Chile officially recognised as the first country in the Americas to have eliminated Leprosy.

Chile has become the first country in the Americas to be recognised to have officially eliminated Leprosy, according to a press release issued by the World Health Organization on 4 March 2024. Chile is only the second country globally to reach this goal, following Jordan in September 2024. The conformation also makes Chile the sixth country in the Americas to have eliminated at least one Neglected Tropical Disease, joining Brazil, Colombia, Ecuador, Guatemala, and Mexico.

Chilean flags. Mark Scott Johnson/Wikimedia Commons.

Leprosy was first recorded in Chile on Rapa Nui (Easter Island) in the late nineteenth century, with some subsequent cases reported on the mainland. The last reported case of a person becoming infected with the disease on Chilean territory occurred on Rapa Nui in 1993. However, the country has continued widespread monitoring for Leprosy, with 47 cases reported between 2012 and 2023, all of which were acquired outside of the country, and all of which were successfully treated.

Leprosy is caused by the Bacteria Mycobacterium leprae and Mycobacterium lepromatosis. It is essentially a skin disease, with the Bacteria infecting patches of skin, which can become dry and itchy, lose their pigmentation, suffer skin thickening, nerve damage, and local immune system failure, which can cause the patches vulnerable to secondary infections by other Bacteria, Fungi, and Viruses. It is these secondary infections which cause the ulceration and tissue loss associated with the disease, which can lead to shortening or loss of fingers and toes, or even facial features. The nerve damage associated with the disease can cause patients to fail to notice wounds, making them more vulnerable to infection.

Mycobacterium leprae heavy load (6+) in Ziehl-Neelsen stained slit skin smear microscopy at a magnification of 2000X. Ajay Kumar Chaurasiya/Wikimedia Commons.

Leprosy is thought to be spread by mucus droplets exposed by through the mouth or nose (which can enable it to spread among children rapidly) but not through most other forms of contact; it is not sexually transmitted, and patients with HIV do not appear to be any more vulnerable, although malnutrition may be a factor. Much of the Human population appear to be naturally immune to Leprosy, with vulnerability to the disease being genetic, and tending to run in families, which can be problematic, particularly in poorer communities where people are living in cramped conditions and have trouble accessing medicine. 

Leprosy is a zoonotic disease, with wild reserves of the Bacteria found in a number of Animal species, including Primates such as the Chimpanzee, the Sooty Mangabey, and the Cynomolgus Macaque. In Europe is thought to have been spread by Red Squirrels, which are known to be vulnerable to the disease, and which were extensively hunted for their fur in the Middle Ages. The disease is thought to have been introduced to the Americas by European settlers, but has become established in there in Armadillos, which can act as a wild vector, spreading Leprosy back to Humans.

The first effective treatment for Leprosy was developed by Alice Augusta Ball, a young researcher at the College of Hawai'i (now the University of Hawai'i), in 1915 (Ball is also noted to have been the first African American woman to achieve a masters degree in chemistry, the first African American woman hired as a chemistry instructor at the College of Hawai'i, and possibly the first African American woman to publish an article in a major scientific journal). Today it is typically treated with a combination of antibiotics such as rifampicin, dapsone, and clofazimine, with other antibiotics available if resistance to these is encountered. Such treatments can typically eliminate the disease completely, although the courses of treatment are long (6-12 months) and involves taking multiple pills each day, which can be problematic, particularly in younger children.

Alice Augusta Ball in 1915. University of Hawai'i/Wikimedia Commons.

Leprosy is still considered to be endemic to 132 countries, with around 200 000 new cases reported each year. The worst affected countries are Brazil, India, and Indonesia, each of which typically reports more than 10 000 new cases each year. Twelve other countries, Bangladesh, Democratic Republic of the Congo, Ethiopia, Madagascar, Mozambique, Myanmar, Nepal, Nigeria, Philippines, Somalia, Sri Lanka and Tanzania, typically report between 1000  and 10 000 new cases per year, while another 117 countries typically report between 1 and 1000 cases per year. The World Health Organization is currently working towards the global elimination of Leprosy in partnership with the Swiss drug company Novartis, which provides multi-drug therapy for the disease to patients anywhere in the world at no cost, under the Partnership to Eliminate Leprosy scheme.

