2064 EmergingInfectiousDiseases•www.cdc.gov/eid•Vol.27,No.8,August2021
RESEARCH
B
y the end of October 2020, the severe acute respi-
ratory syndrome coronavirus 2 (SARS-CoV-2)
pandemic had spread to 6 continents and caused
>45 million coronavirus disease (COVID-19) cases
and 1.1 million deaths (1). Despite having 15.6% of
the worldwide population (2), by October 31, 2020,
Africa had only 3.9% (1.76 million) of the world’s
COVID-19 cases and 3.6% (42,233) of deaths during
the pandemic (1). Data suggest that the pandemic
is evolving differently in sub-Saharan Africa com-
pared with the rest of the world and that the out-
break started later (3).
Of note, severe COVID-19 cases seem to occur
less frequently in Africa than in the rest of the world
(4). Several factors have been proposed to explain
this. Age is likely a major factor because older per-
sons are at higher risk for severe disease, but Africa
has an extremely young population; >60% of persons
are <25 years of age (5). However, variation of CO-
VID-19 severity with age alone does not fully explain
the observed differences (4). Clinical cases and deaths
in Africa likely are underreported because systematic
surveillance is limited and no systematic death regis-
tration exists; thus, the true SARS-CoV-2 burden prob-
ably is underestimated (4). Nevertheless, local health
systems in Africa, which have a lower capacity to deal
with COVID-19 patients than healthcare systems in
high-resource settings, were not overwhelmed, even
at the peak of the epidemic (6). Although potential
Intense and Mild First
Epidemic Wave of Coronavirus
Disease, The Gambia
BaderinwaAbatan,OrighomisanAgboghoroma,FataiAkemoke,MartinAntonio,BabatundeAwokola,
MustaphaBittaye,AbdoulieBojang,KalifaBojang,HelenBrotherton,CarlaCerami,EdClarke,
UmbertoD’Alessandro,ThushandeSilva,MariamaDrammeh,KarenForrest,NatalieHofmann,
SherifoJagne,HawanatuJah,SheikhJarju,AssanJaye,ModouJobe,BeateKampmann,
BubaManjang,MelisaMartinez-Alvarez,NuredinMohammed,BehzadNadjm,
MamadouOusmaneNdiath,EsinNkereuwem,DavisNwakanma,FrancisOko,EmmanuelOkoh,
UduakOkomo,YekiniOlatunji,EniyouOriero,AndrewM.Prentice,CharlesRoberts,AnnaRoca,
BabandingSabally,SanaSambou,AhmadouSamateh,OusmanSecka,AbdulKarimSesay,
YankubaSinghateh,BubacarrSusso,EuaUsuf,AminataVilane,OghenebrumeWariri
1,2
Authoraliations:MedicalResearchCouncilUnitTheGambiaat
theLondonSchoolofHygieneandTropicalMedicine,London,
UK(B.Abatan,O.Agboghoroma,F.Akemoke,M.Antonio,
B.Awokola,A.Bojang,K.Bojang,H.Brotherton,C.Cerami,
E.Clarke,U.D’Alessandro,T.deSilva,K.Forrest,N.Hofmann,
H.Jah,S.Jarju,A.Jaye,M.Jobe,B.Kampmann,M.Martinez-
Alvarez,N.Mohammed,B.Nadjm,M.O.Ndiath,E.Nkereuwem,
D.Nwakanma,F.Oko,E.Okoh,U.Okomo,Y.Olatunji,E.Oriero,
A.M.Prentice,A.Roca,O.Secka,A.K.Sesay,B.Susso,E.Usuf,
A.Vilane,O.Wariri);MinistryofHealth,Banjul,TheGambia
(M.Bittaye,M.Drammeh,S.Jagne,B.Manjang,C.Roberts,
B.Sabally,A.Samateh,S.Sambou,Y.Singhateh)
DOI:https://doi.org/10.3201/eid2708.204954
1
Authorsarelistedinalphabeticalorder.
2
AllauthorswerepartoftheMRC/GambianGovernment
COVID-19WorkingGroupandcontributedequallytothisarticle.
