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Archive for the ‘Epidemiology’ Category

HERD IMMUNITY AND COVID-19

By Dr. Stephen A. Berger

Herd immunity concept. People of different age groups, men, women and children are protected from the harmful effects of viruses. Preventive measures, human protection, group immunity.

WHAT IS HERD IMMUNITY?

It stands to reason that a contagious disease should disappear from a population when a sufficient percentage of potential victims – “the herd” has become immune. This outcome may arise because a massive number of individuals have been either infected or vaccinated.

Most authorities dealing with COVID-19 have set the goal for herd immunity at >60 percent; however, the precise percentage for any infectious disease will depend on many factors involving demography, virulence, route of infection, etc. 

 

HAS AN INFECTIOUS DISEASE EVER BEEN ERADICATED BY REACHING HERD IMMUNITY?

Infectious Diseases have been known to reach herd immunity, however, none have been permanently eradicated by it. For instance, although there was an observed decrease of measles infections during the 1930s, recent outbreaks indicate the disease is far from being eliminated – despite effective vaccination measures introduced in 1963.

 

IMPORTANT CONSIDERATIONS

As many countries enter into a second-wave of this pandemic, the bottom-line question for those who advocate the achievement of herd immunity through mass infection of the population will be one of cost-benefit. 

This prompts a few thoughts and questions. Any program to actively infect large numbers of individuals will begin with the isolation of the elderly and other high-risk populations. How many countries are truly equipped to house, feed, isolate, and treat millions of people in these categories? Do they have the manpower, physical structure, and funding?

It is important to note that the 2002-2004 SARS outbreak was not brought to an end by herd immunity, but rather through stringent public health methods implemented by affected countries. 

 

HOW MUCH TIME WILL BE REQUIRED TO ACHIEVE HERD IMMUNITY?

My country (Israel) has a population of 8.8 million and is currently experiencing 1,000 to 2,000 new cases per day. If we allow the current disease rate to continue, it will take perhaps three more years (!) to exceed 60 percent immunity. 

Would the Health System – already at capacity – be able to sustain all of this? Is there proof that COVID-19 infection even leads to immunity?  In what percentage of patients? Does immunity persist for more than a year or two?  Will immunity also “cover” newer strains of coronavirus?

Several COVID-19 vaccines will be released for general use in the next three to six months. Assuming that these vaccines are effective, targeted mass-infection at this point will cause more harm than good… and at best be a case of “too little, too late.”

 

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Let’s end Polio

An Egyptian stele thought to represent a polio victim. 18th Dynasty (1403–1365 BC).
An Egyptian stele thought to represent a polio victim. 18th Dynasty (1403–1365 BC).

 

Poliomyelitis dates back to ancient times, as captured in this 14th century BC Egyptian carving, detailing a typical symptom of atrophy in one or more of the limbs. 

The modern name is directly derived from Ancient Greek, poliós meaning ‘grey’ and myelós meaning ‘marrow’, the latter signifying the effect on the grey matter of the spinal cord.

But while the ancient Egyptians and Greeks knew about the disease, it wasn’t clinically described until the late 18th century (AD), by the English doctor Michael Underwood. The disease was finally ‘formalized’ in the 19th century, thanks to the work of physicians Jakob Heine, who completed the first study on the disease, and Karl Oskar Medin, the first to detail the epidemic nature of Poliomyelitis. This led to the illness often being referred to as Heine-Medin disease.

SYMPTOMS

Polio is highly infectious and is spread through the fecal-oral exchange, mainly affecting children under the age of 5 but adult cases are not uncommon. Symptoms include fever, sore throat, headache, vomiting, and still neck.

Although the disease is feared for its more extreme outcomes, such as paralysis, these develop in only 1-2% of all cases. Less than 10% of cases are fatal, with as most infections being asymptomatic.