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Ongoing Diphtheria outbreak in Nigeria appears to be worsening.

Since the week ending 2 July 2023, Nigeria has recorded an unusual increase in cases of Diphtheria across several states, according to a press release issued by the World Health Organization on 13 September 2023. From 30 June to 31 August 2023, a total of 5898 suspected cases were reported from 59 Local Government Areas in 11 states. In week 34 (ending 27 August 2023), 234 suspected cases have been reported from 20 Local Government Areas in five states, with one laboratory confirmed case from the 22 samples collected. Eighteen of these cases were epidemiologically linked and 141 were classified as clinically compatible.

Diphtheria is a highly contagious vaccine-preventable disease caused mainly by the Bacterium Corynebacterium diphtheriae, a form of Mycobacterium, which can be fatal in 5-10% of cases, with a higher mortality rate in young children.

The World Health Organization's most recent risk assessment of the Diphtheria outbreak in Nigeria has maintained the risk as high at the national level, and low at the regional and global levels. Public health measures such as vaccination response, enhanced surveillance for early case detection, case management and risk communication coordinated by the Nigeria Centre for Disease Control, in collaboration with the World Health Organization and other partners, are being implemented in response to the outbreak.

Since 27 April 2023, Nigeria has reported suspected cases of Diphtheria weekly to the World Health Organization. However, between 30 June and 31 August 2023, the country recorded an unusual increase in the number of confirmed Diphtheria cases. From 30 June to 31 August 2023, a total of 5898 suspected cases were reported from 59 Local Government Areas in 11 states across the country. The majority (99.4%) of suspected cases were reported from Kano (1816), Katsina (234), Yobe (158), Bauchi (79), Kaduna (45) and Borno (33). 

Diphtheria cases by year/epidemic-week in Nigeria, 1 May 2022 – 27 August 2023. World Health Organization.

Of the cumulative 8353 suspected cases reported since the outbreak was first reported in 2022, 4717 (56.5%) cases were confirmed (lab confirmed (169; 3.6%), epidemiologically linked (117; 2.5%) and clinical compatibility (4431; 93.9%)). While 1857 (22.2%) were discarded as not compatible with Diphtheria, 1048 (12.5%) cases are pending classification and 731 (8.8%) cases had unknown diagnosis. The case fatality ratio dropped slightly from 6.7% before April 2023 to 6.1%. Of the 4717 confirmed cases, 3466 (73.5%) were aged 1 – 14 years, of these 699 were aged 0-4 years, 1505 aged 5-9 years, 1262 (aged 10 – 14 years. More than half of the cases (2656; 56.3%) were females. Only 1074 (22.8%) of the confirmed cases were fully vaccinated against diphtheria, 299 (6.3%) were partially vaccinated. More than half of the cases (2801; 59.4%) were unvaccinated.      

Definitive diagnosis through laboratory molecular testing identified Corynebacterium diphtheriae and Corynebacterium ulcerans isolates as the species driving this outbreak, particularly Corynebacterium diphtheriae as the major etiologic pathogen. Antibiotic susceptibility tests for 62 isolates of Corynebacterium diphtheriae have been carried out and the findings revealed that all isolates were resistant to penicillin, and most were resistant to trimethoprim-sulfathiazole and ciprofloxacin, while being susceptible to erythromycin. Thus, erythromycin became the drug of choice in the management of this outbreak.

Drug sensitivity results of toxigenic Corynebacterium diphtheriae isolated in Nigeria, May 2022 – July 2023. Nigeria Centre for Disease Control and Prevention/World Health Organization.

Diphtheria is a highly contagious vaccine-preventable disease caused mainly by Corynebacterium diphtheria but also by Corynebacterium ulcerans. It spreads between people mainly by direct contact or through the air via respiratory droplets. The disease can affect all age groups; however, unimmunized children are most at risk.

Symptoms often come on gradually, beginning with a sore throat and fever. In severe cases, the Bacteria produce a poison (toxin) that causes a thick grey or white patch at the back of throat. This can block the airways, making it hard to breathe or swallow, and also creates a barking cough. The neck may swell in part due to enlarged lymph nodes.

