Every year, Nigeria battles numerous communicable diseases, some of which are vaccine-preventable and on the national priority list for eradication.

Due to the tropical climate, population density and migration, Nigeria is constantly faced with several public health emergencies which led to the death of scores of persons. Top on the list of such ailments recorded are Lassa fever, Yellow fever, Measles, Cholera, Cerebrospinal Meningitis among others.

PREMIUM TIMES analyses how Nigeria fared in 2019 in the surveillance, prevention, control and management of seven diseases that are on the top priority list of the agency in charge of disease control in Nigeria (NCDC).

1. Lassa fever - Lassa fever remains a public health challenge in West Africa with Nigeria bearing the highest burden. Since the beginning of 2019, 166 persons have died from Lassa fever in Nigeria.

The disease occurs throughout the year but peaks during the dry season (November to May).

According to the situation report from the Nigeria Centre for Disease control, from January 1 to December 8, 2019, 4820 suspected cases have been reported from 23 states. More cases were expected to be reported as the year runs to an end with two suspected cases already reported in Ebonyi State.

Although Nigeria was in the news negatively last year as the Lassa fever outbreak in the country reached the highest ever in the history of the disease, the number of deaths as at the time of this report were five less than last year.

According to 2018 epidemiological report for week 52, the death toll for Lassa fever outbreak was 171. From January 1 to December 31, 2018, a total of 3498 suspected cases were reported from 23 states. Of these, 633 were confirmed positive, 20 probable and 2853 negative (not a case) and Case Fatality Rate in confirmed cases is 27.0 per cent.

Though the agency is yet to have the total figure for 2019, from January 1 to December 8, 2019, a total of 4820 suspected cases have been reported from 23 states. Of these, 806 were confirmed positive, 19 probable, 166 deaths in confirmed cases and 3995 negatives (not a case) and Case Fatality Rate in confirmed cases is 20.6 per cent.

This year, there was an increase in the number of suspected cases and confirmed cases compared to last year. Although, the number of deaths is still significantly high; the agency had declared an early state of emergency on Lassa fever this year. The emergency period lasted from January 22 to May 26.

Though the emergency was declared over in May, reports showed that cases were still being reported.

In the reporting week 49, 13 new confirmed cases were reported. These include 11 from Ondo, one from Bauchi and one from Gombe, Also four deaths were recorded in this period, three from Ondo and one from Gombe.

Rats used to illustrate the story.

In 2019, 23 states - Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Plateau, Taraba, Adamawa, Gombe, Kaduna, Kwara, Benue, Rivers, Kogi, Enugu, Imo, Delta, Oyo, Kebbi, Cross River, Zamfara, Lagos and Abia - recorded at least one confirmed case across 86 Local Government Areas.

The Director-General of NCDC, Chikwe Ihekweazu, said last year that the spike could be due to increased surveillance and case tracing of contacts.

On response, NCDC said the Lassa fever national multi-partner, multi-agency Technical Working Group (TWG) continues to coordinate response activities at all levels.

2. Yellow Fever - Since September 2017 when the first case of yellow fever was rediscovered in Kwara State, the country has been recording cases of the disease.

This year, there has been a high record of suspected cases and death from the disease.

Since the beginning of this year, 47 persons have died from Yellow fever in Nigeria.

According to NCDC, between January 1 to December 27, Nigeria recorded 193 confirmed positive cases and 47 deaths were reported from 38 local governments in 15 states and the FCT.

Although there have been pockets of outbreaks in states across the country since 2017, the number of deaths recorded by week 49 of this year is higher than the same period in 2018.

Reports from NCDC show that from week 1 to week 49 of 2019, 47 deaths have been recorded as compared to same time 2018 when just one death was recorded.

Yellow fever is a vaccine-preventable disease. Unfortunately, the low immunization rate in the country has been a major contributing factor to the increasing prevalence of the disease in the country.

The yellow fever vaccination was introduced in Nigeria in 2004 as one of the routine vaccines expected to be given to children during routine immunisation. In spite of this, the country is still witnessing outbreaks of the disease.

The most recent outbreak was reported in September, which caused about 30 deaths. It started from a town in Bauchi State and was transmitted to Borno State and Kano State before the necessary intervention to curb the disease was initiated by the government and international donors. The outbreak and transmission are the largest recorded this year. All the other outbreaks had been in pockets and mainly contained in the locality where it was detected.

Other states which witnessed pocket cases or reported at least a case were Ebonyi, Cross River, Benue, Gombe, Sokoto, Kastina, Yobe, Kwara, Kogi, Osun, Edo among others.

In response, the federal government and international partners have conducted yellow fever reactive vaccination campaigns in many states across the country, especially in places where cases have been reported.

3. Cholera - This year, Nigeria witnessed a drastic drop in cholera cases in the country. This could be largely connected to the immunisation campaign conducted by the government and international partners in cholera hotspots across the country.

Nigeria through Gavi, the Vaccine Alliance, had benefited from the rollout of nearly 18 million doses of Oral Cholera Vaccine (OCV) which were shipped to 11 countries in 2018.

Cholera is an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae.

It affects both children and adults and can kill within hours if left untreated.

NCDC figures for epidemiological week 49 shows that from January 1 to December 8, a total of 3,499 suspected cases were reported with 595 confirmed cases and 71 deaths reported. Some of the states where cholera incidence and deaths were reported are Ogun, Adamawa, Bauchi, Kastina among others.

