Cell-based screening is a common and important technique in antiviral drug research. Viruses need to complete the life cycle of replication in infected cells, which has strict requirements on infected cells. For cell-based screening, the first step is to prepare suitable cell lines that can support viral replication and are as relevant to the disease as possible. The second is the selection of virus strains, as far as possible to select clinical isolates or experimental strains of the virus, although the modified report virus can bring convenience, but there may be ineffective screening inhibitors against clinical isolates of the virus. Depending on the specific virus species, sometimes more than one cell line or virus strain is selected.

Organoids, which are miniature organ analogues from stem cells or progenitor cells with three-dimensional structures, have been able to produce organoids similar to the brain, kidney, lung, intestine, stomach, and liver, with many more in development. Organoids give developers the opportunity to understand how drugs interact with these "mini organs," revolutionizing the field of drug discovery and filling the gap between monotypic cells and complex organisms.

**1. Influenza virus infected mouse model**

Influenza viruses can infect mice and cause respiratory symptoms. Commonly used mouse strains such as BALB/c mice. The way of infection can be through the nasal drip of influenza virus venom, so that the virus enters the respiratory tract and infects mice. After infection, mice will show changes in body temperature, reduced activity, rough hair, and pathological changes in the lungs, such as inflammatory cell infiltration and alveolar damage.

**Second, hepatitis B virus infected mouse model**

1. Transgenic mouse model: Through genetic engineering technology, part or all of the genes of hepatitis B virus are transferred into the mouse genome, so that the mice can continue to express hepatitis B virus protein. This model can be used to study the chronic infection process of hepatitis B virus and to evaluate the efficacy of antiviral drugs.

2. Humanized mouse model: Human liver cells were transplanted into immunodeficient mice and then infected with hepatitis B virus. The model can simulate the human body more realistically

**3. Herpes simplex virus infected mouse model**

Herpes simplex virus infects the skin and nervous system of mice. Herpes simplex venom can be applied to the skin of mice after creating a mild wound. After infection, the skin of mice will appear blisters, ulcers and other symptoms, and in severe cases, the virus can invade the nervous system, causing neurological symptoms.

**4. Mouse models infected with coronavirus**

With the emergence of the novel coronavirus epidemic, mouse models of coronavirus infection have received widespread attention. Certain strains of mice such as BALB/c and C57BL/6 can be infected by certain coronavirus strains. The virus can be inoculated through the nose, and after infection, the mice will show symptoms similar to those of human infection with coronavirus, such as weight loss and lung inflammation.

Bacterial infection of mice usually includes animal systemic infection studies (including drug-resistant bacteria) and animal local infection studies (lung infection, urinary tract infection, leg infection, etc.). Depending on the purpose of the study, there are methods of infection such as nasal drip or intratracheal injection, intraperitoneal or intravenous injection, intragastric injection, and the creation of small wounds on the skin.