Treatment involves administering Diphtheria antitoxin as well as antibiotics. Vaccination against Diphtheria has been effective in reducing the mortality and morbidity from Diphtheria dramatically. Diphtheria is fatal in 5-10% of cases, with a higher mortality rate in young children. However, in settings with poor access to Diphtheria antitoxin, the case fatality ratio can be as high as 40%.

Nigeria has recorded Diphtheria outbreaks in the past, notably in 2011 and 2022. In 2023, a previous outbreak of Diphtheria was recorded between January and April 2023 affecting 21 of the 36 states and the Federal Capitol Territory.

Nigeria is currently facing a second wave of a Diphtheria outbreak after a first wave of the outbreak was recorded between epidemiological week 52, 2022 (1 January 2023) and week 20, 2023 (22 May 2023). There is an increase in the affected population with a rise in the number of confirmed cases and related deaths reported in epidemiological weeks 31-33. There is an increased risk of transmission, with clusters and outbreaks reported in newly affected Local Government Areas, with currently 27 Local Government Areas reporting one clinically compatible case in the last three reporting weeks relative to 15 Local Government Areas that had active case in the preceding three weeks.

The low national coverage (57%) of the Pentavalent vaccine administered in routine immunization, and the suboptimal vaccination coverage in the paediatric population, with 43% of the target population unvaccinated, underscores the risk of further spread and the accumulation of a critical mass of susceptible population in the country with sub-optimal herd or population immunity. Vaccine coverage of 80–85% must be maintained to ensure community protection.

This emphasizes the urgent need to strengthen Diphtheria vaccination coverage nationwide, especially in the most affected states, such as Kano. Additionally, particular attention is necessary for regions experiencing insecurity challenges, like the Northwest, as it hampers vaccine accessibility. Due to insecurity, especially in Northeast Nigeria, vaccination coverage remains suboptimal.

Diphtheria antitoxin supply is currently very constrained and insufficient to respond to current demands, as there is only a limited number of manufacturers and large outbreaks are being reported in different regions of the world.  The Nigeria Centre for Disease Control and Prevention, with support from World Health Organization and other partners have procured 10 050 Diphtheria antitoxin vials for case management in response to the outbreak.

Diphtheria outbreaks are underreported in Nigeria. According to the 2021 Nigeria Multiple Indicator Cluster Survey and National Immunization Coverage Survey, the third dose of pentavalent vaccine coverage was 57% in 2021.

The control of Diphtheria is based on primary prevention of disease by ensuring high population immunity through vaccination, and secondary prevention of spread by the rapid investigation of close contacts to ensure prompt treatment of those infected.

Epidemiological surveillance ensuring early detection of Diphtheria outbreaks should be in place in all countries, and all countries should have access to laboratory facilities for reliable identification of toxigenic Corynebacterium diphtheria. Adequate quantities of Diphtheria antitoxin should be available nationally or regionally for the medical management of cases.

Vaccination is key to preventing cases and outbreaks, and adequate clinical management involves administering Diphtheria anti-toxin to neutralize the toxin and antibiotics reducing complications and mortality.

The World Health Organization recommends early reporting and case management of suspected diphtheria cases to initiate the timely treatment of cases, and follow-up of contacts, and ensuring a supply of Dihphtheria antitoxin.

The World Health Organization also advises that healthcare settings where Diptheria cases are likely to be encountered apply standard precautions, with focus on hand hygiene, personal protective equipment and equipment and environmental cleaning and disinfection droplet and contact precautions (at all times). That during screening/triage, medical personnel immediately place patients with symptoms of Upper Respiratory Tract Infection in a separate area until examined, and, if multiple cases are suspected, these should be cohorted with patients with the same diagnosis. Isolation areas should be kept segregated from other patient-care areas. Hospitals and medical centres should one meter between patients, and keep patient care areas well ventilated. Where possible, medical personnel should avoid patient movement or transport out of isolation area. If movement is necessary out of isolation area, have patient use a medical mask and cover any wounds/lesions on patient’s body.

