Coronaviruses and rotaviruses are common causes of respiratory and gastrointestinal infections in humans. Coronaviruses are enveloped viruses that cause common colds and gastroenteritis, while rotaviruses are double-shelled viruses that appear wheel-shaped under microscopy and are a major cause of diarrhea in infants and children worldwide. Laboratory diagnosis of these infections can be done through electron microscopy of feces to detect viral morphology, serological testing of paired patient sera to detect rising antibody titers, and virus isolation, though this last method is not widely used for coronaviruses. Treatment is supportive for coronavirus infections as no antiviral drugs or vaccines exist, while rehydration therapy and rotavirus vaccines are

1. THEME: CORONAVIRUSES AND ROTAVIRUSES. GENERAL PROPERTIES.
LABORATORY DIAGNOSTICS OF HUMAN DISEASES CAUSED BY THEM.
I. THEORETICAL QUESTIONS
1. General characteristic and classification of the Coronaviruses.
2. Morphology, antigen structure and resistance of human coronaviruses. Methods of their
cultivation, indication and identification.
3. Infections caused by coronaviruses (respiratory tract infection and infant diarrhea) :
epidemiology, pathogenesis and immunity.
4. Laboratory diagnostics of the coronavirus infections
a. Rapid diagnostics (microscopy);
b. Serological method
5. General characteristic and classification of the Rotaviruses.
6. Morphology, antigen structure and resistance of human rotaviruses. Methods of their
cultivation, indication and identification.
7. Infections caused by rotaviruses (diarrhea of children and adult) : epidemiology,
pathogenesis and immunity.
8. Laboratory diagnostics of the rotavirus infections
a. Rapid diagnostics (microscopy and detection of the virus antigen in the feces);
b. Serological method
c. Experimental infection
9. Prevention and therapy of human rotavirus infections.
CORONAVIRUSES
Morphology: A group of spherical or pleomorphic enveloped RN A viruses, carrying petal or club
shaped peplomers on their surface has been classified as coronaviruses. The name refers to the fringe
of surface projections surrounding the virus resembling the solar corona. They have positive single-
stranded RNA with an enveloped helical nucleocapsid.
Antigen strucuture: they have inner group specific nucleocapsid antigen and surface typespecific
antigens. Many serotypes of human coronaviruses have been recognised.
Pathogenecity. The group originally contained veterinary pathogens such as avian infection
bronchitis virus, mouse hepatitis virus and transmissible gastroenteritis virus of swine. Human
coronaviruses cause common cold-like illness similar to rhinoviruses. In infants they also can cause
gastroenteritis and necrotizing enterocolitis. Inoculation in human volunteers induces common cold
after an incubation period of 2-5 days.
Immunity: The resulting immunity is poor and reinfections can occur even with the same serotype.
Isolation and cultivation. Human coronaviruses were first isolated from cases of common cold by
inoculating organ cultures of human embryonic trachea with nasopharyngeal washings. Inhibition of
ciliary motility indicates virus growth (indication). Though many strains grow only on organ
cultures, some grow on monolayers of diploid human embryonic fibroblasts, with minimal
cytopathic effects.
Laboratory diagnostics. Two methods are used to diagnose coronavirus infection.
1. To diagnose gastroenteritis electron microscopy of feces is
used. Typical morphology of virus with solar corona is enough to make presumptive diagnose.
Immune electron microscopy is another method of microscopic examination.
2. Serology. Paired sera is investigated with CFT. Four-fold
rising of antibody titer confirms diagnose of coronavirus infection.
3. Virus isolation is not widely used
Therapy and prophylaxis: there no antiviral drugs to treat coronavirus infections. The treatment is
symptomatically. There are no vaccines to prevent coronavirus gastroenteritis.