CAMPAIGN TO END POLIO

It is unknown how many deaths Polio has caused through the ages, but a significant global campaign has been in place since the 1950s as a response to the epidemic in the United States. 294,094 cases were reported from 1944 to 1953; 108,159 from 1954 to 1963; and 514 from 1964 to 1973. The campaign, combined with the effective vaccine, has led to the country being declared polio-free in 1979.

The establishment of the Global Polio Eradication Initiative (GPEI) in 1988 had a huge impact on the fight to end polio.  Over 2.5 billion children were vaccinated since then, with 20 million volunteers in 200 countries taking part in the campaign.

Fantastic progress has been made with wild cases dramatically reducing from an estimated global incidence of 350,000 in 1988 to only 33 reported cases in 2018 – but the work isn’t over yet. The infectious nature of the disease could easily lead to extensive outbreaks and see the numbers increase again, despite the effective vaccine, as has been recently observed with measles. 

Although Type 2 has not been detected since 1999, nine outbreaks of vaccine-strain virus infection were reported since the OPV2 withdrawal in 2016, posing a threat to its complete eradication. The last reported case of Type 3 was in Nigeria, back in November 2012.

 

Polio cases worldwide, 1996-today. GIDEON.
Wild polio cases worldwide, 1996 – today, GIDEON.

 

Now is the time for the final push to limit the disease to the history books (and databases). If you want to be a part of the solution, head over to End Polio Now and get involved! It could make the world of difference to those affected.

 

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Hepatitis A in the United States

Liver Infection with hepatitis viruses - 3d illustration

 

Few Americans are aware of a major epidemic that has taken hold of large areas of their country in recent years – by a disease that is easily diagnosed and prevented. Sadly, public – and even professional interest in these events have been overshadowed by COVID-19.   

AN UPTICK IN CASES

Hepatitis A had been largely under control until three years ago and can be easily prevented through the use of a safe and effective vaccine. 

From January 2017 to January 2019, at least 26 separate outbreaks were reported, to a total of 11,628 cases and 99 deaths, nationwide. Homeless individuals and users of illicit drugs accounted for a large percentage of these patients. 

The graph below shows that the number of reported cases, which had been declining steadily since 1997, has taken a dramatic upturn during the current epidemic. 

 

Hepatitis A cases in the United States, 1947 - today
Hepatitis A cases in the United States, 1947 – today

 

As of September 2020, more than 1,000 cases have now been reported in each of seven states: Florida, Georgia, Indiana, Kentucky, Ohio, Tennessee, and West Virginia. Indeed, the total number of cases reported since the arrival of COVID-19 in the United States has reached 6,650 (to October 10, 2020)  – a major concern to public health specialists.

 

WHAT ARE THE SYMPTOMS?

Hepatitis A is a highly contagious disease that affects the liver. Infection may cause symptoms such as vomiting, jaundice, anorexia, dark urine, and light stools, occasionally accompanied by rash or arthritis. Symptoms normally persist between two to eight weeks, although the illness may last longer and be more severe in patients with underlying conditions.

The case-fatality rate of Hepatitis A ranges from 0.15% to 2.7%, with children faring better than adults.

 

SUPPORTIVE THERAPY IS THE ONLY TREATMENT

At the time of writing, there is no known cure for Hepatitis A. To speed up recovery, it is recommended that patients get plenty of rest and avoid substances that may have adverse effects on the liver, such as alcoholic beverages and certain medications.

 

WHAT IS THE DIFFERENCE BETWEEN HEPATITIS A, B, AND C?

Even though there is no drug therapy against Hepatitis A, it is less dangerous than Hepatitis B and C.

While most Hepatitis A patients recover with lifelong immunity to the disease, Hepatitis B and C may ‘reappear’ in the form of hepatic cirrhosis or hepatocellular carcinoma years after the acute illness. 

Hepatitis B is responsible for 60% to 80% of the world’s primary liver cancer cases. Thankfully, its rates continue to decline in  the United States:

Hepatitis B cases in the United States, 1966 - today graph
Hepatitis B cases in the United States, 1966 – today

 

The mode of transmission also differs among the three viruses. HepA is transmitted via the fecal-oral route, HepB, and HepC through the exchange of infected bodily fluids. 

