Early viruses

The disease outcome i. Interferences between influenza virus types and subtypes were observed when sequential infections were attempted in an interval ranging from 3 to 7 days Table 2. For this period, the authors suggested that innate immunity and intrinsic antiviral factors mediated by infection of ferrets with the interfering virus may prevent or delay infection and replication of the second virus Surveillance of respiratory viral infections in Norway showed that RSV was less frequently detected during influenza epidemics, suggesting viral interference An epidemiologic interference between influenza and RSV was also reported during different winter seasons in other countries 32 , During the pH1N1 pandemic, the shift in influenza activity was associated with a change in seasonal RSV activity that further supports viral interference 34 — A first infection with RSV reduced the morbidity i.

Infection of ferrets with pH1N1 virus induced a higher production of cytokines, chemokines, and immune mediators in the respiratory tract compared with RSV. RSV and HMPV co-circulate during winter and spring and can be co-detected in nasopharyngeal swab specimens of patients. Nevertheless, the type of interaction between these 2 pneumoviruses is controversial. The inhibition of HMPV replication by RSV was partially prevented in human lung adenocarcinoma A cells deficient for signal transducer and activator of transcription 1, suggesting that viral interference was partially mediated by the host innate immune response.

Many studies reported that the autumn epidemic of HRV might have delayed the circulation of pH1N1 in several countries in Europe 39 — During , a higher rate of HRV infections might have affected the subsequent influenza summer peak and even prevented the influenza epidemic in Hong Kong, China Although mice do not support the complete replication process of HRV, its inoculation 2 days before IAV reduced the severity of influenza disease i.

The protective effect of HRV was associated with an early but controlled pulmonary inflammatory response that enabled rapid clearance of IAV. A negative interaction between RSV and HRV was consistently observed across diverse disease severity patterns, populations, seasons and geographic regions when analyzing 3 cohorts from the United States and the Netherlands Table 2 However, the median duration of symptoms was longer in children who were co-infected that possibly occur outside of temporary immunity window compared with children who had a single RSV infection 14 days vs.

Furthermore, HRV infections were more common in infants given immunoprophylaxis palivizumab against RSV than in infants who did not receive this drug HRV is a nonenveloped virus that is more resistant to hydroalcoholic disinfectant 44 , and its transmission is not prevented by face masks Thus, the differential innate immune responses induced by SARS-CoV-2 and influenza virus in the upper and lower respiratory tracts might influence the type of virus—virus interactions, depending on which virus will infect first.

Lung inflammatory damage and disease severity i. In this study, both viruses were inoculated into hamsters 24 hours apart, which might have been too short a time to induce interference.

In ferrets first infected with influenza virus, there was a lag of 1—2 days before a nonspecific immune response was elicited and during which a co-infection with a second virus was likely to occur Thereafter, the host innate immune response correlates with viral shedding in nasal wash specimens, which peaks at 2—3 days and persists for 5—6 days, corresponding to the window period when viral interference occurs.

Defective viral genomes DVGs are produced during replication of RNA viruses and are believed to play a role in adaptation, viral escape, and persistence DVGs are packaged, forming virus particles that are biochemically and morphologically similar to standard virus. DVGs might hamper the cytopathic effects induced by a wild-type virus. DVGs also rapidly produce cytopathic effects and interfere with replication of other co-infecting homologous or heterologous viruses.

DVGs resulting from influenza virus replication can mediate homologous interference by competing with viral genomes for replication or packaging. The role of DVGs in viral interference is not clearly established, but it is suggested that they could be used as therapeutic interfering particles against respiratory virus infections.

Recent viral infections of the respiratory tract might induce a refractory period during which the host is less likely to be infected by another respiratory virus. This viral interference requires closely spaced virus co-exposures, implying that both viruses share common ecologic conditions e.

Factors that could predict an interference between respiratory viruses include the capacity of the interfering virus to induce a rapid IFN response; the degree of susceptibility of the second virus to immune mediators; the extent to which the different viruses counteract the induction and antiviral effects of IFN; and the differential innate immune response patterns triggered by each viruses in the upper and lower respiratory tracts.

