Category: Diseases, Syndromes and Conditions

Categories : Diseases, Syndromes and Conditions Paediatrics

Limpopo Measles Outbreak Now 35 Cases amid Lower Vaccination Rates and Effectiveness

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Figure 1. The epidemiological curve of measles outbreak cases, Greater Sekhukhune and Mopani Districts, Limpopo province, September to November 2022 (*Two sporadic cases in Vhembe District are not included). Source: NICD

As of 10 November, the National Institute of Communicable Diseases reported 35 laboratory-confirmed measles cases in Limpopo, with 14 new cases on 8 and 9 November, all in Mopani district. Thus far, most of the laboratory-confirmed cases (25 of 35) fall within the 13 month to 9 year age range.

With these new cases, the Mopani district with 19 cases has overtaken the Greater Sekhukhune district which remains at 16 (see Figure 1). Only seven cases are known to be vaccinated; eight are either unvaccinated or partially vaccinated; vaccination status of the remaining 20 is unknown.

According to a recent study published in BMC Public Health, measles has been experiencing a resurgence in South Africa. Over 2015–16, measles had remained largely under the elimination target of under one case per million in South Africa, but rose above this threshold from 2017–2019. Cases fell below the threshold in 2020 with the onset of COVID, but the pandemic also saw normal vaccination efforts slipping. The article authors also noted a measles vaccine effectiveness of only 80% among 1–4 year olds, compared to the 95% rate found in large datasets.

Those cases reported in the Mopani district were in the Greater Giyani, Ba-Phalaborwa, and Ga-Kgapane sub-districts. Epidemiological investigations showed that in the Mopani district, two siblings with measles infection had contact with cases in the Greater Sekhukhune district when they travelled there for a family funeral.

While two cases were reported in Vhembe District, they were considered sporadic as they had not links to the other cases and are not included in the outbreak tally.

The laboratory-confirmed measles infections have been identified in 19 males and 16 females ranging in age from 6 months and 24 years in the Greater Sekhukhune district, while cases range from 2 to 42 years in the Mopani district (Table 1), with increasing cases in the 5–9 year age range. Two children were hospitalised but no deaths or other complications from measles have been reported.

According to the NICD, the affected districts are continuing with the public health response activities and tracing and vaccinating contacts.  Measles catch-up doses are also being given to children who have missed vaccinations.

Source: NICD

Categories : Diseases, Syndromes and ConditionsTags :

New Monoclonal Antibody Prevents Malaria Infection in African Adults

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Mosquito, a malaria parasite vector
Photo by Егор Камелев on Unsplash

One dose of a new monoclonal antibody safely protected healthy, non-pregnant adults from malaria infection during the malaria season in Mali. The antibody was up to 88.2% effective at preventing infection over a 24-week period, demonstrating for the first time that a monoclonal antibody can prevent malaria infection in an endemic region. These findings were published in The New England Journal of Medicine.

The only WHO-recommended vaccine against vaccine, RTS,S (Mosquirix), provides partial protection against clinical malaria during the early years of life when given to children aged 5 to 17 months in four doses over a 20-month period. Other drugs consisting of small chemical compounds that effectively prevent malaria infection are also available for infants and young children as well as travellers. The requirement for frequent dosing of these drugs can limit adherence, however, and the emergence of drug resistance may also limit their usefulness. Thus, there is an urgent need for new, fast-acting, infrequently dosed interventions that safely provide strong protection against malaria infection.

Malaria is caused by Plasmodium parasites, which mosquitos inject into into the skin and bloodstream in a form called sporozoites. These travel to the liver, where they mature and multiply before spreading throughout the body via the bloodstream to cause illness. P. falciparum is the Plasmodium species most likely to result in severe malaria infections, which, if not promptly treated, may lead to death.

The Phase 2 NIAID-USTTB trial evaluated the safety and efficacy of a one-time, intravenous infusion of a monoclonal antibody called CIS43LS. This antibody was previously shown to neutralise the sporozoites of P. falciparum in the skin and blood before they could infect liver cells. Researchers led by Robert A. Seder, MD, isolated a naturally occurring form of this antibody from the blood of a volunteer who had received an investigational malaria vaccine, and then modified the antibody to extend the length of time it would remain in the bloodstream.