2. ROTAVIRUS
Rotaviruses belong to family Reoviridae and genus Rotavirus. Members of this family are double
shelled icosahedral viruses with double-stranded segmented RNA genome. They are non-
enveloped and resistant to lipid solvents.
Morphology. These double walled viruses present a characteristic appearance under the electron
microscope, resembling little wheels with short spokes radiating from a wide hub to a clearly
defined outer rim. The name is derived from rota, in Latin, meaning wheel. Both 'complete' and
'incomplete' particles are seen. The complete or 'double shelled' virus measures about 65-70 nm in
diameter and has a smooth surface. The incomplete or 'single shelled" virus is smaller, about 60
nm, with a rough surface and is rotavirus that has lost the outer shell. 'Empty' particles without the
RNA core are also seen.
Antigen structure. Rotaviruses share a common group antigen situated in the inner capsid layer.
Rotaviruses have been classified into at least seven antigenic groups (A to G). Group A strains,
which cause the majority of human infections have been classified into subgroups (I and II) by
ELISA, CF or immune adherence agglutination, and into many serotypes (1, 2, 3 etc) by
neutralisation tests ADRV strains belong to group B. By polyacrylamide gel electrophoresis,
rotavirus strains can be classified into several electrophoretypes, based on the patterns of
migration of the viral RNA.
Pathogenecity. Rotaviruses are a class of viruses causing diarrhea in the young of many
animals and some birds. The human rotavirus is related to the viruses of epidemic diarrhea of
infant mice (EDIM), Nebraska calf diarrhea and the simian virus SA11. Rotaviruses are the
commonest cause of diarrhea in infants and children the world over and account for about half the
cases of children hospitalised for diarrhea. It occurs throughout the year but predominates in
winter months, when the virus may be detected in most of the patients. It sometimes produces
large epidemics of diarrhea in winter. Rotavirus diarrhea is usually seen in children below the age
of five years, but is most frequent between 6 and 24 months of age. Infection is not infrequent in
neonates but they seldom develop diarrhea, perhaps because of maternal passive immunitiy. By the
age of five years, most children have had clinical or subclinical infection, so rotavirus diarrhea is
very uncommon in older children and adults.
Isolation and cultivation. Human rotavirus does not grow readily in cell cultures but some strains
have been adapted for serial growth in tissue cultures. Rotavirus growth is facilitated by trypsin
treatment and rolling of tissue cultures. As calf and simian viruses grow readily in cell cultures,
they have been used as antigens for serological studies.
Rotavirus infection (clinical findings, therapy and prophylaxis). Infection is by the fecal-oral
route. The incubation period is 2-3 days. Vomiting and diarrhea occur with little or no fever.
Stools are usually greenish yellow or pale, with no blood or mucus. The disease is self-limited and
recovery occurs within 5-10 days. Mortality is low. Rehydration is all the treatment needed.
Prophylaxis. Rotavirus vaccines have been developed. An oral rotavirus vaccine given in three
doses, at 2, 4 and 6 months of age has been approved in the USA and the European Union.
Laboratory diagnostics:
1. Microscopy. The methods originally used for diagnosis
were electron microscopy and immunoelectron microscopy. These are expensive and
complicated procedures.
2. Serological techniques for demonstration of the virus in
stools are simpler and as sensitive. CF, CIE, ELISA and passive agglutination have beer used for
this purpose.
3. Serology. Patient sera are used to diagnose infection. IgM
and IgG antibodies can be demonstrated in the blood of infected children.
4. Biological method (experimental infection). All
rotaviruses share common antigens. Though the viruses are in general species-specific,
interspecies infection can be induced experimentally. Human rotavirus infection has been
transferred to piglets, calves and monkeys. It is not known whether human infection can be caused
by animal rotaviruses.
II. Students Practical activities:

3. 1. Estimate the complement-fixing antibody titer with rotavirus and coronavirus
diagnosticums in paired patient’s sera with presumptive diagnosis “virus diarrhea”.
Determine the rising of antibody titer to different viruses and make a conclusion.
2. Write down the scheme of laboratory diagnosis of coronavirus and rotavirus infections.