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ORIGINAL ARTICLE
Year : 2020  |  Volume : 13  |  Issue : 1  |  Page : 22-27  

The observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria


1 Department of Hematology, University of Medical Sciences Teaching Hospital Complex, Ondo City, Ondo State, Nigeria
2 Department of Clinical Pharmacology and Therapeutics, University of Medical Sciences, Ondo City, Ondo State, Nigeria
3 Department of Radiology, Trauma Surgical Centre, University of Medical Sciences, Ondo City, Ondo State, Nigeria
4 Department of Public Health Services, State Ministry of Health, Akure, Nigeria
5 Department of Community Medicine, University of Medical Sciences, Ondo City, Ondo State, Nigeria

Date of Submission02-Jan-2019
Date of Decision20-Aug-2019
Date of Acceptance03-Sep-2019
Date of Web Publication16-Dec-2019

Correspondence Address:
Olumuyiwa John Fasipe
Department of Clinical Pharmacology and Therapeutics, Faculty of Basic Clinical Sciences, University of Medical Sciences, Along Laje Road, Ondo City, Ondo State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mjdrdypu.mjdrdypu_5_19

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  Abstract 


Background: The Lassa viral hemorrhagic fever disease (LVHFD) outbreak usually occurs in the Northern senatorial district of Ondo State, Nigeria. Precisely local government areas (LGAs) such as Ose and Owo LGAs; these are the adjacent LGAs to Edo State in Nigeria where LVHFD outbreak has been recorded highest in the country at recent times. Aim: This research was designed to disseminate a general public awareness message about the recent trend regarding the observed seasonal variation pattern in the epidemiological transmission, outbreak, and status of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria. Materials and Methods: This was a retrospective observational longitudinal study carried out to report the recent trend regarding the observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria. The data in this study were sourced and collected from the state epidemiological records on Lassa fever (LF) at the Department of Public Health Services, Epidemiology Unit, State Ministry of Health, Akure, Ondo State, Nigeria. Results and Findings: The outbreak of the disease has been recurring since 2014 up till date (2018). LF outbreak in the period under consideration showed an increasing trend, except in 2015, where the rate of seropositively infected and confirmed cases reduced by 62.5% (dropped from 8 to 3 cases). The rate of confirmed seropositive cases increased by 533.3% in 2016 compared to 2015, 300% in 2017 compared to 2016, and 19.7% increase in 2018 compared to 2017 events. The mortality rate recorded which was also directly dependent on the rate of confirmed seropositively infected cases; it was 50% in 2014, 0% in 2015, 63.1% in 2016, 23.6% in 2017, and 25.3% in 2018. Furthermore, the peak seropositive outbreak cases for Lassa viral hemorrhagic fever disease in the year 2017 analyses occurred during February (12 cases) and August (12 cases), and then followed by June (11 cases) and December (9 cases). Conclusion: The observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria, can be attributed the challenging poor socioeconomic factors and persistent situations peculiar to the outbreak. The year 2017 analyses revealed that there was an all year round disease outbreak for LF in the state. This was contrary to the widely circulating report that LF outbreak is being influenced by dry seasons. The peak of the disease outbreak in the year 2017 occurred during February and August, as this is the peak months of dry seasons and wet seasons, respectively, in Ondo State, Nigeria.

Keywords: Disease status, epidemiological transmission, Lassa viral hemorrhagic fever disease, observed seasonal variation pattern, outbreak


How to cite this article:
Osho PO, Fasipe OJ, Osho ES, Adu BS, Akinrotimi OJ, Folayan WA, Adebimpe WO. The observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria. Med J DY Patil Vidyapeeth 2020;13:22-7

How to cite this URL:
Osho PO, Fasipe OJ, Osho ES, Adu BS, Akinrotimi OJ, Folayan WA, Adebimpe WO. The observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria. Med J DY Patil Vidyapeeth [serial online] 2020 [cited 2020 Jul 7];13:22-7. Available from: http://www.mjdrdypv.org/text.asp?2020/13/1/22/272882




  Introduction Top


Lassa fever (LF), also known as Lassa hemorrhagic fever or Lassa viral hemorrhagic fever disease (LVHFD), is an acute viral illness that occurs in the West Africa region. It is caused by Lassa mammarenavirus (LASV).[1],[2] The disease was discovered in 1969 when two missionary nurses died at Lassa town, in Borno State, Nigeria. The virus can spread between people through direct contact with the body fluids of a person infected with LF, as well as contaminated bedding and clothing.[3],[4],[5] Nigeria is endemic for LF with an observed 21.3%[6] seropositive prevalence for LF in a countrywide study for Nigeria. It is spread by contact with infected rodent's feces [7] or urine,[8] inhaling contaminated dust,[9] eating contaminated food,[10] or by contact with the fluids of an infected person dead or alive.[11] The multimammate mouse, Mastomys natalensis[7],[8] is the rodent reservoir of the Arenaviridae species,[7],[8] the virus responsible for LF. Furthermore, Ondo State in Nigeria has not been left out in the occurrence of an outbreak of the LF in recent times with outbreak occurrence being experienced at its peak during the dry season.[12],[13] However, the epidemiological trend of occurrence and transmission in recent times has undergone an observed shift from being a seasonal outbreak to having occurrence and transmission taking place all year round; this can be corroborated with statistics from the year 2016 up till date (2018).

