Recent influenza activity in tropical Puerto Rico has become synchronized with mainland US

Abstract

Background We used data from the Sentinel Enhanced Dengue Surveillance System (SEDSS) to describe influenza trends in southern Puerto Rico during 2012‐2018 and compare them to trends in the United States. Methods Patients with fever onset ≤ 7 days presenting were enrolled. Nasal/oropharyngeal swabs were tested for influenza A and B viruses by PCR. Virologic data were obtained from the US World Health Organization (WHO) Collaborating Laboratories System and the National Respiratory and Enteric Virus Surveillance System (NREVSS). We compared influenza A and B infections identified from SEDSS and WHO/NREVSS laboratories reported by US Department of Health and Human Services (HHS) region using time series decomposition methods, and analysed coherence of climate and influenza trends by region. Results Among 23,124 participants, 9% were positive for influenza A and 5% for influenza B. Influenza A and B viruses were identified year‐round, with no clear seasonal patterns from 2012 to 2015 and peaks in December‐January in 2016‐2017 and 2017‐2018 seasons. Influenza seasons in HHS regions were relatively synchronized in recent years with the seasons in Puerto Rico. We observed high coherence between absolute humidity and influenza A and B virus in HHS regions. In Puerto Rico, coherence was much lower in the early years but increased to similar levels to HHS regions by 2017‐2018. Conclusions Influenza seasons in Puerto Rico have recently become synchronized with seasons in US HHS regions. Current US recommendations are for everyone 6 months and older to receive influenza vaccination by the end of October seem appropriate for Puerto Rico.

Viral etiology and seasonal trends of pediatric acute febrile illness in southern Puerto Rico; a seven-year review

“…A recent study comparing the seasonality of influenza viruses in all ages in Puerto Rico to the seasonality in United States Health and Human Services regions, using data from SEDSS, found that in recent years synchronization for both IAV and IBV in both places has increased and suggested that factors like travel and United States influenza viral introductions to Puerto Rico can play an important role in such synchronization [ 42 ]. After the restrictions in travel, local mobility, and social gatherings related to the coronavirus disease 2019 (COVID-19), changes in respiratory viruses’ trends have started to be noticed [ 43 ].…”

Reduced spread of influenza and other respiratory viral infections during the COVID-19 pandemic in southern Puerto Rico

“…As the transmission dynamics of influenza and other respiratory viruses in Puerto Rico are synchronized with mainland US [ 13 ], drops in connectivity due to the disruption of air traffic, decreases in family visits, tourism and cancellation of large gatherings as part of suggested COVID-19 guidelines may have further affected the circulation of these respiratory viral pathogens. While there were no travel border restrictions in Puerto Rico outside of those related to limits on travel to the US from other countries [ 29 ], reductions of cruise ships [ 30 ] and international travel to Puerto Rico may have contributed to a reduction of imported respiratory infections into the island.…”

“…The Sentinel Enhanced Dengue Surveillance System (SEDSS) has been previously described [ 13 , 14 ]. Briefly, we collected data from the Sentinel Enhanced Dengue Surveillance System (SEDSS) in the southern region of Puerto Rico, a surveillance system that has been monitoring acute febrile illness (AFI) trends among three sentinel hospitals in Ponce, Puerto Rico and surrounding municipalities since May 2012 [ 13 , 14 ], and tested for the presence of arboviral and respiratory virus etiologies. Individuals seeking medical care at the three participating hospitals are screened for AFI, defined as reporting fever (>37.5°C) at the time of visit or self-reported fever in the past seven days.…”

“…Enrolled participants complete a questionnaire and nasal swab samples and a serological sample are collected. Nasal swab samples are tested by real time reverse transcriptase polymerase chain reaction (RT-PCR) for several arboviral and respiratory viruses including Influenza (A & B), RSV, AdV, and other respiratory viruses (i.e., human parainfluenza virus types 1 & 3 and human metapneumovirus), as previously described [ 13 , 15 – 17 ].…”

“…There is limited information on the impact of NPIs implemented during the COVID-19 pandemic on respiratory infections in the Caribbean [ 11 , 12 ]. Despite the higher temperatures and humid climate in Puerto Rico, pre-COVID-19 pandemic influenza trends on the island were similar to those in the continental United States, with peak activity occurring in the months of December and January, but often circulating for longer periods than typically observed in the continental US [ 13 ]. A study of pediatric respiratory infections found RSV exhibited similar trends in seasonality to influenza, and AdV having stronger seasonal peaks in the spring and early summer months [ 14 ].…”