The study team for the Phase 2 trial enrolled 369 healthy, non-pregnant adults aged 18 to 55 years in the rural communities of Kalifabougou and Torodo in Mali, where intense P. falciparum transmission typically occurs from July through December each year.

The first part of the trial assessed the safety of three different intravenous doses of CIS43LS – 5mg/kg of body weight, 10 mg/kg and 40 mg/kg – in 18 study participants, with six participants per dose level. The study team followed these participants for 24 weeks and found the antibody infusions were safe and well-tolerated.

The second part of the trial assessed the efficacy of two different doses of CIS43LS compared to a placebo. Three hundred and thirty participants were assigned at random to receive either 10mg/kg of the antibody, 40mg/kg, or a placebo by intravenous infusion. No one knew who was assigned to which group until the end of the trial. The study team followed these individuals for 24 weeks, testing their blood for P. falciparum weekly for the first 28 days and every two weeks thereafter. Any participant who developed symptomatic malaria during the trial received standard treatment from the study team.

The investigators analysed the efficacy of CIS43LS two ways. Based on the time to first P. falciparum infection over the 24-week study period, the high dose (40 mg/kg) of CIS43LS was 88.2% effective at preventing infection and the lower dose (10 mg/kg) was 75% effective. An analysis of the proportion of participants infected with P. falciparum at any time over the 24-week study period found the high dose was 76.7% at preventing infection and the lower dose was 54.2% effective.

“These first field results demonstrating that a monoclonal antibody safely provides high-level protection against intense malaria transmission in healthy adults pave the way for further studies to determine if such an intervention can prevent malaria infection in infants, children, and pregnant women,” Dr Seder said. “We hope monoclonal antibodies will transform malaria prevention in endemic regions.”

Dr Seder and colleagues have developed a second antimalarial monoclonal antibody, L9LS, that is much more potent than CIS43LS and therefore can be administered in a smaller dose as a more convenient subcutaneous injection. An early-phase NIAID trial of L9LS in the United States found that the antibody was safe and prevented malaria infection for 21 days in 15 out of 17 healthy adults exposed to P. falciparum in a carefully controlled setting. Two larger, NIAID-sponsored Phase 2 trials assessing the safety and efficacy of L9LS in infants, children and adults are underway in Mali and Kenya.

Source: NIH/National Institute of Allergy and Infectious Diseases

Categories : Cardiovascular Disease Diseases, Syndromes and ConditionsTags :

Study Reveals How Shingles Elevates the Risk of Stroke

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MRI images of the brain
Photo by Anna Shvets on Pexels

Scientists investigating why people who have had shingles have an increased stroke risk now believe the answer lies within, exosomes, lipid vesicles called that shuttle proteins and genetic information between cells. Their study, published The Journal of Infectious Diseases, details the mechanisms behind the link between shingles and strokes.

“Most people know about the painful rash associated with shingles, but they may not know that the risk of stroke is elevated for a year after infection,” said the study’s lead author Andrew Bubak, PhD, assistant research professor in the Department of Neurology at the University of Colorado School of Medicine. “Importantly, the rash is often completely healed and individuals feel normal but nonetheless are walking around with this significant elevation in stroke risk.”

Herpes zoster (HZ) or shingles is caused by the varicella zoster virus which causes chicken pox. The virus lingers in the ganglionic neurons and can reactivate, causing excruciating pain. But researchers have found that shingles can also increase the risk of stroke especially for those under age 40 where the shingles vaccine is not typically recommended.

The risk is greatest in people with the rashes on their faces, perhaps due to the proximity to the brain.

To better understand how this works, Bubak and his team began looking more closely at exosomes.

“Exosomes carry pathogenic cargo that can cause thrombosis and inflammation distant from site of actual infection,” Bubak said. “That could ultimately lead to a stroke in patients.”