The following case definitions need to be considered when attempting to make a diagnosis of LF syndrome:[14],[15],[16],[17],[18]

  • A patient with a history of contact with rat urine and droppings or eating rats
  • All age groups are susceptible, including pregnant women who are more susceptible especially in the third trimester
  • Individuals such as family members, caretakers, traditional healers, having close contact with LF patient
  • Participants in a traditional burial rite with an LF patient within 3 weeks of the onset of their illness
  • Patients receiving health-care services from a provider who is also treating a known or suspected LF case
  • Sexual partner of a known or suspected LF case, since the virus can be present in semen for up to 3 months after clinical recovery.


It is worthy of note that early diagnosis is difficult, except there is a high index of suspicion. A detailed clinical examination and laboratory investigation are usually necessary.[19],[20] However, the incubation period for the disease is between 6 to 21 days.[7],[8],[21] Severity of illness may depend on a number of factors including the body's natural immune response,[21] mode of transmission,[22] duration of exposure,[23] infecting dose,[24] phase of illness in the contact case,[25] and degree of virulence of the Lassa virus strain involved.[26] Swollen face and neck, sore throat, high fever, myalgia, malaise, cough, bleeding from body orifices, and hearing loss are some of the nonspecific clinical features suggestive of LF.[27],[28]

The study was designed to disseminate a general public awareness message about the recent trend regarding the observed seasonal variation pattern in the epidemiological transmission, outbreak, and status of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria.


  Materials and Methods Top


Study area

Ondo State is one of the 36 states in Nigeria. It was created on February 3, 1976, and it has contributed immensely to the increase of the population in term of infrastructural development, economic, and social well-being. According to the Nigeria population census of 2006, Ondo State is populated with about 3.7 million people. Ondo State is an agrarian economy with over 45% of the population with agriculture being the dominant employer of labor but politically remains one of the most sophisticated and volatile in Nigeria. Although it is largely populated by the Yorubas, the hospitality, culture, and friendly weather make the place highly cosmopolitan. Ondo State lies between longitude 4°30' and East of the Greenwich Meridian 5°45' and 8°15' north of the Equator. This means that Ondo State lies entirely in the tropic. The climate is tropical with two distinct seasons: the rainy season (April–October) and the dry season (November–March). The temperature throughout the year ranges from 21°C to 39°C while humidity is relatively high. The annual rainfall varies from 2,000 mm in the Southern parts to 1,150 mm in the Northern area. The rainfall decreases in amount and distribution from the coast to hinterland. Ondo State generally enjoys luxuriant vegetation. A high forest zone (or rain forest) is found in the South while the Northern fringe is mostly sub-savannah forest. The state is bounded in the North by Ekiti and Kogi States, in the East by Edo State, in the West by Osun and Ogun States, and in the South by the Atlantic Ocean. Ondo State is made up of eighteen local government areas (LGAs) with 3 Geo-political zones of Ondo South, Ondo Central, and Ondo North. Akure city is the state capital and belongs to Ondo Central in the geopolitical zoning while it houses the State Specialist Hospital, Akure which serves as a referral center for lower level health facilities from the entire Ondo State and some neighboring states. The city of Akure is characterized by low level of public health management of wastes especially household and hospital's waste in the indigenous core areas characterized by high-density and low-income populations.

Study design

This was a retrospective observational longitudinal study carried out to report the recent trend regarding the observed seasonal variation pattern in the epidemiological transmission, outbreak and status of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria.

Data collection source

The data in this study were sourced and collected from the state epidemiological records on LF at the Department of Public Health Services, Epidemiology Unit, State Ministry of Health, Akure, Ondo State, Nigeria.

Ethical consideration

The ethical clearance for this study was obtained from the Health Research Ethical Committee of the State Ministry of Health, Akure, Ondo State, Nigeria. In addition, no unauthorized use of information was made as research data confidentiality was properly and adequately maintained in line with the World Health Organization international standard of practice.


