cold, common, acute viral infection of the mucous membranes of the nose and throat, often involving the sinuses. The typical sore throat, sneezing, and fatigue may be accompanied by body aches, headache, low fever, and chills. The congested and discharging mucous membrane may become a fertile ground for a secondary bacterial invasion that can spread to the larynx, bronchi, lungs, or ears. Uncomplicated infections usually last from three to ten days.

The cold is the most common human ailment. Most adult Americans suffer from one to four colds per year, but children ages one to five—who are the most susceptible—typically may contract as many as eight. Colds are spread by respiratory droplets or by contaminated hands or objects. Although the incidence of colds is higher in winter, exposure to chilling or dampness is considered to be of little significance.

Any one of up to 200 viruses (such as the rhinoviruses, coronaviruses, or respiratory syncytial virus [RSV]) can cause colds, to which it seems almost no one is immune. Infection with a viral strain confers only temporary immunity to that strain. Colds in infants and young children caused by RSV can progress to pneumonia and other complications, especially in those under a year old who were born prematurely or have chronic lung disease; RSV causes an estimated 4,500 deaths yearly in these groups in the United States.

There is no treatment for the common cold other than that aimed at relieving symptoms and keeping the body well-rested, -fed, and -hydrated. Because of the growing problem of drug resistance, doctors are being discouraged from prescribing antibiotics (which do not affect viruses) for colds unless secondary bacterial infection makes them necessary. There is no convincing evidence that vitamin C megadoses can prevent the common cold.

Researchers have reported reduction or prevention of cold symptoms in human tests of an experimental drug against rhinoviruses, which cause nearly half of all colds. The drug acts by imitating a molecule in the body called ICAM-1, to which the rhinovirus attaches to produce colds. As rhinoviruses attach to the decoy molecules instead, the likelihood or severity of infection is decreased.

cold war, term used to describe the shifting struggle for power and prestige between the Western powers and the Communist bloc from the end of World War II until 1989. Of worldwide proportions, the conflict was tacit in the ideological differences between communism and capitalist democracy.

The Iron Curtain and Containment

Mutual suspicion had long existed between the West and the USSR, and friction was sometimes manifest in the Grand Alliance during World War II. After the war the West felt threatened by the continued expansionist policy of the Soviet Union, and the traditional Russian fear of incursion from the West continued. Communists seized power in Eastern Europe with the support of the Red Army, the Russian occupation zones in Germany and Austria were sealed off by army patrols, and threats were directed against Turkey and Greece. Conflict sometimes grew intense in the United Nations, which was at times incapacitated by the ramifications of the cold war, at others effective in dealing with immediate issues.

In a famous speech (1946) at Fulton, Mo., Sir Winston Churchill warned of an implacable threat that lay behind a Communist "iron curtain." The United States, taking the lead against the expansion of Soviet influence, rallied the West with the Truman Doctrine, under which immediate aid was given to Turkey and Greece. Also fearing the rise of Communism in war-torn Western Europe, the United States inaugurated the European Recovery Program, known as the Marshall Plan, which helped to restore prosperity and influenced the subsequent growth of what has become the European Union.

During the cold war the general policy of the West toward the Communist states was to contain them (i.e., keep them within their current borders) with the hope that internal division, failure, or evolution might end their threat. In 1948 the Soviet Union directly challenged the West by instituting a blockade of the western sectors of Berlin, but the United States airlifted supplies into the city until the blockade was withdrawn (see Berlin airlift). The challenges in Europe influenced the United States to reverse its traditional policy of avoiding permanent alliances; in 1949 the United States and 11 other nations signed the North Atlantic Treaty (NATO; see North Atlantic Treaty Organization). The Communist bloc subsequently formed (1955) the Warsaw Treaty Organization as a counterbalance to NATO.

The Cold War Worldwide

In Asia, the Communist cause gained great impetus when the Communists under Mao Zedong gained control of mainland China in 1949. The United States continued to support Nationalist China, with its headquarters on Taiwan. President Truman, fearing the appeal of Communism to the peoples of Asia, Africa, and Latin America, created the Point Four program, which was intended to help underdeveloped areas. Strife continued, however, and in 1950 Communist forces from North Korea attacked South Korea, precipitating the Korean War. Chinese Communist troops entered the conflict in large numbers, but were checked by UN forces, especially those of the United States. The focus of the cold war in Asia soon shifted to the southeast. China supported insurgent guerrillas in Vietnam, Laos, and Cambodia; the United States, on the other side, played a leading role in the formation of the Southeast Asia Treaty Organization and provided large-scale military aid, but guerrilla warfare continued.

The newly emerging nations of Asia and Africa soon became the scene of cold-war skirmishes, and the United States and the Soviet Union (and later China) competed for their allegiance, often through economic aid; however, many of these nations succeeded in remaining neutral. As the cold-war struggle continued in Southeast Asia, in the Middle East, in Africa (in nations such as Congo (Kinshasa), Angola, and others), and in Latin America (where the United States supported the Alliance for Progress to counter leftist appeal), both the Soviet Union and the United States supported and maintained sometimes brutal regimes (through military, financial, and other forms of aid) in return for their allegiance.

