Viral Pneumonia: The presentation of mild central vascular congestion, interstitial opacities, and peribronchial thickening on the chest X-ray is highly suggestive of a viral infectious process. The symptoms and radiographic findings are consistent with viral pneumonia, which is a common cause of such presentations in adults.

Pulmonary Edema: Given the presence of mild central vascular congestion, pulmonary edema should be considered, especially if there are underlying conditions such as heart failure or if the patient has been exposed to high altitudes. However, the absence of more significant vascular redistribution or cardiomegaly might make this less likely.
Atypical Bacterial Pneumonia: Atypical bacteria like Mycoplasma pneumoniae can cause similar radiographic findings and should be considered, especially in a young adult presenting with respiratory symptoms.
Influenza: Depending on the season and the patient's vaccination status, influenza could be a likely diagnosis, presenting with similar radiographic findings and clinical symptoms.

Pulmonary Embolism: Although less likely given the radiographic findings, pulmonary embolism can sometimes present with non-specific interstitial changes and should always be considered, especially if there are risk factors for thromboembolism, due to its high mortality if missed.
Acute Respiratory Distress Syndrome (ARDS): Early stages of ARDS can present with similar findings, and it's crucial to identify and manage promptly due to its high morbidity and mortality.
Cardiogenic Shock: If the patient has underlying cardiac disease, cardiogenic shock leading to pulmonary edema could be a life-threatening condition that needs immediate attention.

Interstitial Lung Disease (ILD): Certain types of ILD could present with interstitial opacities, but this would be less likely given the acute presentation and would typically require further diagnostic workup.
Lymphangitic Carcinomatosis: A rare condition where metastatic cancer spreads to the lymphatics of the lung, presenting with interstitial opacities, but this would be unusual without a known history of cancer.
Eosinophilic Pneumonia: A rare condition that can present with interstitial infiltrates, often associated with eosinophilia, and would require specific diagnostic testing for confirmation.