Evolution of a pandemic: Coronaviruses to COVID-19

Coronavirus is not an exclusive finding of 2020 though it has been projected as “Novel Coronavirus” (nCoV). The so called nCoV has been designated as etiological agent of “Coronavirus Disease-2019” (COVID-19) that took shape of pandemic with its epicenter at Wuhan City of Hubei Province of China. Bovine and avian Coronaviruses are known since 1976 and a lot of research has already been done on their structure and pathogenicity.

The well characterized members of coronavirus family are positive-stranded RNA viruses. Coronaviruses possess a single-stranded, non-segmented, polyadenylated infectious RNA genome. The size of viral particles (virions) vary from 80-120 nm in diameter. Nanometer (nm) is ultra-small unit of measurement of length. There are one billion (1000,000,000) nanometers in a meter. These viruses could only be revealed through Transmission Electron Microscope (TEM) or Scanning Electron Microscope (SEM). Coronaviruses have pleomorphic look due to 10-20 nm long surface peplomers. Coronaviruses can cause diarrhea, hepatitis and bronchitis in lower mammals and birds. Three species of coronavirus are known to cause hepatitis in mice and seven species of coronavirus are known to cause bronchitis in birds.

Species of coronaviruses are characterized on the bases of molecular weight of surface polypeptides (glycoproteins). The molecular weight of surface glycoproteins of coronaviruses could be ranging from 15,000 to 200,000. They possess a large genome of 5x10⁶ to 8x10⁶ molecular weight. Massive research work has been done on coronaviruses in various virology laboratories all over the world to ascertain their genomic structure.

In the year 2002 “Severe Acute Respiratory Syndrome (SARS) was caused in humans by avian coronavirus (SARS-CoV). The animal reservoir of this coronavirus was perhaps bats. The avian coronavirus spread to other animals like cats and first infected humans in the Guangdong Province of southern China in 2002. An epidemic of SARS-CoV affected 26 countries in 2002-2003 and >8000 cases were reported as per World Health Organization (WHO). The transmission of SARS-CoV is primarily from human to human in the second week of disease due to excretion of viruses in respiratory secretions. So, infection spreads trough droplets of nasal secretion.

The current pandemic with Coronavirus has deliberately been given new nomenclature due to its genomic distinction from SARS-CoV known earlier. This new type of coronavirus causing SARS is called 2019-nCoV.

Symptoms of disease:

Symptoms of COVID-19 are like influenza and include fever, headache, shivering (rigors), myalgia, malaise, cough and sometimes diarrhea also. Fever is most frequently reported symptom, but it may be absent in initial stage especially in elderly and immunocompromised patients.

Cough may be dry initially with shortness of breath. Fever and diarrhea may progress in second week of disease. Elderly and people with associated illnesses like diabetes, hypertension, heart disease or organ transplant, may need special care to protect themselves from COVID-19.

Personal protection measures:

There is no immuno-prophylaxis for nCoV as vaccines are still under development. Personal hygiene, exercise and protein rich diet and vitamin-C are key to avoid coronavirus infection. Fresh fruits or juices rich in vitamin-C, high protein diet, coffee drinks, frequent drinking of warm water could be of great help to keep away COVID-19.

Frequent washing of hands with soap and water. Hand sanitization, wearing of face mask and maintaining physical distance (social distance) of approximately 6 feet would be of great help to avoid 2019-nCoV.

The need of the hour is not to panic but to follow the instructions and guidelines issued by local and national health authorities.

Diagnostic criterion:

Real Time - Reverse Transcription - Polymerase Chain Reaction (Real Time RT-PCR) is the only specific investigation to ascertain 2019-nCoV infection. The Chinese authorities isolated a new type of coronavirus from patients of outbreak of pneumonia in Wuhan City during laboratory investigations on 7^th January 2020 and named it 2019-nCoV.  Nasopharyngeal or oropharyngeal swabs are taken from suspected persons and transported to Laboratories in specially constituted transportation medium.

The principle of RT-PCR detection method is based on ‘Fluorogenic 5’ Nucleage Assay’. During the PCR reaction, the DNA polymerase cleaves the probe at 5’ end and separates the reporter dye from quencher dye only when the probe hybridizes to the target DNA. This cleavage results in the fluorescent signal generated by the cleaved reporter dye, which is monitored almost Real-Time by PCR detection system.

Warnings:

1.      This assay needs to be carried out by skilled personnel only.

2.      Clinical samples should be treated as highly infectious and samples should be prepared in biosafe laminar flow hoods.

3.      Do not use the kit after its expiry date.

4.      Carry out the test as per global standard procedure only.

5.      Avoid repeated freezing and thawing of reagents.

Care and treatment of infected persons:

Infected patients should be managed as per conditions. Patients should be home quarantined or admitted to COVID-19 Hospitals, as per clinical assessment. Symptomatic treatment should be started immediately.  Every patient needs to be instructed to wear face mask and wash/sanitize his/her hands frequently and maintain physical distance from other family members and friends. Proper counselling needs to be provided to patients with adequate supply of diet recommended by nutritionist. Health professionals need to wear ‘personal protection equipment’ (PPE) with adequate sanitization to avoid any cross infection.