Researchers collected plasma samples from 13 patients with shingles and 10 without. The samples were taken at time of infection and at 3-month follow-ups for a subset of patients and exosomes were extracted from the plasma.

The researchers found prothrombotic exosomes which could cause blood clots in those with the infection. They also discovered proinflammatory exosomes that also pose risks for stroke at the 3-month follow-up.

Bubak said the findings suggest that in a subset of people with shingles, the virus may not return to latency or the circulating exosomes that induce a prolonged prothrombotic state may persist even after therapy is done and the rash is gone. He said using antiviral agents longer with the addition of antiplatelet and anti-inflammatory agents could help.

“As well as initiatives to increase HZ vaccine uptake to decrease stroke risk, particularly in individuals with known preexisting stroke risk factors,” said Bubak. “If these findings are confirmed with a larger longitudinal study, then this could change clinical practice.”

Most physicians are unaware of the connection between shingles (which has an effective vaccine) and stroke.

“But it’s really important and so easily mitigated,” Bubak said. “Send them home with antiplatelet agents.”

Source: University of Colorado Anschutz Medical Campus

Categories : Diseases, Syndromes and Conditions General InterestTags :

Axial Spondyloarthritis Association of South Africa wins Excellence Award at EULAR PARE Assembly 2022

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Maranda Van Dam, Chairperson of ASASA (left) accepting award, with Souzi Makri President of PARE (middle) and Nikos Sleeks, ELEANA Greece (right)

Maranda van Dam, Chairman of the Axial Spondyloarthritis Association of South Africa (ASASA) won an award of excellence at the EULAR PARE (People with Arthritis/Rheumatism across Europe) Congress 2022, for work performed by ASASA around axial spondyloarthritis (AxSpA) in South Africa. The PARE congress took place from 20 – 22 October 2022, in Brussels, and included a Representation Committee consisting of members of the PARE, of which van Dam is an associate.

The award was based on strides made by ASASA towards improving the quality of life of people living with AxSpa, as well as training done to build awareness in the medical fraternity around AxSpA in the country. With 36 posters entered into the awards by organisations across the globe, ASASA came out tops.

When asked about the award, van Dam said, “This was a real honour to represent South Africa at PARE. 2022 is also the first year that an African country was invited to attend PARE. Winning this award sheds light on our country and our unique problems. The delay to diagnosis of 10.8 years is just unacceptable. The access to the correct medication in both the private and public sector is also not sufficient for a debilitating, progressive disease that can lead to disability if left untreated.”

ASASA estimates that there are approximately 160 000 people suffering from the AxSpA in South Africa, with many of these sufferers undiagnosed. ASASA has made significant strides this year in the training of over 100 General Practitioners and over 250 optometrists around AxSpA diagnosis and the effects it can have on other parts of the body, like the eyes. In addition, ASASA, along with other partners, assisted in gathering data from South African respondents in the first ever live patient survey, called the International Map of Axial Spondyloarthritis (IMAS) survey, which is run by the Axial Spondyloarthritis International Federation that surveys people diagnosed with AxSpA and assesses the impact and burden that AxSpA has on the lives of patients, from their perspective.

Van Dam concluded, “There is still a lot we can do in South Africa and ASASA is busy growing its team of volunteers to help to build awareness around AxSpA in the country. We aim to continue to build support structures for patients in the country, as well as continually working with the medical fraternity, assisting with early diagnosis and access to treatment.”

Categories : Diseases, Syndromes and ConditionsTags :

Training the Immune System to Accept Haemophilia A Treatment

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Source: CC0

Haemophilia A, the most common severe form of haemophilia, affects almost exclusively males and can usually be with factor VII injections, but not for all sufferers, as the immune system may treat the factor as an intruder. New research has uncovered an important immune mechanism that targets B cells, which is crucial in making the the therapy effective. The study is published online in the Journal of Clinical Investigation.

Haemophilia A patients have a defect in factor VIII, a protein key for clotting. Most patients therefore receive an intravenous injection of the functional clotting factor every few days as treatment. But frequently, and especially at the start of treatment, the immune system recognises the injected agent as foreign to the body and attacks it. This is the most serious complication of haemophilia treatment because factor VIII can then no longer work.