The severe acute respiratory syndrome coronavirus 2
(SARS-CoV-2) pandemic is evolving dierently in Africa
thaninotherregions.AfricahaslowerSARS-CoV-2trans-
missionrates andmilder clinicalmanifestations. Detailed
SARS-CoV-2epidemiologicdataareneededinAfrica.We
usedpubliclyavailable data to calculateSARS-CoV-2in-
fectionsper1,000personsinTheGambia.Weevaluated
transmissionrates among1,366 employees ofthe Medi-
cal Research Council Unit The Gambia (MRCG), where
systematicsurveillanceofsymptomaticcasesandcontact
tracing wereimplemented. By September 30,2020, The
Gambiahad identied3,579 SARS-CoV-2 cases,includ-
ing 115 deaths; 67%of cases were identied inAugust.
Amonginfections,MRCGstaaccountedfor191cases;all
wereasymptomaticormild.Thecumulativeincidencerate
among nonclinical MRCG sta was 124 infections/1,000
persons,whichis>80-foldhigherthanestimatesofdiag-
nosed cases among the population. Systematic surveil-
lanceandseroepidemiologicsurveysareneededtoclarify
theextentofSARS-CoV-2transmissioninAfrica.
EmergingInfectiousDiseases•www.cdc.gov/eid•Vol.27,No.8,August2021 2065
avoidance of medical care during the pandemic, as
described in other regions (7), could partly explain
the low number of hospitalized patients, the milder
COVID-19 disease severity reported appears to be
genuine, and several biologic and environmental fac-
tors have been proposed as potential contributing
factors (8–10).
Recent serosurveys conducted in Kenya, Malawi,
and South Africa showed that community transmis-
sion was several times higher than that detected by
surveillance; 5%–40% of the population had SARS-
CoV-2 IgG (11–13). Such results highlight the need for
robust epidemiologic studies to assess the extent of
community transmission in different regions in Africa.
The Gambia is the smallest country in continen-
tal mainland Africa and is surrounded by Senegal,
except for its narrow Atlantic coast. Although an im-
ported case was identied in The Gambia on March
17, 2020, by June 30, 2020, only 48 additional cases had
been detected. Nevertheless, a rapid increase in cases
was seen in July 2020, and by the end of September
2020, 3,579 cases were reported (1). The trajectory of
the epidemic in The Gambia is different from that in
Senegal, which has a population ≈7 times larger than
The Gambia. In Senegal, community transmission
was reported in early April 2020, and almost 7,000
cases were recorded by the end of June (1). Systemat-
ic surveillance, testing, contact tracing for staff of the
Medical Research Council Unit The Gambia (MRCG)
at the London School of Hygiene and Tropical Medi-
cine (https://www.mrc.gm) who had inuenza-like
symptoms was implemented during the pandemic;
the rst case among MCRG staff was identied on
July 18. We considered MRCG staff as a cohort to
provide additional insights into the nature of the CO-
VID-19 epidemic in The Gambia.
Methods
Population Demographics, Climate, and
Healthcare Structure
In 2020, The Gambia had a population of ≈2.42 mil-
lion. The median age is 17.8 years, and ≈41.9% of
the population are 20–64 years of age. About 95% of
the population is Muslim. The illiteracy rate is high
across the country. Around 59% of the population
live in urban and peri-urban settings, mainly along
the coast (Figure 1).
The climate is typical of the sub-Sahel region,
including a long dry season during November–May
and a short rainy season during June–October. Maxi-
mum temperature is high throughout the year, 30°C–
34°C, and lowest during the rainy season; minimum
temperatures range from 22°C–24°C during the rainy
season to 16°C−20°C during the dry season (14). Hu-
midity can be >80% during the rainy months (15).
The government of The Gambia is the main
health provider, and healthcare delivery has 3 tiers,
based on the primary healthcare strategy in which
most healthcare delivery occurs at local health posts.
The Gambia has 4 tertiary hospitals, 38 health centers
at the secondary level, and 492 health posts at the pri-
mary level. The system is complemented by 34 pri-
vate and nongovernmental organization clinics.
COVID-19 Response in The Gambia
Shortly after the rst COVID-19 case was detected in
The Gambia on March 19, 2020, the country closed its
international land, sea, and air borders. On March 27,
the country declared a state of emergency, which in-
cluded closing schools, nonessential shops, places of
worship, and many workplaces. Initial SARS-CoV-2
testing by PCR was focused on identifying imported
cases and tracing and isolating case contacts, espe-
cially among travelers from Senegal. The Ministry of
Health, supported by several international organiza-
tions, set up a hotline for the public, which persons,
including those with suspected cases, could call to
ask for advice or request the surveillance team to per-
form the SARS-CoV-2 test either at health facilities or
at home.