As of 1998, injecting-drug abuse accounts for 60% of Hepatitis C transmission in the United States:

Hepatitis C cases in the United States, 1992 - today graph
Hepatitis C cases in the United States, 1992 – today

 

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Disease names – what do they mean?

Medical dictionary with disease names

In the midst of the continuing pandemic, World Dictionary Day seems like the perfect occasion to consider the meaning and origin behind some of the most well-known disease names. We’ve been speaking with Dr. Steve Berger, our co-founder, to learn more.

CORONAVIRUSES

Let’s start with the obvious one. COVID 19, which began as a localized outbreak of “Novel Coronavirus” infection,  is now a name almost every household in the world will know. COVID-19 comes from COrona VIrus Disease which first appeared in 2019, with the disease itself being caused by the SARS-CoV-2 virus.

SARS was a prominent name back in the early 2000s, with a simpler acronym Severe Acute Respiratory Syndrome. 

The names of COVID-19 and SARS-CoV-2 have been used throughout mainstream media, but not without a certain degree of confusion, which is similar to the one sometimes seen with HIV and AIDS. A useful analogy is that the Human Immunodeficiency Virus (HIV) causes Acquired Immunodeficiency Syndrome (AIDS) much like SARS-CoV-2 causes COVID-19.

A lesser-known fact outside of the medical community is that there are many different species of a type of virus. Each type is given a name derived from the kind of virus it is and often its discovery whereabouts. As of 2020, seven coronavirus species have been associated with human disease:   

  •       HCoV 229E 
  •       HCoV OC43 
  •       SARS-CoV 
  •       HCoV NL63 (New Haven coronavirus) 
  •       HCoV HKU1 
  •       MERS-CoV (the Middle East Respiratory Syndrome coronavirus) 
  •       SARS-CoV-2 

 

TYPES OF DISEASE NAMES

Not all diseases are given acronyms and the discordance between the name of the virus and the name of the disease is unusual. In many cases, viruses that infect humans are named for the disease that they cause. For example, poliomyelitis is caused by the poliomyelitis virus, while influenza is caused by the influenza virus. 

Disease names themselves are typically taken from either the area of the body it affects, or where it was discovered, or who discovered it. 

For instance, poliovirus’s name is derived from the Ancient Greek poliós, meaning grey, as it attacks nerve cells located in the grey matter at the center of the spinal cord. Influenza originates from the Italian term for influence. It was believed the illness was caused by ill omens from the sky, just as it was thought that another infectious disease, malaria, was caused by foul swamp air (mala aria).

Even the current pandemic has symbolic origins for its name, as the virus resembles a crown (Latin, corona) under the electron microscope. Similarly, rotavirus, a common cause of childhood diarrhea, resembles small wheels (Latin, rota). 

The Ebola disease, on the other hand, takes its name from the village it was first discovered, near the Ebola River in the Democratic Republic of Congo in 1976. Likewise, the West Nile virus was first identified in the West Nile District of Uganda in 1937; and the Zika virus in the Zika Forest of Uganda during the 1940s. Two of the coronaviruses identified this year are named after the places they were first reported in: New Haven, Connecticut, and the Middle East. 

 

A DOUBLE-EDGED SWORD

The naming of a pathogen for the region it was discovered can be stigmatizing and have geopolitical ramifications. The World Health Organization made a point to exclude the terms “Wuhan” and “China” when naming the current pandemic disease. Even the naming of disease after the discovering professional, or in someone else’s honor can be considered contentious, as is the case with Listeria. 

Listeria, found in contaminated food, was named after Joseph Lister, who pioneered hospital health standards throughout his career. He championed the use of early antiseptics, and even such novel ideas as washing hands… Imagine needing to justify the benefits of cleanliness in a hospital! However, during his career, Lister was shunned for his approach despite proving it hugely successful in preventing surgical mortality. 

Would you consider it an honor to have your name immortalized in the naming of a species, even if it is a bacteria? 