In Europe, the East German government erected the Berlin Wall in late 1961 to check the embarrassing flow of East Germans to the West. In 1962 a tense confrontation occurred between the United States and the Soviet Union after U.S. intelligence discovered the presence of Soviet missile installations in Cuba. Direct conflict was avoided, however, when Premier Khrushchev ordered ships carrying rockets to Cuba to turn around rather than meet U.S. vessels sent to intercept them (see Cuban Missile Crisis). It was obvious from this and other confrontations that neither major power wanted to risk nuclear war.

Hopes for rapprochement between the Soviet Union and the West had been raised by a relaxation in Soviet policy after the death (1953) of Joseph Stalin. Conferences held in that period seemed more amiable, and hopes were high for a permanent ban on nuclear weapons. However, the success of the Soviet artificial satellite Sputnik in 1957, attesting to Soviet technological know-how, introduced new international competition in space exploration and missile capability. Moreover, both Soviet Premier Nikita Khrushchev and U.S. Secretary of State John Foster Dulles grimly threatened "massive retaliation" for any aggression, and the Soviet Union's resumption (1961) of nuclear tests temporarily dashed disarmament hopes. While Khrushchev spoke of peaceful victory, extremists in both camps agitated for a more warlike course, even at the risk of nuclear catastrophe. China began to accuse the USSR of conciliatory policies toward the West, and by the early 1960s ideological differences between the two countries had become increasingly evident.

Detente and the End of the Cold War

During the late 1950s and early 60s both European alliance systems began to weaken somewhat; in the Western bloc, France began to explore closer relations with Eastern Europe and the possibility of withdrawing its forces from NATO. In the Soviet bloc, Romania took the lead in departing from Soviet policy. U.S. involvement in the Vietnam War in Southeast Asia led to additional conflict with some of its European allies and diverted its attention from the cold war in Europe. All these factors combined to loosen the rigid pattern of international relationships and resulted in a period of detente.

In the 1980s, U.S. President Ronald Reagan revived cold-war policies and rhetoric, referring to the Soviet Union as the "evil empire" and escalating the nuclear arms race; some have argued this stance was responsible for the eventual collapse of Soviet Communism while others attribute it to the inherent weakness of the Soviet state. From 1989 to 1991 the cold war came to an end with the opening of the Berlin Wall, the collapse of Communist party dictatorship in Eastern Europe, the reunification of Germany, and the disintegration of the Soviet Union.

cold storage: see refrigeration.

cold sore: see herpes simplex.

cold fusion or low-temperature fusion, nuclear fusion of deuterium, an isotope of hydrogen, at or relatively near room temperature. Fusion, the reaction involved in the release of the destructive energy of a hydrogen bomb, requires extremely high temperatures, and investigations of fusion as a possible energy source have focused on the problems involved in designing an apparatus to contain and sustain such a reaction (see nuclear energy; nuclear reactor). In 1989 B. Stanley Pons and Martin Fleischmann, chemists at the Univ. of Utah, announced that an experiment conducted at room temperature using platinum and palladium electrodes immersed in heavy water (deuterium oxide) had produced excess heat and other byproducts that they ascribed to a fusion reaction. Attempts to replicate their experiment produced initially conflicting results, but several early announcements of experimental confirmation were later retracted. Pons and Fleischmann were also later criticized for having skewed data to show the emission of gamma rays at an energy level typical of fusion.

Research into the possibility of cold fusion, by Fleischmann and others, nonetheless continues, because of intriguing but inconclusive experimental results—such as claims of the production of excess heat, helium, or tritium where heavy water reacts with metals—and because of the desirability of producing relatively nonpolluting fusion energy in quantity at any temperature. Cold-fusion proponents believe that the fusion mechanism is different from that of "hot fusion" in that it encompasses some type of unusual nuclear reaction in the metal lattice involving deuterium and possibly other atoms. Several dozen models to explain the observed phenomena have been advanced, but none accounts for the full range of experimental observations.

cold frame, in horticulture, sun-heated board frame covered with a removable top of glass or other transparent material and sunk into the ground. The top may be solid or slatted or screened for shade. The cold frame is used to start seedlings in early spring (four to six weeks before the average frost-free date), to harden seedlings or plants removed from greenhouses or hotbeds, and to protect plants during the winter. A hotbed is an artificially heated cold frame.

Viral infection of the upper and sometimes the lower respiratory tract. Symptoms, which are relatively mild, include sneezing, fatigue, sore throat, and stuffy or runny nose (but not fever); they usually last only a few days. About 200 different strains of virus can produce colds; they are spread by direct or indirect contact. The cold is the most common of all illnesses; the average person gets several every year. Incidence peaks in the fall. Treatment involves rest, adequate fluid intake, and over-the-counter remedies for the symptoms. Antibiotics do not combat the virus but may be given if secondary infections develop.

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Any so-called cold-blooded animal; that is, any animal whose regulation of body temperature depends on external sources, such as sunlight or a heated rock surface. The ectotherms include the fishes, amphibians, reptiles, and invertebrates. The body temperatures of aquatic ectotherms are usually very close to those of the water. Ectotherms do not require as much food as warm-blooded animals (endotherms) of the same size, but most cannot deal as well with cold surroundings.

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