As the epidemic progressed, the Ministry of Health
established testing facilities at strategic locations in the
most densely populated parts of the country, mainly
the western urban areas. Persons were encouraged to
go for testing if they were symptomatic or after contact
with a conrmed COVID-19 case. Demand for testing
services was not high, and attempts to raise awareness
were unsuccessful. All identied cases were isolated
in designated facilities regardless of symptoms until
considered noninfectious as per World Health Organi-
zation (WHO) guidelines (16). Ministry of Health staff
traced and quarantined contacts for 10 days in hotels
during the early part of the outbreak, April–July 2020,
after which persons were permitted to self-isolate for
10 days at home.
MRCG Unit
MRCG is a biomedical research institution that
also provides outpatient and inpatient clinical care
to the local population through its clinical servic-
es department (CSD). As of August 2020, MRCG
had 1,336 employees. Staff were distributed as fol-
lows: 845 were along the coast, mainly in Fajara;
158 were in Keneba; 116 were in the Central River
Division, mainly in Farafenni; and 217 were in the
MildFirstEpidemicWaveofCOVID-19,TheGambia
RESEARCH
2066 EmergingInfectiousDiseases•www.cdc.gov/eid•Vol.27,No.8,August2021
Upper River Division, mainly Basse (Figure 1).
MRCG staff work in different environments, includ-
ing 715 (53.5%) eld-based staff, such as drivers,
community workers, nurses, and research clinicians;
334 (25.0%) ofce-based staff, including those in ad-
ministrative, operations, data-management, and sta-
tistics positions; and 177 (13.2%) laboratory-based
staff. Only 110 (8.2%) MRCG staff provide health-
care to the general population at the CSD.
CSD is 1 of 2 hospital facilities in The Gambia able
to care for severe COVID-19 patients. CSD dedicat-
ed 42 beds for COVID-19 patients, including MRCG
staff and the general population. From the start of the
epidemic, all staff were trained to wear appropriate
personal protective equipment (PPE) according to in-
ternational guidelines (17).
MRCG staff underwent a clinician-administered
risk assessment in the early phases of the epidemic.
Staff deemed to be at high risk for severe disease were
advised to work from home and were excluded from
high-risk clinical areas.
Surveillance and Contact Tracing among MRCG Sta
In July 2020, MRCG established enhanced passive
case detection by testing all staff exhibiting COV-
ID-19 symptoms, such as cough, fever, headache, sore
throat, nasal congestion, body pain, or other inuen-
za-like symptoms. Families and contacts of symp-
tomatic staff also were tested, as were staff known to
have been exposed to conrmed cases. In addition,
CSD staff were offered active weekly PCR-based test-
ing, regardless of symptoms. MRCG set up a hotline
manned by doctors from whom staff could receive
answers to questions or concerns and get information
on how to access services. Case contacts were called
to conrm exposure and then tested 3–5 days after the
last exposure. Regardless of negative test results, all
exposed staff were quarantined for 14 days; SARS-
CoV-2–positive staff isolated in their homes for 14
days, or at the MRCG site if at-home isolation was not
possible, in line with WHO recommendations (18).
Sample Collection
Samples were collected via nasopharyngeal swab,
oropharyngeal swab, or both by using FLOQSwabs
(COPAN Diagnostics, https://www.copanusa.com).
Samples were placed in single tubes containing uni-
versal transport medium (COPAN Diagnostics) and
delivered to the laboratory within 24 hours. Sampling
methods were comparable across cohorts with simi-
lar operational procedures and training.
Laboratory Methods for SARS-CoV-2 Detection
MRCG laboratories collaborated with national
public health laboratories to support national test-
ing throughout the country during the epidemic.
MRCG and these laboratories used the same labora-
tory methods and assays. Because the outbreak was
expected to spread to the West Africa subregion,
MRCG staff attended an Africa Centres for Disease
Control and Prevention (https://africacdc.org) re-
gional training workshop on diagnosing COVID-19,
which was held in February 2020 in Dakar, Senegal.
Thereafter, The Gambia established laboratory pro-
tocols for processing and testing suspected SARS-
CoV-2–infected samples according to WHO guide-
lines (19,20). The same procedures and assays were
transferred to the laboratory.
