It explains the influenza epidemiological studies in Nigeria

1. OUTLINE
1
• Introduction of influenza virus
• History of influenza virus in Nigeria
• Aetiology of influenza virus
• Classifications of influenza virus
• Epidemiology of influenza virus in Nigeria
• Immunological response of influenza virus
• Mode of transmission of influenza virus
• Pathogenesis of influenza virus
• Sign and symptoms of influenza virus
• Diagnostic method of influenza virus
• Treatment of influenza virus
• Prevention and control
• Conclusion
• References

2. 2
INTRODUCTION OF INFLUENZA VIRUS
• Influenza virus (commonly called “flu” virus) is a respiratory infection that affect the
upper and lower respiratory system (CDC, 2020).
• It causes diarrhea and vomiting marked by fever, chills, a general body fatigue and
pain in the muscles together with varying degree of soreness in the head and
abdomen (CDC, 2020).
• In 2016 alone, over 2.5 million death was recorded. with influenza virus being the
major contributor (Reiner, 2018).
• The influenza attack rate is mostly in children, while complications including
hospitalization and death occur mostly in elderly individuals (WHO, 2014; Jennings
et al., 2018).
• Influenza viruses can be divided into 4 types; A, B, C, and D (Tong et al., 2012; Tong
et al., 2013).

3. 3
Figure 1: Schematic of Influenza A, B, and C virus structure
(Francis et al., 2019).

4. 4
HISTORY OF INFLUENZA VIRUS IN NIGERIA
Year Historical event References
14th of
September 1918
Influenza pandemic was introduced into Nigeria by passengers and
crews who arrived via ship from overseas.
(Ohadike, 1991)
1936 Thomas Francis Jr. isolated influenza B virus (Francis, 1940)
1936 Macfarlane Burnet discovered that influenza virus could be grown in
embryonated hens’ eggs.
(CDC, 2021)
late 1930s and
1940s
the virus’s characteristics and the development and use of inactivated
vaccines
(CDC, 2021)
1950s The protective efficacy of these inactivated vaccines was demonstrated (CDC, 2021)
1970 First detection of human H3N2 influenza virus in Taiwanese pigs, it
known to occur in other parts of the world, such as in humans, to swine
in Nigeria and Ghana, respectively,
(Adeola et al.,
2016)
1993 Wilson Smith, Christopher Andrewes, and Patrick Laidlaw isolated
influenza A virus in ferrets.
(CDC, 2021)
2003 The first live, attenuated influenza vaccine was licensed (CDC, 2021)
2006 Avian influenza was first reported in Nigeria (Okoli et al.,
2017)
2007 Nigeria confirms its first human case of Avian influenza, in a 22-year-
old woman from Lagos
(WHO,2012)
2008 Nigeria reports H5N1 in poultry in Anambra (WHO, 2012)
2009 Pandemic influenza A virus subtype H1N1 (A[H1N1]pdm09) replaced
A(H3N2) as the dominant circulating virus during November 2009.
(Dalhatu et al.,
2012)
2013 A non-live, recombinant influenza virus vaccine not requiring isolation
or growth in hen’s eggs was licensed
(CDC, 2021)
Table 1: historical event of Influenza in Nigeria

5. 5
AETIOLOGY OF INFLUENZA VIRUS
• Influenza is a disease of the lungs and upper airways caused by
infection with a flu virus (influenza virus)
• And affects the upper and lower respiratory tract (Fathima, et al., 2012;
Tong et al., 2012; Tong et al., 2013).
• Influenza A and B viruses has 8 negative-sense RNA segments make up
the viral genome
• Influenza C and D virus genome has 7 segments (Koutsakos et al.,
2016).
• The eight segments are three polymerase proteins (PA, PB1 and PB2),
the nucleoprotein (NP), the nonstructural protein (NS1), the nuclear
export protein (NEP or sometimes called BNS2), the matrix protein
(BM1), the BM2 ion channel and three surface glycoprotein (HA, NA
and NB) (Koutsakos et al., 2016).

6. 6
Figure 2: Diagram of the structure of influenza virus
(Jalilian et al., 2013).

7. 7
CLASSIFICATIONS OF INFLUENZA VIRUS
GENUS SPECIES GENOMIC SEGMENTS
Alphainfluenzavirus Influenza A virus 8
Betainfluenzavirus Influenza B virus 8
Gammainfluenzavirus Influenza C virus 7
Deltainfluenzavirus Influenza D virus 7
Isavirus Salmon isavirus 8
Quaranjavirus Johnston Atoll quaranjavirus
Quaranfil quaranjavirus
6
Thogotovirus Dhori thogotovirus
Thogoto thogotovirus
6
(Kuchipudi and Nissly, 2018).
Table 2: Classification of family orthomyxoviridea

