Hispanic Americans, soon to be the nation's largest minority, remain largely invisible to the rest of the country, despite severe health problems and an increasing poverty rate, officials reported last week.

"The reason no one talks about us is that no one is counting us," said Jane Delgado, president of the National Coalition of Hispanic Health and Human Service Organizations, often called by the acronym COSSMHO. "Data collection drives national policy in this country, and we don't have good data on Hispanics."

The poverty rate among Hispanic children is about 40 percent, nearly the same as the rate for black children and double the rate for all American children. But general data on Hispanic Americans is sparse. Only 23 of 50 states collect vital statistics on Hispanics as a group. There are no figures, for example, on the national infant mortality rate for Hispanics, Delgado said.

At a conference in Washington, D.C., last week on Latino children in poverty, sponsored by the National Association of Latino Elected and Appointed Officials, more than a dozen experts on Hispanic affairs outlined the problems in medical care, education and employment that are facing the nation's fastest-growing minority.

The Hispanic population of the United States in 1985 reached 17 million, or 7.2 percent of all Americans, and is expected to surpass 25 million by the year 2000. One third of all Hispanic Americans are under age 15.

Hispanics comprise several major ethnic groups: Mexican Americans, concentrated in Southern California and the Southwest; Puerto Ricans, concentrated in New York and New Jersey, and Cuban Americans, concentrated in Florida and New York. Mexican Americans are the largest group, accounting for nearly two thirds of Hispanics.

In the District, there are an estimated 70,000 to 80,000 Hispanics, according to the Office of Latino Affairs. This estimate, based on school enrollments and birth statistics, includes a large number of immigrants from El Salvador and other Central American countries.

But despite their growing numbers, Hispanics have encountered general indifference on the part of most other Americans, said Hernan LaFontaine, superintendent of schools in Hartford, Conn.

"It's more than a benign neglect of the entire Hispanic world surrounding the United States," LaFontaine said. "It's almost as if we never existed."

The 1980s, once touted as "the decade of the Hispanics," have not lived up to that promise, he said. "By and large, I'm disappointed."

One indication of the general lack of concern is that fewer than 1 percent of the grants awarded by private foundations go to projects serving primarily Hispanic groups, said Fernando Torres-Gil, board member of the Council on Foundations.

In 1985, there were 2.5 million Hispanic children below the poverty line, said Thomas Gabe, a legislative analyst at the Congressional Research Service. A family of four is considered poor if its income is below $11,200.

Hispanics make up 10 percent of the nation's children but 20 percent of the poor children, Gabe said.

The disproportionate poverty rate in Hispanic children reflects several factors, said Gabe and panelist Marta Tienda, a sociologist at the University of Wisconsin's Institute for Research on Poverty. These include a high unemployment rate, a tendency toward large families and a high fertility rate among teenagers, many of whom have dropped out of high school.

In families where the mother is under 30 and the father is not present, Gabe said, "nearly 90 percent of the children are poor."

Even among two-parent families, the poverty rate is high for Hispanics, said Robert Greenstein, director of the Center on Budget and Policy Priorities, a nonprofit research organization specializing in analysis of the federal budget.

Seventeen percent of Hispanic two-parent families are below the poverty line, compared with 12 percent of black two-parent families and 6 percent of white two-parent families, Greenstein said.

That reflects the large number of employed Hispanics who "are pushed into poverty by low-paying jobs," Greenstein said. The minimum wage has not been raised since January, 1981, while consumer prices have jumped 30 percent. The income of a person working full time at minimum wage now falls about $2,100 below the official poverty line.

Starting next year, federal health surveys will begin gathering detailed information on Hispanics. Even among states that already collect data, there is little uniformity in the kind of information gathered or the exact definition of Hispanic.

When statisticians try to piece together a national profile of Hispanics' health, Delgado said, "it's like adding up apples and oranges."

The federal government's first report on "Black and Minority Health," issued nearly two years ago, found more complete health and demographic data on Native American Indians and Asian Americans than on Hispanics. The lack of data on Hispanics and other minorities, the report concluded, is one of the major obstacles to an accurate picture of minorities' health and design of programs targeted to their needs.

There's no question that getting medical care is a problem for many Hispanics. They are much more likely than either black or white non-Hispanic Americans to lack a regular source of health care, such as a family doctor or clinic, the Robert Wood Johnson Foundation recently reported in a four-year study of access to health care. Hispanics are also nearly three times as likely as non-Hispanic whites to lack health insurance, and nearly twice as likely to be in only fair or poor health, the same study found.

Despite their relatively high poverty rate, Delgado pointed out, Hispanics are underrepresented in Medicaid, the federal-state health insurance program for the poor. Hispanics make up 7.2 percent of the population but only 5.6 percent of Medicaid recipients. By comparison, blacks, who have a comparable poverty rate, account for 31 percent of Medicaid recipients, more than double their portion of the population.

"Poverty alone is a powerful predictor of risk for young children," said Ann Rosewater, staff director of the House Select Committee on Children, Youth and Families. Schools are "particularly alien places" for Latino families, Rosewater said, because of discrimination, the language barrier and the "extreme shortage" of bilingual teachers. Fewer than 2 percent of secondary school teachers are Latino, she said.

The slowdown in integration of the nation's schools in the past 15 years has further isolated Latino children in school, she said.

In 1972, 56 percent of Latino students were in predominantly minority schools, which tend to have higher dropout rates. By 1980, the proportion of Latino students in such schools had climbed to 70 percent.

"Until there is much more visibility and concern about poverty in Hispanic children in this country," Rosewater said, "I don't think Congress is going to jump up and down and do anything."

But Delgado said the very fact that a conference on Hispanic children took place in the nation's capital is "a major accomplishment for the Hispanic community. The important thing is to say: These are our people. These are our strengths. It's our time now."