The standard test for COVID-19 diagnosis in The
Gambia is real-time reverse transcription PCR (RT-
PCR) of SARS-CoV-2–specic viral gene sequences. In
the early stages of the outbreak, RT-PCR diagnosis was
made by using the Berlin Charité Laboratory protocol
(21), which targets the RNA-dependent RNA poly-
merase and envelope protein gene. Subsequent tests
kits, primarily the Da An Gene Nucleic Acid Extraction
Kit (Da An Gene Co., Ltd., of Sun Yat-sen University,
https://en.daangene.com) and Novel Coronavirus
Figure 1.PopulationdensityofTheGambia,includingMedicalResearchCouncilUnitTheGambia(MRCG)researchsitesdistributed
acrossthecountry.
EmergingInfectiousDiseases•www.cdc.gov/eid•Vol.27,No.8,August2021 2067
MildFirstEpidemicWaveofCOVID-19,TheGambia
(2019-nCoV) Nucleic Acid Diagnostic Kit (Sansure Bio-
tech, Inc., http://eng.sansure.com.cn) were donated to
the national public health libraries; both tests target
the open reading frame 1ab and the nucleocapsid gene
coding regions.
Sample inactivation and downstream RNA ex-
traction were done by using commercially available
kits according to the manufacturers’ protocols. Ini-
tial extractions were performed manually by using
the QIAamp Viral RNA Mini Kit (QIAGEN, https://
www.qiagen.com) or the IndiSpin Pathogen Kit (IN-
DICAL BIOSCIENCE, https://www.indical.com).
When donations to the public health system became
available, kits from the Da An Gene Co., Ltd., of Sun
Yat-sen University and Sansure Biotech, Inc., were
included. As the outbreak progressed and daily
sample numbers increased, automated RNA extrac-
tion system on the QIAcube HT (QIAGEN) was im-
plemented. In all cases, 200 µL of universal transport
medium sample was processed, and the RNA eluted
in 50–80 µL, depending on the extraction kit. RT-
PCR analysis was conducted with 5 µL of extracted
RNA in 25 µL of reaction mix containing reaction
buffer, one-step reverse transcription enzyme, ei-
ther the Takara One Step PrimeScript III RT-PCR Kit
(TaKaRa Bio, Inc., http://www.takara-bio.com) or
SuperScript III Platinum One-Step qRT-PCR Kit (In-
vitrogen, https://www.thermosher.com), and the
primer and probe mix.
Samples were dened as positive if amplication
of any viral gene occurred after 40 cycles and with all
the controls amplifying as appropriate. We dened a
COVID-19 case as any person with a SARS-CoV-2–
positive RT-PCR from a nasopharyngeal or oropha-
ryngeal swab sample, regardless of symptomatology.
Statistical Analysis
We calculated rates of risk for COVID-19 per 1,000
persons among the population of The Gambia. For
MRCG, we stratied rates by occupational clinical
exposure for staff working at the CSD versus non-
CSD staff. In addition to occupational clinical expo-
sure, surveillance for CSD staff was more intense
due to routine testing, regardless of symptoms or
known exposure.
The Ministry of Health generated daily national
data for The Gambia (22). We extracted compiled data
from the publicly available Johns Hopkins University
COVID-19 database (23). The Gambian Government/
MRCG Joint Ethics committee approved the study
(reference no. L2020.E37).
Results
Persons <25 years of age and persons >60 years of
age are underrepresented in the MRCG cohort com-
pared with the population of The Gambia, (Table).
In addition, urban residents are overrepresented
in the MRCG cohort; 67.6% of MRCG staff live
in cities or towns compared with 59.4% of the over-
all population.
SARS-CoV-2 Positivity Rates
From the start of the epidemic through September
30, 2020, a total of 17,885 samples were tested in
The Gambia; 20.1% (3,590) were SARS-CoV-2–posi-
tive. The positivity rate was lower before July (1.6%;
40/3,095 samples tested) and higher during July–Sep-
tember (23.7%; 3,499/14,790 samples tested) (19,20).
The number of samples collected and the positivity
rate were the highest during August–September 2020,
during which time the number of daily swabs collect-
ed varied from 28 to 524/day (median 184/day) (Fig-
ure 2). Positivity rate also varied substantially, from
<5% to >50%. Approximately 67% of conrmed cases
were detected in August; overall, 60% of conrmed
cases were among persons <40 years of age (20).
