Influenza has hit the Washington metropolitan area with such force that the emergency room staff at the Children's Hospital National Medical Center has been overwhelmed and has called for volunteer help from other hospital staffers.

At the Washington Hospital Center, officials yesterday announced that they are limiting visits to patients to members of the patients' immediate families because "of the high incidence of flu-like illness in the community."

Throughout the Washington area hospitals are reporting sharp increases in emergency room visits. The federal Center for Disease Control, in Atlanta, yesterday reported influenza cases in 31 states in addition to the District of Columbia, Maryland and Virginia.

As in most areas, the virus isolated here thus far as been the A-Texas variety, which is similar to the A-Victoria seen in the past several flu seasons.

According to specialists in viral diseases, those persons vaccinated against A-Victoria flu, or those persons who contracted that flu, have some resistance to the A-Texas because of the closeness of the two strains. While they can still contact the A-Texas, these experts say, they are much more likely to have milder cases of it than someone with no immunities at all.

There is still no sign in this country of the new flu first reported this year in the Soviet Union and Hong Kong, A-USSR-77.

That flu, which reportedly infected 35 million Russians, has now been reported in Finland and Taiwan, and is expected to reach this country late this winter or during next year's flu season.

The A-Texas strain that is infecting Washingtonians is a "typical" flu, lasting from three days to a week. It is generally experienced in the form of high fever, body aches, headache, cough and, in some cases, abdominal pain.

As is the case with any influenza, the only treatment is plenty of fluids, bed rest and a fever reducer, such as aspirin, for the fever and aches and pains.

This flu, like most others, is only life threatening to the very old, very young and those already suffering from respiratory or cardiovascular disease. Some hospitals have already reported a few cases with complications, such as pneumonia, but those cases have been rare, and there have not been any deaths reported.

Dr. Kenneth Philbrook, who works in the emergency room at Suburban Hospital, called the outbreak a "near epidemic. It's a four-fold increase of what we usually see. We normally see two to four flu-type symptoms a day. Now we're seeing 15 to 18."

Outbreaks have also been reported by Fairfax Hospital, which has seen a moderate increase in cases, and Greater Southeast Community Hospital, which reports that its emergency room visits have risen from an average of about 200 a day to about 250, and most of the increase has been attributed to the flu.

At George Washington University Hospital, which experienced very little flu-like illness earlier in the season, a spokeswoman said yesterday, "We're seeing the beginning of an epidemic."

According to the CDC, the worst outbreaks thus far have occurred in New York, New Jersey, Tennessee, Illinois, Pennsylvania and Wisconsin.

Epidemiologists from all over the world are expected to meet Monday in Geneva, at a World Health Organization-sponsored conference on the Russian flu.

American pharmaceutical manufacturers have already begun the race to produce a vaccine against the strain before it appears in this country. Epidemiologists in this country are expected to meet, probably at the National Institutes of Health, sometime within the next two weeks, to discuss possible strategies for fighting the flu here.

The CDC is already using the quarantine stations at major international airports in this country - like Dulles International here and John F. Kennedy, in New York - to check incoming travelers for the Russian flu.

Anyone coming in from a country in which the flu has been reported is being asked if they have any flu-like symptoms. If they have, their throats are being cultured. In this manner the CDC hopes to at least know when and how the virus enters the country.

American public health officials are reacting to the threat of the Russian flu because of the bad experience with the swine flu immunization program last year.

Many of the experts attending a Dec. 22 meeting at CDC headquarters in Atlanta cautioned against rushing into a mass immunization program, as was done in 1976 and last year when the threat never materialized.

The CDC now has a stock pile of $43 million worth of vaccine against the swine flu, which failed to materialize last year and has shown no signs of appearing this season. That vaccine has thus far proven ineffective against the Soviet flu.