No abstract

Lentogenic Newcastle disease virus (lNDV) such as Lasota strain and low pathogenicity avian influenza such as H9N2 virus are two of the most economically important viruses affecting poultry worldwide, and little attention in recent years has been paid to simultaneous infections in chickens with these two viruses for the reason that co-infection do occur but are not easily detected. In the present study, chickens were inoculated with lNDV (Lasota) and LPAIV (A/chicken/Tehran/ZMT-173/99(H9N2)) simultaneously or sequentially three days apart. Oropharyngeal and cloacal swabs were collected from chickens from 1 to 14 days after inoculation. RRT-PCR for AIV and NDV detection was performed. The rate of viral shedding was measured within 14 days. No clinical symptoms were observed during the experiment however the pattern of virus shed was different with co-infection, thus comparing the results obtained from viral shedding showed that AIV is a much stronger agent than NDV in the occurrence of viral interference. This is due to the fact that in simultaneous inoculation, AIV replication delayed and reduced NDV replication, while replication of Lasota in simultaneous or pre-inoculated inoculation could not significantly disrupt H9N2 virus replication. These findings indicate that the infection with one virus can interfere with the replication of another, modifying the pathogenesis of the viruses. So, infection of the host with both viral agents simultaneously causes higher shedding of LPAIV than lNDV in OP and CL areas. In conclusion, coinfection with LPAVI in chickens did not impact clinical signs but affected the replication dynamics of these viruses.

The novel human coronavirus, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), which results in the coronavirus disease 2019 (COVID-19), has caused a serious threat to global public health. Therefore, many studies are performed on the causes and prevalence of this disease and the possible co-occurrence of the infection with other viral and bacterial pathogens is investigated. Respiratory infections predispose patients to co‐infections and these lead to increased disease severity and mortality. Numerous types of antibiotics have been employed for the prevention and treatment of bacterial co‐infection and secondary bacterial infections in patients with a SARS-CoV-2 infection. Although antibiotics do not directly affect SARS‐CoV‐2, viral respiratory infections often result in bacterial pneumonia. It is possible that some patients die from bacterial co‐infection rather than virus itself. Therefore, bacterial co‐infection and secondary bacterial infection are considered critical risk factors for the severity and mortality rates of COVID‐19. In this review, we will summarize the bacterial co‐infection and secondary bacterial infection in some featured respiratory viral infections, especially COVID‐19.