Epidemiology of influenza in Ghana, 2011 to 2019

Abstract

Influenza virus is an important contributor to acute respiratory illnesses and is estimated to cause up to 650,000 respiratory deaths each year. Ghana recorded influenza viruses as far back as 1918 when the Spanish influenza pandemic led to the death of >100,000 people in a population of 4 million at the time. An outbreak of highly pathogenic avian influenza A(H5N1) among poultry in Ghana in 2007, led to the establishment of virological surveillance for influenza-like illness (ILI) by the Noguchi Memorial Institute for Medical Research (NMIMR). This surveillance system, supported by the U.S. Naval Medical Research Unit-No. 3 (NAMRU-3) and the Ghana Health Service (GHS), monitors circulating influenza strains and activity to better understand the epidemiology of influenza in Ghana. We present here the results of this surveillance system from 2011 to 2019. As part of the Integrated Disease Surveillance and Response (IDSR) system of the GHS under the Ministry of Health (MOH), oropharyngeal and nasopharyngeal swabs were collected from patients who met a modified World Health Organization (WHO) case definition for ILI or severe acute respiratory illness (SARI) through a sentinel surveillance system in the country. Samples were transported to the National Influenza Centre (NIC) at the NMIMR and tested for influenza virus using protocols defined by the United States Centers for Disease Control and Prevention (CDC). Selected isolates were sent to the WHO collaborating centre in the United Kingdom for further antigenic characterization. From 2011 to 2019, the NIC tested a total of 21,747 ILI samples and 3,429 SARI samples. Influenza positivity rates were highest in the 5–14 year old group for both ILI (20.8%) and SARI (23.8%). Compared to females, more males were seen at the health facilities for ILI and SARI symptoms with a statistically significant difference in influenza positive ILI (15% vs 13.2%, p <0.001). In terms of absolute numbers, more cases were seen at the health centres during the wet seasons (April to October) compared to the dry seasons (November to March) in Ghana. This study presents 9 years of surveillance data from outpatient and inpatient setting on influenza activity as well as the influenza A subtypes and B lineages that drive the activity. This presents useful information for influenza vaccine selection and administration. Ghana’s unique influenza activity patterns also present a challenge in predicting when an outbreak could occur.

Decreased influenza activity during the COVID-19 pandemic in Ghana, 2020

“…In Ghana, influenza circulates all year-round with expected multiple peaks during the major (epi-weeks 14–26) and minor (epi-weeks 32–43) raining seasons ( 13 ). Our observation for 2020 was close to the expected characteristic seasonality in Ghana during the minor raining season.…”

“…Influenza A (H3) and B Victoria dominated in the 2020 surveillance season. The influenza season in Ghana is driven by varying strains of seasonal influenza viruses ( 13 ). The transition between influenza strains and other respiratory pathogens remains unpredictable ( 16 ).…”

Human Seasonal Influenza Viruses in Swine Workers in Lagos, Nigeria: Consequences for Animal and Public Health

“…Interestingly, Ayim-Akonor et al observed a difference in the prevalence of viral RNA-positive swine swabs according to the season, with detection rates 2.5 times higher during the rainy season compared to the dry season in Ghana [ 20 ]. The rainy season also corresponds to the period of increased influenza virus transmission in the Ghanaian population [ 27 ]. Similar observations were made in Kenya, where increased seroprevalence in pigs followed periods of transmission in human population during colder months [ 28 ].…”

Risk Factors for Influenza Disease in Shai-Osudoku and Ningo-Prampram Districts in the Greater Accra Region of Ghana

“…For the period of 2011 to 2019, the National Influenza Center (NIC) received and processed a total of 21,747 respiratory samples from Influenza-Like Illness patients, out of which 3,051 (14.0%) were positive for influenza. Children aged 5-14 years who are the school-going age, documented the highest age-specific influenza positivity rate (21%, 702/3376) [10]. Ntiri et al (2016) in a study at SO and NP Districts in Ghana reviewed the records of 2,322 ILI patients tested from 2014 to 2016.…”