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“Under the radar” – Ongoing Lassa Fever Outbreak

By Dr. Stephen A. Berger

Stethoscope on Africa map
Nigeria is battling the largest recorded Lassa Fever outbreak to-date

 

Lassa Fever in Nigeria is a paradigm for Infectious Disease outbreaks that continue to threaten massive populations “under the radar” during the COVID-19 pandemic. As of October 3, 2020, a total of 1,112 fatal cases of COVID-19 had been reported in Nigeria.

In terms of population size, the statistical likelihood of dying from this disease in Nigeria – or in Singapore – is exactly the same. But then…nobody in Singapore is dying these days from Lassa Fever.    

WHAT IS LASSA FEVER?

The disease was first recognized in 1969, in northeastern Nigeria. The virus is acquired from African rodents and their secretions, primarily the Multimammate rat (Mastomys natalensis) which is its natural reservoir. A secondary person-to-person transmission can occur through contact with infected bodily fluids.

The illness is characterized by fever, pharyngitis, headache, chest pain, and diarrhea. 

Leukopenia, proteinuria, and hepatic dysfunction may also be present. Permanent hearing loss is common – indeed, this disease is the most common cause of acquired deafness in West Africa. Reported case-fatality rates range between 15-25%.

Multimammate rat (Mastomys natalensis)
Multimammate rat (Mastomys natalensis), a reservoir of Lassa Fever

DISTRIBUTION

It is estimated that as many as 500,000 individuals are infected in West Africa each year, resulting in 5,000 deaths. During the past 50 years, at least 88 travelers have returned home to other countries with this disease – including 11 importations into the United States. 

An ongoing outbreak of Lassa Fever continues in Nigeria well into 2020 – with 5,527 cases (222 fatal) reported as of August 16…all against the background of COVID-19.

Lassa Fever outbreaks map 2018-2020
Recent outbreaks map, 2018-2020, GIDEON

 

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Monkeypox

By Dr. Stephen A. Berger

 

Cynomolgus monkey, a known reservoir of the Monkeypox virus
Cynomolgus monkey, a known reservoir of the Monkeypox virus

 

WHAT IS MONKEYPOX?

Monkeypox, as the name implies, is a disease of monkeys (unlike chickenpox – which has no relation to chickens). Although the condition is reported in a group of eleven African countries, the virus was first discovered in a laboratory in Denmark in 1958, when it was first isolated from cynomolgus monkeys.

The signs and symptoms are similar to those of smallpox. Following a three-day prodrome of fever, headache, myalgia, and back pain, patients develop a papular rash in the face, extremities, and genitals. The rash then spreads outward to involve the face, with lesions evolving into umbilicated pustules. 

Unlike smallpox, death from monkeypox is relatively uncommon – five-to-ten percent.

Palms of a monkeypox patient
This 1997 image was created during an investigation into an outbreak in the Democratic Republic of the Congo (DRC) and depicts the palms of a monkeypox case-patient. It is important to note how similar this maculopapular rash appears to be when compared to the rash of smallpox, also an Orthopoxvirus. Image courtesy of CDC/Dr. Brian W.J.Mahy

NOTABLE OUTBREAKS

During the single year of 1967, almost eleven thousand cases occurred in West and Central Africa. 

The most unusual outbreak of monkeypox occurred in 2003 when 81 humans in the American Midwest were infected through contact with infected prairie dogs – themselves infected by rodents that had been imported from Ghana. Fortunately, all patients recovered without sequelae. By coincidence, the iconic outbreak of SARS was also reported at this time – perhaps, as in the current COVID-19 pandemic, distracting media attention from events surrounding other diseases. 

During 2018 to 2019, five Nigerian travelers were found to have monkeypox – in Israel, Singapore, and London. 

 

A RECENT RISE IN CASES

The viruses of monkeypox and smallpox are biologically similar. Indeed an attack of one will immunize the patient against the other. Thus, rates of monkeypox were low during the period that smallpox vaccination was widely used in Africa, while the discontinuation of vaccination has been followed by a resurgence of monkeypox cases. 