  Results and Findings Top


As shown in [Figure 1], LF outbreak in the period under consideration showed an increasing trend, except in 2015 where the rate of seropositively infected and confirmed cases reduced by 62.5% (dropped from 8 to 3 cases). The rate of confirmed seropositive cases increased by 533.3% in 2016 compared to 2015, 300% in 2017 compared to 2016, and 19.7% increase in 2018 compared to 2017 events. [Figure 1] also shows the mortality rate recorded which was also directly dependent on the rate of confirmed seropositively infected cases; it was 50% in 2014, 0% in 2015, 63.1% in 2016, 23.6% in 2017, and 25.3% in 2018.
Figure 1: Graphical plot for the observed trend of Lassa fever seropositive confirmed cases and mortality cases between 2014 and 2018. Source: Department of public health services, epidemiology unit, state ministry of health, Akure, Ondo State, Nigeria

Click here to view


[Figure 2] shows an all year round LF disease outbreak in the year 2017 analyses. The peak of the disease outbreak in the year under consideration occurred in February (12 cases) and August (12 cases), and then followed by June (11 cases) and December (9 cases).
Figure 2: The trend of seropositive confirmed cases of Lassa fever outbreak in Ondo State, Nigeria between January 2017 and December 2017. Source: Department of public health services, epidemiology unit, state ministry of health, Akure, Ondo State, Nigeria

Click here to view


[Figure 3] showed the distribution pattern of LF outbreak in Ondo State, Nigeria, between January 2017 and December 2017. The highest seropositive cases were recorded in February (12 cases) and August (12 cases) and then followed by June (11 cases) and December (9 cases). Furthermore, the highest survivor cases were recorded in August (9 cases) and December (9 cases) and then followed by February (8 cases) and June (7 cases). In addition, the highest mortality cases were recorded in February (4 cases), June (4 cases), and August (4 cases), and then followed by January (3 cases) and July (3 cases).
Figure 3: The distribution pattern of Lassa fever outbreak in Ondo State, Nigeria between January 2017 and December 2017. Source: Department of public health services, epidemiology unit, state ministry of health, Akure, Ondo State, Nigeria

Click here to view



  Discussion Top


The concise explanations on the current trend of epidemiological outbreak pattern for LF in the state and the challenges peculiar to the outbreak give a detailed understanding of the persisting situations. The outbreak of the disease has been recurring since 2014 up till date (2018). This outbreak usually occurs in the Northern senatorial district of the adjacent state,[29],[30] precisely the LGAs such as Ose and Owo LGAs.[31] These are the LGAs that share boundary with Edo State, where the incidence and prevalence rates of LF outbreak has been recorded as the highest in the country at recent times.[32] Majority of the people in these LGAs are rural dwellers. Their major activities are farming, food processing, and marketing. Some of the foods processed by these people are naked local foodstuffs such as Garri, lafun, and pupuru (all from cassava). The local processing of these foodstuffs is usually unhygienic such that they get exposed and contaminated by rodents' excreta and others infectious agents.[33],[34] LF outbreak in the period under consideration showed an increasing trend, except in 2015 where the rate of seropositively infected and confirmed cases reduced by 62.5% (dropped from 8 to 3 cases). It is difficult to describe this reduction to some measures such as awareness, education, improved method of food processing and other measures because the upward trend started in the year 2016 and has continued to date. The rate of confirmed seropositive cases increased by 533.3% in 2016 compared to 2015, 300% in 2017 compared to 2016, and 19.7% increase in 2018 compared to 2017 events. The case fatality recorded was also directly related to the rate of confirmed seropositive infected cases. It was 50% in 2014, 0% in 2015, 63.1% in 2016, 23.6% in 2017, and 25.3% in 2018. The increasing trend of LF outbreak and death in Ondo State can be attributed to poverty, poor level of education, low level of disease transmission awareness, harmful religious beliefs and practices, poor public health law implementation, unhygienic food processing habits, poor funding of control measures, nonavailability of molecular laboratory diagnostic facilities, and shortage of infectious disease/public health specialists (clinical virologists/public health physicians) within the state to reduce turnaround time.[35],[36] The year 2017 analyses revealed that there was an all year round disease outbreak for LF in the state. This was contrary to the widely circulating postulation that LF outbreak is being influenced by dry seasons. The peak of the disease outbreak in the year 2017 occurred during February (12 cases) and August (12 cases), as this is the peak months of dry seasons and wet seasons, respectively, in Ondo State, Nigeria. In addition, the highest mortality cases were recorded in February (4 cases), June (4 cases), and August (4 cases) which are the peak months of dry seasons, mid-wet seasons, and wet seasons in Ondo State, Nigeria. This observation further supports the clinical notion that some underlying factors [35],[36] earlier mentioned as the critical and determinant factors responsible for the disease outbreak.