8. 8
CLASSIFICATIONS OF INFLUENZA VIRUS
• Influenza viruses (IVs) are enveloped, single-stranded RNA viruses with
segmented genomes containing 7–8 gene segments (Kalonda et al., 2021).
• Influenza A viruses are divided into subtypes based on two proteins on the surface
of the virus: hemagglutinin (H) and neuraminidase (N).
• There are 18 different hemagglutinin subtypes and 11 different neuraminidase
subtypes.
• It undergoes antigenic drift and antigenic shift, and causes a pandemic (CDC,
2019).
• Influenza B viruses are divided into 2 lineages: Yamagata and Victoria.
• It undergoes antigenic drift and causes causes annual epidemics due to limited host
range compare to IAV (Budd et al., 2017).
• Influenza type C viruses are not associated with severe disease, epidemics, or
pandemics,
• Influenza D viruses primarily affect cattle and not humans (Tong et al., 2012; Tong
et al., 2013).

9. 9
Figure 3: Summary of the wide host range of influenza viruses (Asha and Kumar, 2019).

10. 10
Figure 4: Diagram of the global epidemiology of influenza virus (WHO, 2020).

11. 11
EPIDEMIOLOGY OF INFLUENZA VIRUS IN NIGERIA
• Epidemiology is a branch of medical science that deals with the incidence,
distribution, and control of disease in a population.
• Each year over 250,000 African children aged less than 5 years are hospitalized
with influenza and have influenza-associated hospitalization rates more than 3
times higher than those of children in industrialized countries (Lafond et al.,
2016).
• Since 2006, in West Africa including Nigeria, have established influenza
surveillance (Talla Nzussouo et al., 2017).
• The seasonality of influenza viruses in the tropics has been associated with the
rainy season.
• In Nigeria, however, many studies of respiratory diseases, including those
caused by influenza viruses, have suggested a closer correlation with the dry
harmattan season (WHO, 2019).

12. 12
EPIDEMIOLOGY OF INFLUENZA VIRUS IN NIGERIA
S/N STUDY TITLE STUDY
METHOD
STATE POPUL
ATION
PREVELA
NCE
SPECI
MEN
SAMPLE
TYPE
REFERENCE
1 Seasonal influenza
among
unvaccinated
pregnant women
EIA LAGOS 182 56.6% Human Blood (Anjorin and
Nwammadu,
2020)
2 Prevelence of
influenza A in
piggy workers
PCR Lagos 197 87% human Blood (Awosanya et al.,
2013)
3 Serological
evidence of
seasonal influenza
virus in Nigeria
PCR Lagos 174 84.1% human Blood (Anjorin and
Adeopoju, 2020)
4 Influenza virus A
(H1 and H3) and B
co-circulation
among patient
presenting with
acute respiratory
tract infection in
Ibadan, Nigeria.
Haemagglu
tination
and
haemagglu
tination-
inhibition
assays
Ibadan 128 16.4% Humans Throat swab (Odun-ayo et al.,
2018)
Figure 3: Epidemiology of influenza virus in Human

13. 13
EPIDEMIOLOGY OF INFLUENZA VIRUS IN NIGERIA
S/
N
STUDY
TITLE
STUDY
METH
OD
STATE POPUL
ATION
PREVELA
NCE
SPECIM
EN
SAMPLE
TYPE
REFERENCE
1 Surveillance of
influenza A
RT-PCR OYO 239 1.9%(93/15
6)
DOGS Blood (Dauda and
Adebowale, 2018)
2 Detection of
pandemic
strains of
influenza virus
ELISA IBADA
N
125 8% PIGS Nasal
swab
(Oluwagbenga et
al., 2015)
4 Serology of
equine
influenza virus
ELISA Kano ,
Kaduna,
Katsina,
Lagos,
Porthaco
urt
80 19% horses Serum (Adeyefa et al.,
1996)
5 Equine
influenza virus
serology
ELISA kaduna 375 16% horses Serum (Meseko et al.,
2020)
6 Detection of
influenza A
virus in pigs
RT-PCR Lagos 116 26.7% Pigs Nasal and
throat
swab
(Anjorin et al.,
2011)
Figure 4: Epidemiology of influenza virus in Animals

14. 14
EPIDEMIOLOGY OF INFLUENZA VIRUS IN NIGERIA
S/N STUDY TITLE STUDY
METHO
D
STATE POPULA
TION
PREVEL
ANCE
SPECIME
N
SAMPLE TYPE REFERENCE
7 Serologic and
virologic
surveillance of
avian influenza in
Nigeria
PCR Farms in all
states in
Nigeria
13,597 24.8% Bird 1205-routine
diagnostic samples
8638-clocal swab
7,976-tracheal swab
7328-sera
616-
Carcassses
(Joannis et al.,
2008)
8 Complete genome
sequencing of
H1N1pdm09
swine influenza
isolates from
Nigeria
RT-PCR Lagos state
and
southwest
Nigeria
299 13.7% Pigs Nasal swab (Meseko et al.,
2020)
9 Reverse zoonotic
transmission of
influenza virus in
Lagos state,
Nigeria.
RT-PCR Lagos 1972-pigs
432
humans
(pig
handlers)
1.3%-Pigs
0.005%-
humans(p
ig
handlers)
Pigs and
humans
Nasal and
oropharyngeal swabs
(Anjorin et al.,
2020)
Figure 4: Epidemiology of influenza virus in Animals

15. 15
Figure 5: Map of Nigeria showing the surveillance points and Highly Pathogenic Avian Influenza
H5N1 status during the targeted HPAI surveillance in Nigeria, 2006-2008 (Laleye et al., 2012).

