The number of varicella cases reported in December 2021 increased from the previous month and was below the previous 5-year average. Due to robust vaccination programs, there is no longer discernable seasonality for varicella cases in the United States.

In December 2021, 51 varicella cases were reported in 21 counties, outlined in black in the map below. From October 2021 through December 2021 the average county rates varied throughout the state.

In 2021, 381 varicella cases were reported in 38 counties. The annual number of reported varicella cases decreased from 2016 to 2017. In 2020 and 2021, case counts are mostly lower than those seen in previous years at this time.

In December, the varicella rate was highest among infants <1 year old at 3.4 cases per 100,000 population, which is consistent with previous months. infants <1 year old are too young to receive varicella vaccination, which is why vaccination of siblings, parents, grandparents and other age groups is important in infection prevention among infants.

In December, 5 cases were transmitted within households and no cases were outbreak-associated. For most varicella cases, exposure to other known cases is not identified. In Florida, transmission setting is not routinely identified for non-outbreak cases, resulting in 64% of cases reporting unknown setting in December.

People with shingles infection can transmit the virus that causes varicella to people without immunity. In December, 2 cases reported having contact with someone diagnosed with shingles during their exposure period