Challenges of containing Lassa fever outbreak in Ondo State

These important socioeconomic factors that pose serious challenges to the containment of LF outbreak in Ondo State, Nigeria are discussed as follows:[21],[22],[23],[24],[25],[26],[34],[37],[38]

Poverty

Poverty is the major causes of the outbreak in this part of the world because majority of people in these endemic areas live in slums and villages. They cannot afford good accommodations, and their living environment is not hygienic. This actually exposes them to rodents that contaminate their foodstuffs and get them infected with LF virus.[34],[37],[38]

Although data on poverty are many times controversial, this seems to be confirmed by the data provided by the United States Central Intelligence Agency's World factbook (CIA factbook), which stated that 70% of the Nigerian population lived below the poverty line.[34] The majority of the people in the state inhabit in rural communities where their living conditions are very poor. They live in poor accommodation environment where rodents can easily breed.

Emergence of new virulent mutant strains of Lassa mammarenavirus

There are also some degree of possibilities that these recurrent outbreaks of LF within ondo state and the affected neighboring states may be associated with the emergence of new mutant strains of Lassa mammarenavirus (LASV) that are highly pathogenic and virulent in nature. It will require sophisticated molecular diagnostic techniques and detailed genetic study of the virus in order to confirm this suspicion. As of this present moment, there are inadequate infrastructures, facilities and medical expertise put in place to carry out such research within the state and the entire Nigeria nation. We further advocate that the state government in conjunction with the federal government should put in place all the necessary infrastructures, facilities and appropriate medical expertise to enhance quick response to any LF outbreak and to prevent future recurrence within the state and the entire Nigeria nation.

Poor food handling habits

Some local foods such as fried cassava flour (gari) and sun-dried cassava flour (lafun) are usually processed in a very poor and unhygienic manner. For instance, gari, which is required to be heat dried, is semi-fried, and then sun-dried which in the process can get exposed to rodents and/or their excreta, some of which harbor Lassa virus. This practice is common in the southern berth of the state where LF is endemic.

Inadequate access to mass media publicity

It is a fact that the majority of the state population live in the rural areas. The southern berth of the state where LF is endemic is mostly inhabited by rural dwellers. These people have poor access to television, radio, newspaper, and other information communication mediums. This is linked with poverty, poor power/electricity supply, and low literacy level. Therefore, inhabitants are not able to access preventive information about LF.

Inadequate funding and limited facility for the treatment of Lassa fever patients

It usually requires a large sum of money to manage every Lassa patient successfully in terms of drugs, consumables, and laboratory diagnosis. The recent outbreak of 2018 presented a situation where drugs and other consumables were running out faster due to an overwhelming number of cases. The only treatment center in Federal Medical Center, Owo, was not enough because the facility was stretched beyond its limit during the 2018 outbreak.

Very low motivation and inadequate training of health-care workers

Most of the health workers and clinicians across the state are not properly sensitized on the case management protocols. This is evidenced by a report of cases that were discharged against medical advice from some hospitals in the state. There were a limited number of health caregivers to manage cases of LF at the treatment center in Federal Medical Center, Owo, Nigeria.

Recommendations

  • The government should create an intervention fund account for the management of disease outbreak to ensure the availability of fund to contain the disease
  • Government through the state ministry of health should intensify effort on masses educational awareness programs and community sensitization about LF outbreak
  • There should be continuous sensitization of clinicians and all health caregivers on the hospital protocols to manage LF patients
  • Government and partners should train more medical staffs on the treatment and management of viral hemorrhagic fevers
  • Government and all stakeholders should intensify effort to implement the existing environmental law against poor food handling, unhygienic, and poor sanitation
  • There should be an aggressive economic plans and social welfare to improve standards of living among the citizenries
  • Religious leaders must also be involved in the campaign for the containment of outbreaks for effective implementation and containment of the disease outbreak.



  Conclusion Top


The observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria, can be attributed the challenging poor socioeconomic factors and persistent situations peculiar to the outbreak such as poverty, inadequate access to mass media publicity, inadequate funding and limited facility for the treatment of LF patients, very low motivation and inadequate training of health-care workers, poor level of education, low level of disease transmission awareness, harmful religious beliefs and practices, poor public health law implementation, unhygienic food processing and handling habits, poor funding of control measures, nonavailability of molecular laboratory diagnostic facilities, and shortage of infectious disease/public health specialists (clinical virologists/public health physicians) within the state to reduce the epidemiological transmission and outbreak. The year 2017 analyses revealed that there was an all year round disease outbreak for LF in the state. This was contrary to the widely circulating report that LF outbreak is being influenced by dry seasons. The peak of the disease outbreak in the year 2017 occurred during February and August, as this is the peak months of dry seasons and wet seasons, respectively, in Ondo State, Nigeria.

Acknowledgment

We would like to thank all the staff at the Department of Public Health Services, State Ministry of Health, Akure, Ondo State, Nigeria, for their immense assistance during this study. Their support was of paramount importance to the completion of this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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