These developments are well illustrated by an ongoing outbreak of monkeypox that has persisted well into the COVID-19 pandemic. From January 1 to September 13, a total of 4,494 cases of monkeypox (171 fatal) were reported in the Democratic Republic of Congo.

 

Monkeypox cases in the Democratic Republic of Congo
Cases in the Democratic Republic of Congo, 1970 – 2019

 

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Rabies – a dumb disease

Vaccine Rabies Bottle and Syringe Needle Hypodermic Injection,Immunization rabies and Dog Animal Diseases,Medical Concept with Dog blurred Background.Selective Focus Vaccine vial
Dog vaccination programs are the most effective way to prevent Rabies

 

Rabies is endemic to over 150 countries, and according to the World Health Organization, 99% of all transmissions to humans are from dogs, potentially bringing into question the animal’s status as the ‘man’s best friend’. 

In Europe, southern Africa, and parts of North America, most cases are acquired from wild carnivores; mongooses, and vampire bats in Latin America and the Caribbean. In more recent years, humans have acquired rabies from inhalation of aerosols in bat caves, ingestion of dogs and cats for food, ticks, cart-scratches, and inadvertent transplantation of corneas or internal organs from infected donors. 

In recognition of World Rabies Day, we have asked our co-founder, Dr. Stephen Berger, for his take on the disease. He didn’t hold back with the assessment!

“Rabies, from an evolutionary standpoint, is a truly “stupid” disease. Most animals with Rabies virus infection become paralyzed and die – thereby preventing the survival and reproduction of the virus itself. Ebola and Smallpox, albeit highly contagious, are also “stupid” in this respect,” said Dr. Berger, highlighting an interesting point.

When a disease limits its access to new hosts, how does it survive and continue to spread?

How long before it’s too late?

Virus transmission takes place via exposure to infected saliva, not necessarily a bite –  although bites are the most common means of transmission. The virus is very active in moist conditions but quickly becomes non-infectious when dried or exposed to direct sunlight.

In dogs, the virus incubates for between 2 weeks to 4 months before the animal can transmit the disease.

In human cases, the incubation period can be as short as a few days or take as long as a few months for the disease to become active and symptoms to show.  In rare cases, Rabies has appeared as long as five years following an animal bite.  Once symptoms appear, the case-fatality rate is virtually 100%. As of 2014, only 13 cases of human survival from rabies had been documented.

Two forms of Rabies

The disease has two recognized forms – Furious and Paralytic, also known as ‘dumb Rabies’. In the furious form, dogs (or humans) froth at the mouth and display extreme hyperactivity. Patients often develop spasms when exposed to water – thus the term “hydrophobia.”  In some cases, a similar response will follow fanning the patient – “aerophobia.”

While Furious Rabies is most familiar to the lay public (thanks to the cinema and TV)  the Paralytic form often predominates among dogs. This type causes a slow progression from difficulty swallowing to full-body paralysis and eventually, death.

Rabies is 100% vaccine-preventable

When compared to diseases such as Tuberculosis, where symptoms such as coughing actively support transmission through the projection of infectious material into the air, Rabies would seem easier to control, especially when effective preventative and therapeutic vaccines and immune-globulins are available. 

The disease was recorded as far back as 556 BC, in China, and a viable vaccine has existed since 1885. The World Health Organization (WHO) considers the disease to be one of the Neglected Tropical Diseases, in part due to the under-usage of effective vaccination, which works even after the virus has entered the body.  A lesser-known adjunct to therapy is vitally important, but not as well-known to the public. Thorough cleansing of a wound using soap and water has been shown to reduce the incidence of Rabies by 50% following the bite of a rabid animal!

Sadly, despite the fact that 29 million people receive the vaccine every year, thousands still die from the disease. 95% of deaths occur in Asia and Africa, with children under the age of 15 making up 40% of all cases. 

