial and high. The state of New Hampshire has three levels; minimal, moderate, and substantial.
  2. The CDC uses the new case rate per 100,000 residents from the last seven days while New Hampshire includes the last fourteen days.
  3. The CDC only includes test results from the most reliable methods of COVID-19 testing like PCR tests. New Hampshire includes the rate from both PCR and antigen tests.

How the CDC is measuring community transmission levels.

N.H. transmission rates indicator

How the state of New Hampshire is measuring community transmission levels.

We’re continuing our coverage of COVID-19 and the vaccination effort in New Hampshire. Questions about this story? Reach out to