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Laboratory-Based Surveillance

The following graphs depict the aggregate results of PDPH's respiratory virus surveillance. Care should be taken with the interpretation of these results.

These summaries display the provisional, year-to-date counts (or, in some cases, percentage positivity) of respiratory viruses by week of report. Comparable data for preceding years are shown as well.

All surveillance data are preliminary and are not intended for further distribution.

Week 52

Week 52: For week 52 of 2021, rhinovirus remained the predominant circulating non-influenza respiratory virus, with approximately 11% of tested specimens positive for rhinovirus. Rhinovirus percents are similar to previous seasons this time of year. RSV activity has increased this week and is currently circulating at lower levels to previous seasons before the COVID-19 pandemic. Parainfluenza virus 3 activity has continued to circulate at higher levels than previously seen while parainfluenza virus 2 activity has decreased this week. Parainfluenza virus 1 activity remains low. Adenovirus has activity decreased this week. Human metapneumovirus cases have decreased with week but is still at higher counts compared to previous seasons for this time of year.

Week 51

Week 51: For week 51 of 2021, rhinovirus remained the predominant circulating non-influenza respiratory virus, with approximately 19% of tested specimens positive for rhinovirus. Rhinovirus precents are similar to previous seasons this time of year. RSV activity has decreased this week and is currently circulating at lower levels to previous seasons before the COVID-19 pandemic. Parainfluenza virus 3 activity has continued to circulate at higher levels than previously seen while parainfluenza virus 2 activity has decreased this week. Parainfluenza virus 1 activity remains low. Adenovirus has activity increased this week. Human metapneumovirus cases have decreased with week but is still at higher counts compared to previous seasons for this time of year. Note: Data for 5 of the 6 sentinel laboratories have been reported. Data will be further updated once additional data is received.

Week 48

For week 48 of 2021, rhinovirus remained the predominant circulating non-influenza respiratory virus, with approximately 24% of tested specimens positive for rhinovirus. After a peak in week 45, rhinovirus activity has decreased this week. RSV activity has slightly increased this week and is currently circulating at similar levels to previous seasons before the COVID-19 pandemic. Parainfluenza virus 3 activity has continued to circulate at higher levels than previously seen while parainfluenza virus 2 activity has decreased this week. Parainfluenza virus 1 activity remains low. Adenovirus and human metapneumovirus activity continued to increase this week, with human metapneumovirus cases increasing significantly compared to previous seasons for this time of year.

Week 45

For week 45 of 2021, rhinovirus remained the predominant circulating non-influenza respiratory virus, with approximately 34% of tested specimens positive for rhinovirus. Over the past weeks, rhinovirus activity has increased, and is currently circulating at higher levels than previous seasons. Parainfluenza 2 and parainfluenza 3 virus activity has also continued to circulate at higher levels than previously seen. Recently, human metapneumovirus and adenovirus activity has begun to increase to higher levels of circulation than previous seasons. RSV, which had an unusually significant peak in September, had decreasing activity until the end of October, when activity began to increase again, though this recent increase is consistent with past seasons. Parainfluenza virus 1 activity remains lower than previous seasons.

Week 35

For week 35 of 2021, RSV was the predominant circulating non-influenza respiratory virus, with approximately 19% of tested specimens positive for RSV. Over the past weeks, RSV activity has continued to increase to abnormally high levels compared to recent seasons for this time of year. Additionally, parainfluenza virus 2 activity has increased recently compared to previous years. In contrast, rhinovirus activity has decreased to levels consistent with previous seasons while parainfluenza virus 3 activity has also continued to decrease since its summer peak. Parainfluenza virus 1, human metapneumovirus, and adenovirus are currently circulating at levels consistent with previous seasons.

Week 30

For week 30 of 2021, rhinovirus remained the predominant circulating non-influenza respiratory virus, with approximately 23% of tested specimens positive for rhinovirus. Additionally, RSV activity has continued to increase during July, with approximately 14% of tested specimens positive for RSV. This sustained trend is abnormal given that RSV typically circulates at very low levels during the summer months. Parainfluenza virus 3 activity has also continued to remain high; however, the trend is similar to previous seasons before the COVID-19 pandemic, though it has occurred slightly later in the season than previous years. Parainfluenza virus 2 activity recently increased to higher levels compared to previous years. Adenovirus and human metapneumovirus activity have remained consistent with previous seasons while parainfluenza virus 1 activity has remained lower than previous seasons.

Week 23

For week 23 of 2021, rhinovirus was the predominant circulating non-influenza respiratory virus, with approximately 33% of tested specimens positive for rhinovirus. During May and June, rhinovirus and RSV activity has continued to increase to a higher percent positivity in contrast to previous seasons. The increase in RSV activity is abnormal given that RSV generally circulates at low levels during the summer months. Parainfluenza virus 3 cases have also increased significantly; however, the trend is similar to previous seasons before the COVID-19 pandemic. Adenovirus and parainfluenza virus 2 activity has remained consistent with previous seasons while human metapneumovirus and parainfluenza virus 1 activity has remained lower than previous seasons.

Week 14

For week 14 of 2021, rhinovirus has remained the predominant circulating non-influenza respiratory virus, with approximately 18% of tested specimens positive for rhinovirus. After a sharp increase in activity in March, rhinovirus activity has decreased during April to levels similar to previous seasons. Adenovirus activity has remained consistent with previous seasons. RSV, human metapneumovirus, and parainfluenza virus activity has remained lower than previous seasons.

Week 3

For week 3 of 2021, rhinovirus was the predominant circulating non-influenza respiratory virus, with approximately 15% of tested specimens positive for rhinovirus. Rhinovirus activity has been variable, but has shown an increasing trend in January, occurring earlier in the year than the past two seasons. Adenovirus activity has remained consistent with previous seasons. RSV, human metapneumovirus, and parainfluenza virus activity has remained significantly lower than previous seasons.