Stray dogs present a significant problem in countries such as India, Namibia, Angola, Mozambique, and Kenya, where annual disease rates exceed 0.2 per 100,000 population.

WHO leads a collective “United Against Rabies” campaign to drive progress towards zero human deaths from dog-mediated Rabies by 2030.

Rabies distribution and outbreaks map, 1709 - 2020
Rabies distribution and outbreaks map, 1709 – 2020

 

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Brucellosis – how dangerous is it?

Set of different dairy products isolated on white
Brucellosis is most frequently transmitted via unpasteurized dairy products

 

Zoonotic diseases seem to be keeping the world on its toes. What is the disease responsible for the latest outbreak in China and what is its pathogenic potential?

Not the next COVID-19

Brucellosis is a category B bioterror disease, as classed by CDC. While it is one of the most important zoonotic diseases worldwide, brucellosis has limited pandemic potential, since human-to-human transmission is sporadic and occurs via blood, sexual exposure, or breastfeeding. 

63% of cross-border events since 1965 were directly linked to the consumption of unpasteurized dairy products. The largest ever reported outbreak took place in the province of Ghardaia, Algeria, in 2016. During that time, 819 cases were recorded – health authorities suspected consumption of raw milk and a popular traditional cheese “Kamaria” may have been to blame. Epizootics (outbreaks among animals) can be much larger.  Over 40,000 cattle acquired the disease during an outbreak in Spain in 2010. 

 

Brucellosis outbreaks and distribution map, 1938 - 2019
Brucellosis outbreaks and distribution map, 1938 – 2019

 

What are the symptoms of Brucellosis?

Initial symptoms include fever, sweats, and pain in muscles and joints;  while protracted infections may involve the heart valves, liver, or testicles.

Occupational hazard

The outbreak in China occurred among biopharmaceutical plant workers; and several prior disease clusters have involved workers in hospital laboratories.  For this reason, individuals working with Brucella must be especially careful when handling this pathogen.

For instance, in 2007, a biodefence laboratory in the United States was closed after workers were exposed to two bioterror agents: Brucella (agent of Brucellosis) and Coxiella burnetii (agent of Q fever).  Fortunately, this incident did not result in an actual outbreak. Professionals working in such environments are well-prepared for the possibility of similar scenarios and will likely behave in a way that minimizes any risks to public health. 

Interested in learning more? Check out our ebook Brucellosis: Global Status for the latest epidemiological data, clinical findings, and potential use in bioterrorism. The ebook includes 175 graphs and 1,977 references. 

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Streptomyces – the smell of life

The Mall in Central Park, New York City in late autumn on rainy day
The Mall in Central Park, New York City in late autumn on a rainy day

 

Did you know that humans can detect the smell of wet soil 200,000 times better than sharks sense blood? [1] It appears our olfactory abilities are not that bad after all, at least when it comes to finding potential sources of food. Petrichor, the term to describe the scent was coined in 1964, by scientists I. Bear and R.G. Thomas, meaning “petros” – stone and “ichor” – the blood of the gods [2] in Greek.

Divine or not, Streptomyces is a genus of over 800 bacterial species and subspecies responsible for the earthy smell of Autumn we know and love. But could it be that our innate senses are drawn to wet dirt for more reasons than farming? 

 

Could eating dirt cure the plague?

That is yet to be tested, but Streptomyces are certainly fit for more purposes than poetic walks after the rain. They are the most important source of antibiotics [3].

What is an antibiotic? By definition, it is a substance produced by one organism that is capable of inhibiting the growth or destroying other organisms  – a direct translation from Greek would be ‘anti-life’. In nature, this yields Streptomyces a competitive advantage. Astonishingly, they are responsible for nearly two-thirds of natural antibiotics [4].

For instance, Streptomyces griseus produces Streptomycin, the first antibiotic against tuberculosis, and a drug of choice against the agent of Plague Yersinia pestis, along with other 28 pathogenic bacteria species [5].  Streptomyces avermitilis helps keep parasites in check with its potent avermectins, and Chloramphenicol – a drug effective against 92 pathogens, is produced by Streptomyces venezuelae.