In these cases, immune tolerance therapy, which was also developed at the University Hospital Bonn (UKB) more than 40 years ago, often helps. This involves regularly injecting the haemophilia sufferers with a high dose of factor VIII over several months, letting the immune system learn to tolerate it. The underlying immune mechanisms are unknown. “However, this doesn’t always work,” explains Prof Dr Johannes Oldenburg at the UKB. “In about 30 percent of patients, tolerance induction does not lead to success. So your body’s own defences continue to attack and destroy the factor VIII protein, which means that factor VIII cannot be used for treatment. We wanted to know the reason for this.”

To this end, the team looked at two cell types in the immune system, B cells and regulatory T cells. B cells recognise foreign molecules in the body and produce antibodies against them, which switch off the function of the molecule. For factor VIII, this means that it is no longer effective in haemophilia treatment.

Brake in the immune system

Regulatory T cells moderate the strength and duration of the immune response. The researchers have now found a new type of Treg cell that can act specifically against certain B cells rather than the overall immune response. “We were able to show that immunotolerance therapy results in the generation of regulatory T cells that exclusively induce B cells against factor VIII to commit suicide,” says Dr Janine Becker-Gotot of the Institute of Molecular Medicine and Experimental Immunology (IMMEI) at UKB. “These T cells have a sensor that allows them to recognise and attach to the corresponding B cells. In addition, they have the ability to push the self-destruct button on the surface of B cells.”

This button is a molecule called PD-1 which, on activation, leads to apoptosis. Every active B cell has this button. “Our experiments enabled us for the first time to detect regulatory T cells that can activate this self-destruct button only in very specific B cells, in order to specifically prevent unwanted immune responses,” explains IMMEI Director Prof Dr Christian Kurts.

The more PD-1 buttons the B cells against factor VIII carry on their surface, the easier it is for them to be driven to suicide by immune tolerance therapy. “The amount of PD-1 varies from person to person,” Becker-Gotot explains. “If it’s very low to begin with, there’s a good chance that many inhibitor-producing B cells will survive and continue to neutralise the injected factor VIII.”

Test to show in whom immunotolerance therapy is useful

Interestingly, B cells also produce more PD-1 once they come into contact with regulatory T cells. “We can now test how strong this reaction is,” the researcher says. “If PD-1 levels go up shortly after starting immune tolerance therapy and then stay up, that’s a clear sign that the treatment is going to be successful.” The team is currently developing a blood test that can be used to detect whether or not immune tolerance therapy is working in patients during the prolonged treatment.

“Our findings have great basic scientific value,” explains Prof Kurts. “And not just for haemophilia, but also for other congenital disorders where missing proteins are replaced therapeutically. In the long term, they could also be used to develop new treatments.”

Source: University of Bonn

Categories : Diseases, Syndromes and Conditions VaccinesTags :

Limpopo Measles Outbreak Continues amid Low Vaccination Rates

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Photo by CDC on Unsplash

Since 11 October 2022, the National Institute for Communicable Diseases (NICD) seven measles cases have been detected in Greater Sekhukhune District in Limpopo province within 30 days, as of 21 October. 

Infected individuals ranged from 9 months to 24 years. One child was fully vaccinated for measles, with two measles doses given in 2019. One child was unvaccinated, and the other five measles cases had unknown vaccination history. One measles case was hospitalised while one other had a complication that led to pneumonia.

District and provincial health officials have started a public health response. This includes enhanced surveillance for measles, contact tracing, screening for suspected cases using a case definition followed by collection of blood and throat swabs for measles diagnostic testing, and reviewing medical records to pick up missed cases. Vaccinations are underway for those exposed to suspected or confirmed cases.