Case management should be carried out following the World Heath Organization guidelines. In addition, high-risk populations such as young children under five years of age, school children, the elderly, close contact with diphtheria cases, and healthcare workers should be vaccinated on a priority basis. A coordinated response and community engagement can support further transmission and control of the ongoing outbreak.

Prophylactic antibiotics (penicillin or erythromycin, dependent on drug sensitivity) are indicated for close contacts of confirmed cases for seven days. If the culture is positive for toxigenic Corynebacterium spp., then the contact should be treated as a case with an antibiotic course for two weeks (Diphtheria antitoxin is not needed for asymptomatic cases or cases without a pseudomembrane).

Although travellers do not have a special risk of Diphtheria infection, it is recommended that national authorities remind travellers going to areas with Diphtheria outbreaks to be appropriately vaccinated in accordance with the national vaccination scheme established in each country prior to travel. A booster dose is recommended if more than five years have passed since their last dose.

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Outbreak of Diphtheria in Nigeria claims 73 lives.

Since the beginning of 2023, 557 confirmed cases of Diphtheria have been detected in Nigeria, affecting 21 of the 36 states and the Federal Capital Territory. In December 2022, the Nigeria Centre for Disease Control and Prevention was notified of suspected Diphtheria outbreaks in Kano and Lagos States. From 14 May 2022 to 9 April 2023, 1439 suspected cases have been reported, of which 557 (39%) have been confirmed, including 73 deaths among the confirmed cases (a case fatality ratio of 13%), according to a press release issued by the World Health Organization on 27 April 2023. Nigeria has previously reported Diphtheria outbreaks, with the most significant reported in 2011 affecting the rural areas of Borno State, in the northeast of the country. Diphtheria is a highly contagious vaccine-preventable disease which spreads between people mainly by direct contact or through the air via respiratory droplets. The disease can affect all age groups, however unimmunized children are particular at risk. It is potentially fatal. The disease can be treated by administering Diphtheria antitoxin as well as antibiotics. Vaccination against Diphtheria has reduced the mortality and morbidity of Diphtheria dramatically.

The Nigeria Centre for Disease Control and Prevention was notified of suspected Diphtheria outbreaks in Kano and Lagos States on 1 December 2022. In January 2023, the number of confirmed cases increased, peaking at over 150 cases in epidemiological week 4 of 2023 (ending 28 January - an epidemiological week is a standardized method of counting weeks to allow for the comparison of data year after year); since then, a weekly decreasing trend has been observed. From 14 May 2022 to 9 April 2023, 1439, suspected Diphtheria cases were reported from 21 states in Nigeria, with the majority (83%) of cases reported from Kano (1188), Yobe (97), Katsina (61), Lagos (25), Sokoto (14) and Zamfara (13). Of the 1439 suspected cases, 557 (39%) were confirmed (51 laboratory-confirmed, 504 clinically compatible and two epidemiologically linked), 483 (34%) were discarded, and 399 (28%) are pending classification. Laboratory-confirmed cases were reported from Kano (45), Lagos (3), Kaduna (1), Katsina (1), and Osun (1) states. Among the 557 confirmed cases, 73 deaths were recorded, for a case fatality ratio of 13%. The case fatality ratio has dropped significantly since the beginning of the outbreak due to, among other factors, increased access to Diphtheria antitoxin.

Distribution of Diphtheria cases by state in Nigeria from epidemiological week 19, 2022 to epidemiological week 14, 2023. World Health Organization.

Nigeria had recorded diphtheria outbreaks in the past, but not on this scale. The most significant outbreak reported was between February and November 2011 in the rural areas of Borno State, north-eastern Nigeria, where 98 cases were reported. 