Streptomyces glaucescens under a microscope
Image of Streptomyces glaucescens. Courtesy of Tobias Kieser, John Innes Centre

 

Mavericks of the Streptomyces family

Although these species are not considered to be important agents of infection, it is worth noting that not all Streptomyces bacteria are friends of humanity, however. Two rebels, Streptomyces somaliensis and Streptomyces sudanensis go against the grain by infecting people’s feet with actinomycotic mycetoma.

First described as ‘Madura foot’ in 1842, the disease is thought to date back to the Byzantine period and typically presents as cutaneous and subcutaneous tissue swelling, thickening, or painless nodule involving feet 80% of the time [6].

Mycetoma global distribution map
Mycetoma global distribution map, GIDEON. Dark blue color indicates recent reports of autochthonous cases.

 

Although bacterial mycetoma is endemic throughout the tropical world, S. somaliensis and S. sudanensis are only found in Eastern Africa, as names indicate. In other parts of the world, S.albus has been known to occasionally rear its head [7] in skin infections, although such occurrences are very rare. 

And here’s the most fascinating fact – a distant ‘cousin’ of these pathogens, Streptomyces cattleya is an effective carbapenem used to treat Streptomyces spp. infections. A family feud in all its glory!

 

Why are bacteria named as fungi?

Streptomyces are about 450 million years old. Despite being a genus of bacteria, they are misleadingly suffixed with ‘-myces’, which stands for ‘fungi’ in Greek. This is because the first known example of the species contained branching filaments [8], a characteristic common to fungi.

Other actinobacteria, such as Mycobacteria and Actinomyces bear similar morphological features and thus carry a badge of mushroom in their names. Mycoplasmata – elusive gram-unidentifiable bacteria called ‘fungus form’, were named so by A. B. Frank in 1889. He thought ‘the “infection threads” of the organism were hyphae, and he knew of no hyphal-forming bacteria’ [9].

 

Want to learn more about Streptomyces? Try GIDEON ebook Guide to Medically Important Bacteria, 20% off on our website.

Interested in Mycetoma? Take a look at Mycetoma: Global Status

 

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References:

[1] H. Campbell, “Geosmin: Why We Like The Smell Of Air After A Storm”, American Council on Science and Health, 2018. [Online]. Available: https://www.acsh.org/news/2018/07/28/geosmin-why-we-smell-air-after-storm-13240. [Accessed: 11- Sep- 2020].

[2] I. BEAR and R. THOMAS, “Nature of Argillaceous Odour”, Nature, vol. 201, no. 4923, pp. 993-995, 1964. Available: 10.1038/201993a0 [Accessed 11 September 2020].

[3] K. Chater, “Streptomyces”, Brenner’s Encyclopedia of Genetics, pp. 565-567, 2013. Available: 10.1016/b978-0-12-374984-0.01483-2 [Accessed 11 September 2020].

[4] A. Hasani, A. Kariminik and K. Issazadeh, “Streptomycetes: Characteristics and Their Antimicrobial Activities”, International Journal of Advanced Biological and Biomedical Research, vol. 2, no. 1, pp. 63-75, 2014. Available: http://www.ijabbr.com/article_7033_7733c8235876d7ba635f6c831a916648.pdf. [Accessed 11 September 2020].

[5] “Streptomycin”, App.gideononline.com, 2020. [Online]. Available: https://app.gideononline.com/explore/drugs/20910. [Accessed: 11- Sep- 2020].

[6] V. Lichon and A. Khachemoune, “Mycetoma”, American Journal of Clinical Dermatology, vol. 7, no. 5, pp. 315-321, 2006. Available: 10.2165/00128071-200607050-00005 [Accessed 11 September 2020].

[7] M. Martin, A. Manteca, M. Castillo, F. Vazquez and F. Mendez, “Streptomyces albus Isolated from a Human Actinomycetoma and Characterized by Molecular Techniques”, Journal of Clinical Microbiology, vol. 42, no. 12, pp. 5957-5960, 2004. Available: 10.1128/jcm.42.12.5957-5960.2004 [Accessed 11 September 2020].