The measles immunisation coverage data for the Greater Sekhukhune district showed a decrease of 87% to 64% for measles dose 1 and 86% to 60% for measles dose 2 from 2017 to 2022. This is below the 95% coverage needed to achieve herd immunity. A survey is being done to validate the vaccination data provided to the province and investigate factors that might be contributing to the measles outbreak.  Community awareness and health promotion by healthcare workers is continuing in the district to inform the public about the spread of measles and interventions to prevent disease. Measles vaccination has been initiated for children under 15 years to increase the measles immunity in the community and to prevent further spread of measles.

Clinicians should continue to be on the alert for measles cases, especially in Limpopo Province, as large measles outbreaks are occurring in sub-Saharan Africa, including in neighbouring countries.

Signs and Symptoms

Measles is a highly contagious disease caused by a virus of the paromyxovirus family. Patients with measles present with fever and a rash. The rash looks like small, red, flat spots over the body. The rash does not form blisters, nor is it itchy or painful. Other signs include cough, conjunctivitis and coryza. Complications of measles can include diarrhoea, dehydration, encephalitis, blindness and death. Other measles complications are pneumonia, scarring of the cornea (kerato-conjunctivitis), and rarely encephalitis. Complications are more serious in very young children (under 2 years) or who are malnourished.

Clinicians and caregivers should check children’s road-to-health booklets to ensure measles vaccinations are up to date. Suspected measles cases should be notified on the NMC system. Click here to access the Case Notification form 

Source: NICD

Categories : Diseases, Syndromes and ConditionsTags :

Study Finds Wastewater Monitoring can Work for Most Pathogens

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Photo by Jan Antonin Kolar on Unsplash

Researchers in the American Journal of Epidemiology report that wastewater surveillance of diseases that infect humans should work in most cases. But more research is needed to apply the science for public health benefit, the research team concluded.

Led by epidemiologist David Larsen from Syracuse University, the team’s work published examined all peer-reviewed scientific articles of wastewater surveillance published through July 2020. The team identified a variety of pathogens that can be found in wastewater, including almost all infectious diseases that the World Health Organization has classified as a Public Health Emergency of International Concern (PHEIC) such as Ebola virus and Zika virus.

But despite this positive finding, few studies relate what is found in the wastewater to public health and the amount of disease that is circulating.

“Testing the wastewater is only one component of this powerful science,” said Dr Larsen, an associate professor of public health at Syracuse University. “Understanding the results and implications for public health is just as challenging. We need interdisciplinary teams working together to maximise the benefit of wastewater-based epidemiology.”

Wastewater-based epidemiology is the science of taking what is found in wastewater and using that information to understand population-level health trends. Most of the articles reviewed looked at what they could find in the wastewater and omitted the second step of relating the findings to other measures of population-level health, such as numbers of cases, test positivity, or hospitalisations.

Wastewater-based epidemiology of COVID has enjoyed substantial availability of clinical COVID data, and results from wastewater surveillance are more easily understood in terms of COVID transmission. However, the research team determined that more work is needed to be done for other pathogens, including monkeypox and polio, to increase the utility of wastewater surveillance to benefit public health.

Source: Syracuse University

Categories : Diseases, Syndromes and ConditionsTags :

Tofacitinib Could Treat Rare but Deadly Systemic Sclerosis

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Photo by Louise Reed on Unsplash

Systemic sclerosis, or scleroderma that affects the skin and internal organs, is one of the rarest autoimmune diseases, affecting roughly 100 000 people in the US, mostly women. It has the highest mortality rate among rheumatic diseases.

There are no licensed treatments available for this subset of scleroderma patients, and rheumatology researchers are constantly searching for opportunities to use resources and technology that have proven beneficial in treating other autoimmune and rheumatic diseases.

In a new study published in JCI Insight, researchers found that tofacitinib, a drug approved for rheumatoid arthritis, was well tolerated among patients with early systemic sclerosis, and discovered the drug primarily affected the protein, interferon, both in fibroblasts and keratinocytes cells.

Dinesh Khanna MBBS., MSc, director of the Michigan Medicine Scleroderma Program, explained: “We wanted to understand first, if there was any clinical benefit of tofacitinib to patients, but we were also asking, what are the differences in the cells of healthy skin versus systemic sclerosis cells…how does the drug work?”

