Bees are insects closely associated with flowers, although their lives are more varied than the familiar image of a large colony in a hive. Many species live alone or in small associations rather than in the social organisation seen in honey bees. Their size, appearance, nesting behaviour, and preferred plants differ. This variety is important when considering how bees use gardens, grasslands, woodlands, and other environments. Flowers provide pollen and nectar that many bees collect or consume. During visits, pollen can move between flowers and contribute to pollination. The details of this relationship depend on the structure of the flower and the behaviour of the bee. Some visits transfer more pollen than others. It is therefore useful to consider what the insect actually does on a flower rather than assuming that every brief landing has the same effect. The requirements for nesting vary among species. Some use holes in the ground, while others occupy cavities or make use of suitable plant material. A nest may be difficult to notice even in a place where adult bees are frequently seen. Food plants and nesting spaces are separate resources, and both can influence which kinds of bees use an area. A tidy-looking surface is not always the most informative guide to what is present. Social bees show forms of cooperation that can include shared nesting, food collection, and care of young. Solitary species arrange these activities differently. Comparing these ways of life prevents one well-known example from standing in for the whole group. It also helps explain why changes to a landscape can affect different bee species in different ways, even when they visit some of the same flowers. Observation can focus on the timing of visits, the kinds of flowers used, and the movement between feeding and nesting areas. A small patch of flowers may attract several insects that look similar at first glance. Differences in shape and behaviour become clearer with repeated, undisturbed watching. Bees illustrate how the details of individual species contribute to a wider network of relationships between plants and the animals that visit them.

Coronavirus disease 2019

COVID-19 is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic.

The symptoms of COVID‑19 can vary but often include fever,[7] fatigue, cough, breathing difficulties, loss of smell, and loss of taste.[8][9][10] Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms.[11][12] Of those who develop symptoms noticeable enough to be classified as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction).[13] Older people have a higher risk of developing severe symptoms. Some complications result in death. Some people continue to experience a range of effects (long COVID) for months or years after infection, and damage to organs has been observed.[14] Multi-year studies on the long-term effects are ongoing.[15]

COVID‑19 transmission occurs when infectious particles are breathed in or come into contact with the eyes, nose, or mouth. The risk is highest when people are in close proximity, but small airborne particles containing the virus can remain suspended in the air and travel over longer distances, particularly indoors. Transmission can also occur when people touch their eyes, nose, or mouth after touching surfaces or objects that have been contaminated by the virus. People remain contagious for up to 20 days and can spread the virus even if they do not develop symptoms.[16]

Testing methods for COVID-19 to detect the virus’s nucleic acid include real-time reverse transcription polymerase chain reaction (RT‑PCR),[17][18] transcription-mediated amplification,[17][18][19] and reverse transcription loop-mediated isothermal amplification (RT‑LAMP)[17][18] from a nasopharyngeal swab.[20]

Several COVID-19 vaccines have been approved and distributed in various countries, many of which have initiated mass vaccination campaigns. Other preventive measures include physical or social distancing, quarantining, ventilation of indoor spaces, use of face masks or coverings in public, covering coughs and sneezes, hand washing, and keeping unwashed hands away from the face. While drugs have been developed to inhibit the virus, the primary treatment is still symptomatic, managing the disease through supportive care, isolation, and experimental measures.