[8] K. Chater, “Streptomycesinside-out: a new perspective on the bacteria that provide us with antibiotics”, Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 361, no. 1469, pp. 761-768, 2006. Available: 10.1098/rstb.2005.1758 [Accessed 12 September 2020].

[9] C. Krass and M. Gardner, “Etymology of the term Mycoplasma”, INTERNATIONAL JOURNAL of SYSTEMATIC BACTERIOLOGY, vol. 23, no. 1, pp. 62-64, 1973. Available: https://www.microbiologyresearch.org/docserver/fulltext/ijsem/23/1/ijs-23-1-62.pdf. [Accessed 12 September 2020].

Mosquito: more than a bug

Anopheles mosquito sucking blood
Anopheles mosquito, a vector of Malaria

 

In one half of the world, the mosquito is seen to most as a minor annoyance, but for others, mosquitoes are synonymous with disease, pain, and death. Today is the World Mosquito Day and the perfect reminder of the devastating impact of such diseases as MalariaZika, and various kinds of Encephalitis for which mosquitoes are a major vector.

Malaria – a headline disease

Malaria is the headline disease associated with mosquitoes and it was on this very day in 1897 that Sir Ronald Ross discovered that female mosquitoes can transmit malaria between humans. This was a major breakthrough in tackling the disease, yet despite significant progress, over 100 years on it is still the cause of tens of thousands of deaths every year, with annual case numbers on a steady incline.

Worldwide Malaria cases graph Worldwide Malaria deaths graph

‘Bad Air’ of the ancients

Malaria dates back thousands of years. Ancestral evidence found in 30-million-year-old amber shows that mosquitoes plagued humans from the earliest civilizations. It started having a significant impact on human survival roughly 10,000 years ago at the start of agriculture, and even Cleopatra is reputed to have slept under a mosquito net – though likely to avoid bites in general, rather than a preventative measure for the disease. Given the disease’s age, it is no surprise it has been referenced under many different names, such as Roman Fever and ‘Bad Air’ (Mal Aria), from which the modern name is derived.

A brief history of drugs

The most effective early drug was centered around Quinine, known since the 16th century and made from ground cinchona “fever” tree bark. Successfully synthesized in the early 20th century, it is the precursor to such drugs as Chloroquine. The revolutionary Methylene Blue – first synthetic antimalarial – was developed by Heinrich Caro. It helped differentiate between blood cells and the nuclei of malarial parasites. In a world without advanced microscopes, this was a significant breakthrough in identifying the disease.

Prevention is better than cure

The prevalence of the disease led to many efforts to try and prevent infection, but it wasn’t until Sir Ross proved the female mosquito as the vector in 1897 that targeted efforts could be made in limiting contact to mosquitoes, along with improving medicines. Nowadays, mosquito nets, insect repellents, and regular anti-insect medicines are commonplace in homes across the globe. The killing of mosquitoes was even cited as a selling point for the ill-fated insecticide DDT.

The United States was certified as “malaria-free” by the World Health Organisation in 1970, but even so over 1,000 cases are reported every year, virtually all imported from other countries.

Malaria cases in United States graph

While it is a preventable and curable disease, it is worth taking extra protection measures when traveling to high-risk areas, such as central Africa or India. A combination of symptoms such as headache, back pain, chills, sweating, myalgia, nausea, vomiting can be unpleasant, to say the least!

Malaria worldwide endemic distribution map

 

Get 50% off Malaria: Global Status 2020 ebook

Interested in learning more? Love a good deal? In addition to this spotlight blog we are offering 50% off our latest Malaria: Global Status ebook, which is a fantastic opportunity to get access to the up-to-date distribution map, global and country statuses, and a more detailed breakdown of the epidemiology. Use coupon code ‘mosquito‘ at the checkout. The promotion ends on 27th August.

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