This is far lower than what was obtained in the same reporting week of 2018 where the number of suspected cases was 50,662, with 956 confirmed cases and 1135 deaths.

If Nigeria can continue with the trend of reduction in cholera cases in the country, it might be able to achieve the 2030 Global Roadmap aimed to reduce cholera deaths by 90 per cent and eliminate transmission in up to 20 countries.

The Director-General, World Health Organisation, Tedros Ghebreyesus, said in the 2018 global cholera report that "the decrease in several major cholera-endemic countries demonstrates increased engagement of countries."

Mr Ghebreyesus said the result shows the vital role of mass cholera vaccination campaigns.

"We continue to emphasise, however, that the long-term solution toward ending cholera lies in increasing access to clean drinking water and providing adequate sanitation and hygiene," he said.

4. Measles - There was a spike in cases of measles in Nigeria this year as 289 deaths occurred from the disease.

Data from NCDC indicated that 58,916 suspected cases with 2767 cases confirmed positive and 289 deaths were reported as at December 8.

WHO in its global measles report for 2019 said the eradication of the disease has suffered a setback globally as many countries have been reporting spikes of the disease.

This is largely attributed to vaccine hesitancy and low immunisation coverage in many countries of which Nigeria is one such country - with only 33 per cent immunisation coverage.

Measles is a vaccine-preventable communicable disease; unfortunately, Nigeria and the world are struggling to eradicate it. Though the vaccine is safe and cost-effective, there were over 110,000 measles deaths globally, mostly among children under the age of five.

WHO advised routine measles vaccination for children, combined with mass immunisation campaigns so as to reduce the global death from the disease.

5. Cerebrospinal meningitis - Since the beginning of the year, 103 people have died from cerebrospinal meningitis in Nigeria. The number of deaths recorded from the disease has been on a decline as compared to last year and the previous year.

Although Nigeria is currently at the beginning of a new Cerebrospinal Meningitis season, some state governments are beginning to administer vaccination as a precautionary measure to check the burden of the disease.

The disease which is synonymous with the dry season starts in December and peaks around March and April before subsiding in June/July every year. Nigeria had carried out a massive vaccination exercise during the 2017/2018 outbreak which claimed the lives of over 1,000 persons.

This vaccination exercise seems to be paying off as the epidemiological report from NCDC indicates that between January 1 and December 8, 2019, a total of 2770 suspected cases with 126 confirmed cases and 103 deaths were reported.

Though numbers of cases are expected to increase with the meningitis season, so far, the cases reported are lower when compared with 4466 suspected cases, 318 confirmed cases and 360 deaths reported during the same period in 2018.

With the new meningitis season approaching, the epidemiological report in the reporting week said there were nine suspected Cerebrospinal Meningitis (CSM) cases reported from five LGAs in three states (Adamawa 2, Cross River 4, and Katsina 3) with no laboratory confirmation or death recorded.

In preparation for the meningitis season, NCDC said the National CSM Technical Working Group (TWG) meets weekly to review reports from states and plans appropriately and surveillance has been enhanced in all states (with focus in states at higher risk)

6. Polio - Nigeria recorded no case of Wild Polio Virus (WPV) in the country. With this, Nigeria reached a milestone of three years without any incidence of the disease reported. If the status quo remains till March 2020, Nigeria will join the league of wild polio-free countries. If this happens, there is a possibility that Africa may be certified WPV free in 2020.

Procedures and verification processes are already ongoing for Nigeria to get a polio-free certification. However, all hands still need to be on deck in order to sustain the achievement.

A recent statement from the WHO Twenty-Third IHR Emergency Committee Regarding the International Spread of Poliovirus commended the strong efforts made by Nigeria to reach inaccessible and trapped children in Borno State even in the face of increased insecurity.

While the certification of WPV3 eradication was welcomed by the committee and underlines that polioviruses can be eradicated, concerns have been about another form of poliovirus, circulating vaccine-derived polio virus (cVDP) which is beginning to circulate in the country.

The virus has been reported in some states across the country. Vaccine-Derived polio (CvDpv2) outbreak has been largely due to poor routine immunisation and environmental sanitation. The strain of the virus is being isolated from environmental samples, as well as refuse dump sites and drainages.

To curtail a future problem of cVDPV2 in Nigeria, the government needs to increase its routine immunisation campaign and continually raise awareness on the dangers of the disease.

Monkeypox victim used to illustrate the story [Photo: Outbreak News Today]

7. Monkeypox - Monkeypox in the country was on the low this year as only two deaths were reported from the disease.

From January 1 to December 8, 116 suspected cases and 44 confirmed cases were reported in nine states (Bayelsa, Lagos, Delta, Rivers, Akwa Ibom, Enugu, Anambra, Cross River, and Oyo). Two deaths were recorded.

There was no significant difference in the data for this year as compared with 2018.

While there was no major outbreak of the disease in the country when compared to two years ago, the disease poses as an international threat as cases are being exported from Nigeria to other countries.

Monkeypox is mostly transmitted to people from wild animals, but human to human transmission also occurs. The disease can be contracted if an individual comes in contact with lesions, body fluids, respiratory droplets and contaminated materials of an infected person.

According to WHO, the smallpox vaccine can protect against monkeypox. The agency has approved a new third-generation vaccine - vaccinia vaccine - for the prevention of smallpox and monkeypox. Antiviral agents are also being developed.