During July 1–September 30, a total of 937 sam-
ples were collected from the MRCG cohort; 191
Table. EpidemiologicanddemographiccharacteristicsofthepopulationofTheGambiaandstaffofMRCG*
Baselinecharacteristics
TheGambia,no.(%)
MRCGstaff,no.(%)
Age groups, y†
<25
1,549,084(64.2)
51(3.89)
25–34
367,334(15.2)
450(34.35)
35–44
217,500(9.0)
381(29.08)
45–54
132,917(5.5)
307(23.44)
55–64
72,500(3.0)
113(8.63)
>65
74,917(3.1)
8(0.61)
Medianage,y
17.8
37.5
Sex
M
1,193,834(49.4)
915(68.5)
F
1,220,418(50.6)
421(31.5)
Living in main towns or cities‡
1,420,600(59.4)
903(67.6)
*MRCG,MedicalResearchCouncilUnitTheGambiaattheLondonSchoolofHygieneandTropicalMedicine.
†Ages were missing for 6 MRCG staff.
‡For MRCG staff location, we considered the workplaceratherthanthelivingplace.
RESEARCH
2068 EmergingInfectiousDiseases•www.cdc.gov/eid•Vol.27,No.8,August2021
(20.4%) were SARS-CoV-2–positive. Most (60%) con-
rmed cases were detected in August. The median
age among MRCG staff with SARS-CoV-2–positive
samples was 36 years.
Rates of Infection and Death
By the end of September 2020, the cumulative rate
of infection among the population of The Gambia
≈1.5/1,000 persons (Figure 3, panel A). During the
same period, 115 COVID-19 deaths were recorded
across the country.
Among MRCG staff, stratied analysis showed
that infection rates among CSD staff were 2.6 times
higher than among non-CSD staff, whom we consid-
ered representative of the infection risk among the
general population (Figure 3, panel B). By the end of
September, the cumulative risk for infection among
non-CSD MRCG staff was ≈124/1,000 persons (Fig-
ure 3, panel B). All 191 conrmed cases among
MRCG staff were either asymptomatic or mildly
symptomatic; no cases met WHO criteria for moder-
ate or severe pneumonia and no deaths occurred in
this cohort.
Discussion
The COVID-19 pandemic arrived in The Gambia in
July 2020, later than in most countries in the world.
The Gambia had a short and intense rst wave; 67%
of cases occurred in August, and most cases were as-
ymptomatic or mild. Among our MRCG cohort, 1/7
(14.3%) persons were SARS-CoV-2–positive. During
the epidemic peak, the SARS-CoV-2 positivity rate
among the population of The Gambia was >20%.
The later start of the epidemic is probably the re-
sult of the early closure of national borders, including
for air travel, and of the identication and isolation of
infected persons who continued to enter the country
from Senegal. These measures were complemented
by contact tracing and by the provision of facilities
for quarantine by the government. The relative ef-
fects of these measures, together with other measures
implemented during the state of emergency, such as
closure of schools, reduction of access to markets,
banning of large gatherings including at religious fes-
tivals, and use of facemasks, are hard to quantify, as
are behavioral changes, such as social distancing and
handwashing. Nonetheless, these measures seem to
have been key in preparing the country to respond
and minimize potential harm.
The sudden increase of cases in August coincided
with the major Muslim feast of Eid-Ul Adha, locally
called Tobaski, on July 30, 2020, during which travel
and family gatherings were common. However, the
number of COVID-19 cases had already started to in-
crease in July.
Although climate in The Gambia is hot through-
out the year, the peak epidemic coincided with the
months of highest daily humidity and highest mini-
mum temperature but lowest maximum temperature
(14,15). Data on how temperature and humidity affect
transmission are contradictory (24,25). In The Gambia,
climate conditions might have had an indirect effect on
transmission because persons are more likely to spend
time indoors during the rainy season. In The Gambia,
the rainy season also occurs during the months with
the highest respiratory virus transmission (26).
Figure 2.Numberofdaily
nasopharyngealandoropharyngeal
swabsamplestestedforsevere
acuterespiratorysyndrome
coronavirus2andpercentageof
positivesamplesinTheGambia
duringAugust–September2020,
thetimeframeforthemostintense
transmissioninthecountry.