The study sample size consisted of 15 patients with early diffuse cutaneous systemic sclerosis — patients with skin hardening and issues with organs. Of the total participants, 10 patients received 5mg of tofacitinib twice a day, and the remaining received placebo in a double-blind randomised placebo-controlled trial.

Over the course of the 24-week trial period, researchers found no patients who exhibited severe adverse effects at or before the trial ended. Measures included the modified Rodnan skin score (mRSS).

These results showed that the average mRSS score and other measures improved over the course of the trial. In addition, patients on placebo went on open label tofacitinib after 24 weeks and there was ongoing improvement during the next 24 weeks, indicating improvement in the measure.

“We are delighted to find that the drug is safe to use and can possibly be repurposed for systemic sclerosis treatment,” said Khanna, “but what made this study innovative was the use of single cell technology.”

Participants in the study had a skin biopsy at the start of the trial and then again six weeks after they received tofacitinib or placebo. Then, clinicians used the relatively new technology — single cell RNA sequencing — to watch the mechanism of tofacitinib at work in the trial participants’ skin cells.

“This work highlights the ability of single-cell RNA-sequencing to determine how disease states are maintained and how various cell populations in the skin, both fibroblasts, skin cells, and immune cells communicate, providing unparallelled power to address disease mechanisms, and how drugs, like tofacitinib, work in a disease where they have not previously been used,” said Johann Gudjonsson MD, PhD, professor of dermatology and a collaborator on this study.

Along with discovering how tofacitinib inhibits fibroblasts and keratinocytes, researchers found that the drug had minimal effect on T cells.

“Because we found that the drug was working on one part (the mechanism of fibroblasts and keratinocytes), we are now considering if we can combine tofacitinib with another drug with complementary mechanism in action, in order to treat early systemic sclerosis without causing toxicity,” explained Khanna.

To understand more about the drug, researchers will need to conduct a more robust study and trial to see if their recent discoveries hold true.

“From this combined effort between Michigan Medicine and University of Pittsburgh, we know that the drug is safe, and we know that the technology (RNA sequencing) is feasible, now we can start to utilise the technology and find out what type of therapies we can mix and match that will add benefit to patients,” Khanna said.

Source: Michigan Medicine – University of Michigan

Categories : Diseases, Syndromes and Conditions Metabolic DisordersTags :

Strong Link of Type 1 Diabetes to Enterovirus Infection

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A 3D map of the islets in the human pancreas. Source: Wikimedia

A meta-analysis of molecular studies found a strong link between enterovirus infection and type 1 diabetes. Across 48 abstracts on the topic, people with type 1 diabetes were nearly eight times more likely to have an enterovirus infection than those with normal pancreatic function, according to a presentation at the European Association for the Study of Diabetes (EASD) meeting.

For this review, researchers examined 56 studies using molecular methods to identify enterovirus infection by looking for viral nucleic acid or protein in a human clinical sample.

People with islet autoimmunity were twice as likely to have had an enterovirus infection at any point in time, based on data from 18 studies.

Subgroup analysis of people who were diagnosed with the enterovirus within the past month found 16.22-fold higher odds of recent-onset type 1 diabetes, based upon 28 studies.

“This is very recent onset type 1 diabetes, and that was the highest risk group that we detected,” reported Sonia Isaacs, PhD candidate, of University of New South Wales in Australia, during a press conference.

Looking more closely at other subgroup criteria revealed associations.

First, those who had any islet autoimmunity and eventually progressed to full-blown type 1 diabetes were over five times more likely to have an enterovirus infection than controls; this was a higher risk than those who had islet autoimmunity and never progressed to type 1 diabetes. When it came to timing, only infections at the time of or after islet autoimmunity seroconversion carried higher risk (OR 5.1), whereas the increased risk wasn’t significant for infections prior to seroconversion.

Isaacs noted that those with a familial risk of type 1 diabetes (ie in a first-degree relative) also had a much higher risk for an enterovirus infection (OR 9.8), higher than the subgroup recruited for having a high-risk HLA gene. Those who had the high-risk HLA gene and a familiar risk of type 1 diabetes had 141.1-times higher odds of prior enterovirus infection.