Diphtheria is a highly contagious vaccine-preventable disease caused by exotoxin-producing Mycobacterium Corynebacterium diphtheriae It spreads between people mainly by direct contact or through the air via respiratory droplets. The disease can affect all age groups, however unimmunized children are particular at risk. It is potentially fatal.  Symptoms often come on gradually, beginning with a sore throat and fever. In severe cases, the Bacteria produce a poison (toxin) that causes a thick grey or white patch at the back of throat. This can block the airways, making it hard to breathe or swallow, and also creates a barking cough. The neck may swell in part due to enlarged lymph nodes. Treatment involves administering Diphtheria antitoxin as well as antibiotics. Vaccination against Diphtheria has reduced the mortality and morbidity of diphtheria dramatically. Diphtheria is fatal in 5-10% of cases, with a higher mortality rate in young children. However, in settings with poor access to Diphtheria antitoxin, the case fatality ratio can be as high as 40%. 

Under the leadership of the Nigeria Centre for Disease Control and Prevention, coordination and monitoring of Diphtheria surveillance and response activities in the country are ongoing through the weekly Diphtheria National Technical Working Group meetings. Rapid Response Teams have been deployed to Katsina, Osun and Yobe States and re-deployed to Kano and Lagos States to support response activities. Harmonization of surveillance and laboratory data across states and laboratories is ongoing. Sensitization/training of clinical and surveillance officers has taken place in states where Rapid Response Teams have been deployed, on the presentation, prevention, and surveillance of Diphtheria. Cascaded training has been conducted in the effected states by some of the laboratory scientists/physicians trained at the Nigeria Centre for Disease Control and Prevention National Reference Laboratory in Abuja. Procurement for reagents and sample collection and transportation materials/media processes has been initiated. Drug sensitivity tests are ongoing at Nigeria Centre for Disease Control and Prevention National Reference Laboratory on isolates sent in from states. Distribution of Diphtheria antitoxin to the affected states has been ongoing since December 2022. Strengthening of routine immunization activities across the country continues. 

Diphtheria cases are under-reported in Nigeria, with few reports of outbreaks in the past. The last outbreak was reported between February and November 2011 in the village of Kimba and its surrounding settlements in Borno State, north-eastern Nigeria, where 98 cases were reported. The Diphtheria toxoid-containing vaccine third dose coverage in Nigeria is suboptimal. According to the 2021 Nigeria Multiple Indicator Cluster Survey and National Immunization Coverage Survey, the third dose of pentavalent vaccine coverage was 57% in 2021.

Distribution of Diphtheria cases by state in Nigeria from epidemiological week 19, 2022 to epidemiological week 14, 2023. World Health Organization.

The country is currently faced with several public health emergencies such as Lassa Fever, Cholera, Monkeypox, Meningitis and a humanitarian emergency in the northeast of the country. Due to insecurity, especially in north-eastern Nigeria, vaccination coverage remains suboptimal, especially in the areas controlled by non-state armed groups. Therefore, the outbreak of Diphtheria further complicates and strains the already overstretched resources. The global supply of Diphtheria antitoxin is limited, and this may affect the availability of the required doses in a timely manner.

The overall risk of Diphtheria in Nigeria was assessed as high at the national level, low at the regional level, and low at the global level.

The World Health Organization recommends that epidemiological surveillance ensuring early detection of Diphtheria outbreaks should be in place in all countries, and all countries should have access to laboratory facilities that allow for the reliable identification of toxigenic Corynebacterium diphtheriae. For the adequate medical management of cases, sufficient quantities of Diphtheria antitoxin should be available nationally or regionally.

The World Health Organization also recommends early reporting and management of suspected Diphtheria cases to initiate timely treatment of cases and follow-up of contacts and ensure the supply of diphtheria antitoxin. Case management should be carried out following the World Health Organization guideline and involve administering antitoxin to neutralize the toxin and antibiotics to kill the Bacteria, reducing complication and mortality.  

As vaccination is key to preventing cases and outbreaks, high-risk populations such as children under five years of age, schoolchildren, close contact of Diphtheria cases, and healthcare workers, should be vaccinated with Diphtheria-containing vaccines on a priority basis. A coordinated response and community engagement can support control of the ongoing outbreak.

Although travelers do not have a special risk of Diphtheria infection, it is recommended that national authorities remind travelers going to areas with Diphtheria outbreaks to be appropriately vaccinated in accordance with their national vaccination scheme. A booster dose is recommended if more than five years have passed since the last dose. The World Health Organization does not recommend any travel and/or trade restrictions to Nigeria based on the information available for this event.

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