The duration of the refractory period at the host level has not been determined, but might correspond to the period of virus shedding and the associated transient innate immune response. Mathematical models that simulate the co-circulation of seasonal IAV and HRV confirmed that the temporary immunity provided by an IFN response might be sufficient to produce the asynchronous epidemic peaks recorded for these 2 viruses At the population level, the concept of viral interference corresponds to an ecologic phenomenon in which the epidemic caused by one virus delays the start or advances the end of the epidemic caused by another virus.

These episodes are difficult to demonstrate because the transmission dynamics of respiratory viruses might be influenced by social behaviors for different age groups. The contact rate between persons might also vary according to different periods of the year, such as during school opening and closing. Furthermore, a large proportion of respiratory infections are asymptomatic and do not require testing, thus, excluding this part of the population from studies.

Environmental conditions such as temperature and humidity can be confounding factors for viral interference. Prospective epidemiologic studies enabling detection of multiple respiratory viruses in serial nasopharyngeal swab specimens of participants over several epidemic periods would enable demonstration of viral interference.

The type of interaction between respiratory viruses producing distinct epidemic peaks should be then confirmed by evaluating their likelihood of co-detection in patients, as well as the mechanisms involved in ex vivo and in vivo models.

The reappearance of H1N1 virus during and the — pH1N1 pandemic offered the opportunity to study the epidemiologic interactions between the newly circulating virus and seasonal respiratory viruses in northern and southern hemispheres and thus strengthened the concept of viral interference.

During the COVID pandemic, nonpharmacologic interventions have prevented the circulation of most respiratory viruses. Therefore, their potential interactions with SARS-CoV-2 could not be determined in epidemiologic studies, except in some reports at the onset of the pandemic. Once the sanitary restrictions are lifted, the circulation of seasonal respiratory viruses should resume and different types of interactions are expected to occur.

Mathematical modeling predicting the timing and magnitude of epidemics caused by SARS-CoV-2 and seasonal respiratory viruses might improve public health interventions to protect persons at risk for co-infection through introduction of nonpharmacologic measures, adjustment of vaccine schedules, or use of prophylactic agents.

Finally, the interfering and immunostimulatory activities of DVGs make them attractive candidates for development of prophylactic broad-spectrum antiviral drugs or vaccine adjuvant, which would be based on the concept of viral interference Her primary research interests include pathogenesis of infections caused by herpesviruses and Zika virus, emergence of drug resistance, and interactions between respiratory viruses.

Boivin is an infectious disease specialist and the head of the virology laboratory at the Research Center in Infectious Diseases at Laval University. His primary research interests include pathogenesis of infections caused by respiratory viruses, as well as development of vaccines, antiviral drugs, and immunomodulatory agents. Suggested citation for this article: Piret J, Boivin G.

Viral interference between respiratory viruses. Emerg Infect Dis. Table of Contents — Volume 28, Number 2—February Please use the form below to submit correspondence to the authors or contact them at the following address:. Data is collected weekly and does not include downloads and attachments. View data is from. The Altmetric Attention Score for a research output provides an indicator of the amount of attention that it has received. The score is derived from an automated algorithm, and represents a weighted count of the amount of attention Altmetric picked up for a research output.

Section Navigation. Facebook Twitter LinkedIn Syndicate. Table 1 Table 2. Article Metrics. Related Articles. Mumps spread through close-contact activities such as sports, dancing, kissing, etc. From to , the largest outbreak reported 3, cases in a close-knit religious community in New York City after an infected student returned from the UK where there was another outbreak.

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In April of , 20 cases of swine flu were reported in the U. The swine flu was transmitted by pigs as a respiratory disease, usually through contact with farm raisers or participation in fairs. Also known as pertussis, this respiratory disease surmounted to 48, cases in the U.

Coughing fits last up to 10 weeks or more and can be life-threatening for infants. Worldwide, the estimation of whooping cough cases is Middle East Respiratory Syndrome was first found in the Arabian Peninsula in and was also associated with the coronavirus once the illness became viral.

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