Having several enterovirus infections was also linked with a doubled chance of islet autoimmunity.

Specific type of enterovirus linked to risk of type 1 diabetes included:

  • Enterovirus A: OR 3.7
  • Enterovirus B: OR 12.7
  • Enterovirus C: OR 13.8

“This is where the coxsackieviruses come from,” Isaacs pointed out. “Coxsackievirus B1 and B4 stood out.”

Isaacs suggested the possibility of enterovirus vaccinations and antivirals as a prevention strategy for type 1 diabetes.

Source: MedPage Today

Categories : Diseases, Syndromes and Conditions Environmental EffectsTags :

Lassa Virus Endemic Area may Grow in Coming Decades

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Pictured are projections of the ecological niche suitability for Lassa virus based on climate models and other data. Credit: Scripps Research and University of Brussels

Analysing decades of environmental data associated with Lassa virus outbreaks, researchers projected that areas hospitable to Lassa virus spread may extend from West Africa into Central and East Africa in the next several decades. With this expansion and expected African population growth, the human population living in the areas where the virus should theoretically be able to circulate may rise by more than 600 million.

“Our analysis shows how climate, land use, and population changes in the next 50 years could dramatically increase the risk of Lassa fever in Africa,” says first author Raphaëlle Klitting, PhD, a postdoctoral researcher at Scripps Research during the study, which is published in Nature Communications.

Lassa virus is a zoonotic pathogen found in the Natal multimammate rat (Mastomys natalensis), most likely transmitted to humans via its droppings. While an estimated 80% of infections are mild or asymptomatic, the remaining cases are more severe, with signs and symptoms that can include haemorrhaging from the mouth and gut, hypotension, and potentially permanent hearing loss. Mortality rate in hospitalised patients can be up to 80%.

An estimated several hundred thousand infections occur each year, chiefly in Nigeria and several other West African countries. So far there is no approved vaccine or highly effective drug treatment.

Although the primary animal reservoir for Lassa virus is known, the virus spreads in only a subset of the areas where the animal is found. Thus, it is possible that environmental factors also help determine whether and where significant viral transmission can occur. In the study, the researchers developed an ‘ecological niche’ model of Lassa virus transmission, using environmental data at sites of known spread.

Combining the model with projections of climate and land-use changes in Africa in the next several decades, as well as the known range of the Natal multimammate rat, the researchers estimated the areas of Africa that could support Lassa virus transmission currently, and in the years 2030, 2050, and 2070. The projected current areas corresponded well to known endemic areas in West Africa, but the estimates for future decades suggested a vast expansion within and beyond West Africa.

“We found that several regions will likely become ecologically suitable for virus spread in Central Africa, including in Cameroon and the Democratic Republic of the Congo, and even in East Africa, in Uganda,” Klitting said.

Currently Africa’s population is undergoing rapid growth; the researchers therefore considered projections of this population growth for the areas of current and potential future Lassa virus circulation. They found that the number of people potentially exposed to the virus could increase from about 92 million today to 453 million by 2050, and 700 million by 2070 – an increase of over 600%.

More hopefully, the researchers examined the dynamics of the spread of Lassa virus using data on sequenced viral genomes sampled at various locations in West Africa and found that virus dispersal appeared to be slow. They concluded that, unless transmission dynamics change drastically in the new location where the virus circulates, the virus’s spread into new ecologically suitable areas in the coming decades may also be slow.

The authors say that the findings should inform African public health policies, for example, by encouraging officials to add Lassa virus to lists of viruses under epidemiologic surveillance in parts of Central and East Africa.

“With the ongoing climate change and increasing impact of human activities on the environment, further comprehensive studies of the ecology and spread of zoonotic and vector-borne diseases are needed to anticipate possible future changes in their distribution as well as their impact on public health,” said senior author Simon Dellicour, PhD, of the University of Brussels.

Source: Scripps Research Institute