16. 16
Figure 6: The innate and adaptive immunity against influenza virus (Bao et al., 2013).

17. 17
Figure 7: Mode of transmission of Influenza (Tellier et al., 2019).

18. 18
Figure 8: Pathogenesis of influenza virus (Yamaya and Shimotai, 2016).

19. 19
Figure 9: Phases of influenza virus pathogenesis.
(Gounder and Boon, 2019).

20. 20
Figure 10: Symptoms and complications of Influenza (Ghebrehewet et al., 2016).

21. 21
DIAGNOSTIC METHOD OF INFLUENZA VIRUS
Method Types
Detecte
d
Acceptable Specimens Test
Time
Reference
s
Antigen detection ELISA A and B Nasopharyngeal (NP) swab, throat swab, nasal
wash, bronchial wash, nasal aspirate, sputum
2 hours Samra et
al., 2010
Rapid Influenza Diagnostic Tests
(antigen detection)
A and B Nasopharyngeal (NP) swab, aspirate or wash,
nasal swab, aspirate or wash, throat swab
< 15min. CDC, 2020
Rapid Molecular Assay [influenza viral
RNA or nucleic acid detection]
A and B NP swab, nasal swab 15 – 30
minutes
CDC, 2020
Immunofluorescence, Direct (DFA) or
Indirect (IFA) Florescent Antibody
Staining [antigen detection]
A and B NP swab or wash, bronchial wash, nasal or
endotracheal aspirate
1 - 4
hours
CDC, 2020
RT-PCR (singleplex and multiplex; real-
time and other RNA-based) and other
molecular assays [influenza viral RNA
or nucleic acid detection]
A and B NP swab, throat swab, NP or bronchial wash
,nasal or endo tracheal aspirate, sputum
Varies (1
to
8hours,
varies by
the
assay)
Samra et
al., 2010
Rapid cell culture (shell vials; cell
mixtures; yields live virus)
A and B NP swab, throat swab, NP or bronchial wash,
nasal or endotracheal aspirate, sputum;
(specimens placed in Viral transport media
(VTM))
1 - 3
days
CDC, 2020
Viral tissue cell culture (conventional;
yields live virus)
A and B NP swab, throat swab, NP or bronchial wash,
nasal or endotracheal aspirate, sputum
(specimens placed in VTM)
3 – 10
days
CDC, 2020
Table 5: Methods for Detecting Influenza virus

22. 22
TREATMENT OF INFLUENZA VIRUS
Drug name Route Activity
against
Use Recommended for Not recommended for Adverse events
Oseltamivir Oral Influenza
A and B
Treatment Any age Not applicable Nausea, vomiting, headache.
Chemo-
prophylaxi
s
3 months and older Not applicable Post marketing report of serious
skin reactions And sporadic,
transient neuropsychiatric
events.
Zanamivir Oral
inhalation
Influenza
A and B
Treatment 7 years and older People with underlying
respiratory disease (e.g.,
asthma, COPD (Chronic
obstructive pulmonary
disease)
Risk of bronchospasm,
especially in the setting of
underlying airways disease;
sinusitis, and dizziness.
Chemo-
prophylaxi
s
5 years and older People with underlying
respiratory disease (e.g.,
asthma, COPD (Chronic
obstructive pulmonary
disease)
Post marketing report of serious
skin reactions And sporadic,
transient neuropsychiatric
events.
Paramivir Intraveno
us
Influenza
A and B
Treatment 2 years and older Not applicable Diarrhea
Chemo-
prophylaxi
s
Not recommended Not applicable Post marketing report of serious
skin reactions And sporadic,
transient neuropsychiatric
Boloxavir Oral Influenza
A and B
Treatment 12 years and older Not applicable None
Chemo-
prophylaxi
s
Approved for post-
exposure prophylaxis in
persons 12 years and
older
More common than placebo in
clinical trials
Table 6: Summary of antiviral agent for influenza
(CDC, 2021).

23. 23
Figure 11: Preventions of influenza (CDC, 2020).
NOTE: The two available forms of vaccines are intramuscular trivalent inactivated vaccine (TIV)
and intranasal live attenuated influenza vaccine (LAIV).

24. 24
CONCLUSION
The majority of the deaths and severe illness occur in low- and middle-income
countries especially in Africa such as Nigeria with a large population, where there
is little or scanty information on epidemiological surveillance. Therefore more
epidemiological studies and surveillance is necessary.

25. 25
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