Enforcement measures by administration:

Lockdown of public transport, schools, colleges, universities, offices and places of worships may be needed to restrict community transmission and spread of COVID-19. Medical infrastructure needs to be upgraded efficiently for optimum treatment of COVID-19 patients. Thermal screening at Airports, Seaports, Railway Stations and Bus Terminals is the first and foremost step to identify persons carrying virus. Proper arrangements for compulsory quarantine for 14 days of suspects with infection.

 

Investigations should be done as per WHO guidelines for pandemic surveillance. Containment Zones with large number of COVID-19 patients should be put under strict surveillance to avoid community spread of the disease. Strict enforcement of health & hygiene-related discipline could save the citizens and the nation.

Carcinomas & Role of Diagnostic Pathology

The word carcinoma is synonym for cancer or malignancy in medical science. Carcinomas may develop from a variety of epithelial tissues of various sites of human body. Epithelial tissues (layers of body cells lining the wall) of respiratory tract, gastrointestinal tract (GI tract) reproductive tract (vagina, cervix, uterus and fallopian tubes), oral cavity, head & neck, breast and skin may transform as carcinoma due to viral infections, genetic mutations and/or biochemical changes in our body. The histopathological diagnosis based on varied morphology of cells and their nuclei is very challenging for the pathologists. For the accurate differential diagnosis of carcinomas found in the primary organs and at metastatic sites in the biopsy materials/specimens, pathologists have to depend on advanced techniques/methodologies like immonohistochemistry (IHC), in-situ hybridization, molecular genetics, microarray etc.


A variety of panels of tumor specific & cells’ phenotype specific primary antibodies have been chalked-out through worldwide deliberations for accurate diagnosis of carcinomas/malignancies with reference to established literature and WHO classifications of carcinomas/malignancies. An accurate diagnosis provides the direction for the line of treatment or surgical interventions. However, individual results of advanced investigations may vary somewhat within diagnostic centers, probably due to protocols followed. The storage conditions and exhausted lifespan of primary antibodies used for IHC may influence the outcome of final result, so there is need for strict quality assurance at pathological diagnostic centers.

Rabies: Signs and Symptoms in Animals and Human Beings

Rabies is a disease, which man acquires from vertebrate animals. The disease is caused by a virus infecting the nervous tissue. Rabies causes 100% mortality if the human beings bitten by rabid animal and are not adequately vaccinated. Rabies is a disease of antiquity, having been known to mankind probably earlier than 2000 BC. Clinically, in both animals and man, rabies can manifest either in the form of hyperactivity (furious rabies) or paralysis (paralytic or dumb rabies). Human beings if not given prophylactic vaccination after animal bite always develop furious type rabies, whereas around 25% of dogs develop furious type rabies. Excessive salivation and lacrimation may also be present in affected animals and human beings. Hydrophobia (fear from water) may also be present in majority of the cases. No drugs work after the development of symptoms of rabies and patients lapse into coma and die. Millions of people are treated worldwide with post bite prophylactic vaccination for suspected rabid dog bites, every year.

The great Louis Pasteur was the first authority to make rabies vaccine by inactivating rabies virus obtained from the spinal cord of infected rabbit. The 'old stock vaccine' is made from the monkey's nervous tissue and 12 to 14 injections of this vaccine are required for 100% protection. Almost half of people vaccinated with 'old stock vaccine' may have appreciable local side effects and only 5 in 10,000 may have serious side effects. The latest anti-rabies vaccines have minimal side effects. The Purified Chick Embryo Cell (PCEC) and Human Diploid Cell (HDC) vaccines give 100% protection not only to those who are bitten by rabid dogs but also to those who work with rabies virus and handle reservoir animals. All vaccines are easily available worldwide at reasonable rates. Neurological complications may develop in persons vaccinated with 'old stock vaccine'.

Incubation Period: The incubation period of rabies disease is usually between one and two months. In extreme cases incubation period may be a few days or rarely, even years. The site of the bite is indicative in determining the length of incubation period. Infants and children have a shorter incubation period than adults. Restlessness, agitation, excitation, confusion, muscle spasms, hallucinations, thought disorders and hydrophobia are common signs of possibility of development of rabies in person infected with rabies virus.

Diagnosis: The diagnosis of rabies in animals is made by microscopic examination of stained brain smears or histological sections for Negri bodies. The biological test for rabies is intra-cerebral inoculation of mice with the nervous tissue squash of animals or body secretions of infected human beings and isolation of virus from inoculated mice after an incubation period of 1-2 weeks. In human beings the rabies virus can directly be isolated from saliva, urine and cerebrospinal fluid, and revealed by electron microscopic study.