Page 52 - rp-may-2020

CPD ACTIVITY 50
RET AIL PHARMA C Y • MA Y 2020
FROM PAGE 49
respiratory tract. The challenge to define the syndromes
exactly is related to the great variation in severity, duration
and the type of symptoms. Table 1 outlines the commonly
involved virus groups and the mechanisms that generate
URTI symptoms, while Table 2 outlines pathognomonic
features (characteristics of specific disease) involved
in cold and flu.
Considering other viral conditions: emerging
viral diseases
Viruses (especially RNA viruses) have profound capacity
to modulate or evade the natural reservoir (host), resulting
in persistence causing outbreaks and pandemics in humans.
It should be noted that the emergence of zoonotic disease
(infrequently spread from animals to humans) is multifactorial.
It may involve, among other things, human behaviour such
as travel, trading practices, farming activities including vector
distribution, and the genetics of the microbe.
Interspecies transmission of zoonotic agents from their natural
reservoir is still an unusual event, and for most, zoonoses and
human-to-human transmission are rare. However, increased
spillover events increase the chances of the emergence of an
adapted virus that is highly transmissible, as in the case of the
coronavirus pandemic of 2019/20. Table 3 outlines the new,
re-emerging, or drug resistant viral infections whose incidence
in humans has increased within the past two decades, or
whose incidence threatens to increase in the near future.
Efficacy and safety of OTC treatments for
common cold and flu
Common cold and flu for the purpose of this review are
deemed to cover all URTIs. Antihistamines, decongestants
and anticholinergics are widely used as non-prescription (OTC)
medicines to treat symptoms of cold and flu.46
Table 1.
Viral causes of the common cold.
Virus groups
Comment on the mechanisms generating
URTI symptoms
Rhinovirus
Infection occurs predominantly during the
winter months.6
Human rhinoviruses (HRV) are the major cause
of common cold and frequently associated with
exacerbation of asthma, otitis media, sinusitis
and pneumonia.7
After HRV attachment to human receptors on
respiratory epithelial cells, the viral genome is
released from the endosome into the cytoplasm,
where viral replication occurs, and virus is released
upon cell lysis.8,9
Influenza virus
Infection predominates during winter months. Influenza
viruses are significant human respiratory pathogens
that cause both seasonal and endemic infections,
including periodic, unpredictable pandemics.10
Uncomplicated human influenza virus infection
causes transient tracheo-bronchitis, corresponding
with predominant virus attachment to tracheal and
bronchial epithelial cells. None of the symptoms are
pathognomonic for any specific virus, as virtually
all known HRVs can cause any combination of
these symptoms.11
Coronavirus
Long considered inconsequential pathogens, causing
the ‘common cold’ in otherwise healthy people, in
recent years, three highly pathogenic human corona
viruses (HCoVs) – severe acute respiratory syndrome
coronavirus (SARS-CoV) and Middle East respiratory
syndrome coronavirus (MERS-CoV) – have emerged
from animal reservoirs causing pandemics with
significant morbidity and mortality, including the high-
profile HCoV pandemic of 2019/20, (SARS-CoV2).
5
Respiratory syncytial Infection predominates during winter months.
virus
Associated with a range of respiratory illnesses,
from common cold-like symptoms to serious lower
respiratory tract illnesses such as pneumonia
and bronchiolitis.12
Recognised as a significant problem in the elderly,
persons with cardiopulmonary diseases, and
immunocompromised hosts.13
Parainfluenza virus
Infection predominates during winter months. Human
parainfluenza (HPIV) is genetically and antigenically
divided into four types, 1 to 4. Further major subtypes
of HPIV-4 (A and B) have been identified.
Each subtype can cause somewhat unique clinical
diseases in different hosts. This virus causes 50 to
74.2 per cent of croup cases.14
Adenovirus
Adenovirus is typically transmitted from person to
person via respiratory droplets, and less commonly
via the conjunctival and faecal-oral route. Adenovirus
infection is common, accounting for about five to
15 per cent of URTIs.15, 16
Metapneumovirus
Studies indicate that human metapneumovirus is
prevalent and infects almost all children by age five
years, causing respiratory infections ranging from
uncomplicated URTIs to severe lower respiratory tract
infections in all age groups.17-19
Table 2.
Pathognomonic features of common cold and flu.
Feature
Common cold
Flu
Aetiology
More than seven
different types of
virus groups produce
>200 serologically
different types of
viral aetiologies.
Rhinovirus group
is considered the
most frequent,
followed by influenza
and respiratory
syncytial virus.20
Four strains of influenza
viruses are recognised,
influenza A, B, C and D. (Both
A and B are responsible
for seasonal epidemics
accounting for global
morbidity and mortality.)
Human influenza A virus
infections for which the
pathology is described include
H1N1, H2N2 and H3N2.
Each time a new subtype
enters the human population
it replaces the previously
circulating subtype.10, 21
Seasonality
Year around, peaks
during winter months.
In the temperate regions of
the southern hemisphere,
influenza activity
typically occurs during
April-September.
Site of infection
Upper respiratory tract.
Entire respiratory system.
Symptom onset
Gradual: 1 to 3 days. 22
Sudden: within a few hours.18
Fever, chills
Occasional; low grade
(<37.8C).
Usually present in up to
80 per cent of all flu cases.
A temperature of 37.8C
or higher for three to four
days is typical.23
Headache
Frequent; usually mild.
Characteristic; more severe.22
General aches,
pains
Uncharacteristic.
Characteristic; often severe
and generalised.
Cough, chest
congestion
Mild to moderate; with
hacking cough.
Common; may become
severe.
Sore throat
Common, usually mild.
Sometimes present.
Runny, stuffy nose
Very common;
accompanied by bouts
of sneezing
Sometimes present.
Fatigue, weakness
Mild, if any.
Usual, may be severe and last
two to three weeks.
Extreme
exhaustion
Uncharacteristic.
Frequent.